Conventional technologies and recent developments in the nanotechnological approach for the remediation of persistent organic pollutants

Persistent organic pollutants (POPs), also referred to as organic substances, exhibit the ability to withstand photolytic, chemical, and biological destruction, allowing them to remain suspended in the air for extended periods (Krithiga et al. 2022). Due to their persistence, long-range transportability, potential for bioaccumulation in fatty tissue, and severe toxicity even in low quantities, POPs represent a significant global hazard, impacting both the environment and human health (Singh et al. 2021). Being transferable by wind and water, POPs can exert their effects far from their point of origin, affecting both human populations and wildlife. They can persist in the environment for extended durations and can accumulate and be transmitted through the food chain, posing risks to successive species.

The post-World War II era witnessed the widespread use of thousands of synthetic compounds, including several POPs, driven by increased industrial manufacturing, and their utilization in industry, crop production, and pest management (Harrad 2009). However, these substances have led to unintended consequences for the environment and human health. The long-range environmental transport and biomagnification of POPs pose significant risks to ecosystems and indigenous populations, particularly in the Arctic (Dapaah et al. 2022), with regions such as the Baltic and Alpine areas serving as examples of European POP sinks.

POPs have been linked to various health issues in both humans and animals, including cancer, immune system disorders, reproductive and developmental problems, and nervous system damage, even at low concentrations (Bernes 1998). The United Nations Environment Programme (UNEP) initiated its study of POPs in 1995, initially focusing on a group of pollutants known as the ‘Dirty Dozen,’ which included highly persistent and harmful compounds such as aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, hexachlorobenzene (HCB), mirex, polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and toxaphene (Jones & De Voogt 1999).

Since then, additional substances have been added to the list of POPs, including certain brominated flame retardants, polycyclic aromatic hydrocarbons (PAHs), and organometallic compounds like tributyltin (TBT) (Alharbi et al. 2018). POP levels tend to increase within the food chain, concentrating in animals at the top of the hierarchy, such as fish, predatory birds, mammals, and humans, posing significant risks of acute and long-term adverse effects. While some POPs are intentionally produced, others, such as dioxins and furans, are byproducts of industrial processes or result from the combustion of organic materials (Fiedler 2002).

POPs have been associated with various specific impacts, including cancer, allergies, hypersensitivity, damage to the central and peripheral nervous systems, reproductive issues, immune system disruption, and endocrine disruption (El-Shahawi et al. 2010). Our research aims to provide a concise, focused review of POPs, highlighting their sources, types, and potential hazardous impacts on living organisms, while also offering insights into detection and monitoring strategies. Additionally, we aim to draw attention to significant conventional removal technologies and recent advancements, including nanotechnology, magnetic nanoparticles, and their synthesis. Finally, we explore the potential of hybrid nanotechnology for POP removal.

POPs are organic substances that persist in the environment for extended periods due to their non-biodegradable nature. These toxic materials, discharged into the atmosphere, water, and soil, significantly impact the economic and social development of civilizations worldwide, primarily originating from industrial and agricultural activities (Ang et al. 2022). Referred to as ‘deadly stealthy attackers’ due to their bioaccumulative and long-lasting characteristics, POPs are ubiquitous in our environment and present in living organisms such as plants, animals, and humans. They are responsible for numerous deadly illnesses and ecological problems, contributing to disorders such as weight gain, diabetes, hormonal disruption, malignancies, cardiovascular issues, reproductive problems, and ecological disturbances. The risks and pollutants associated with POPs pose significant challenges for government agencies, researchers, and non-governmental organizations (Alharbi et al. 2018).

POPs can enter the environment through various mechanisms, primarily originating from human activities. These include agricultural runoff, industrial discharges, urban runoff, sewage systems, atmospheric deposition, and landfill leachate (Kampa & Castanas 2008). Additionally, emissions from residential furnaces, traffic, agricultural pesticides, and evaporation from bodies of water, soil, and landfills contribute to the release of POPs into the environment, along with various industrial sources such as energy production facilities and incinerators (Guo et al. 2019).

Throughout the food preparation process, which includes processing, packaging, shipping, and storage, various steps can introduce POPs into food products (Hung et al. 2022). For instance, POPs present in the environment may contaminate raw materials, and they can be transferred from plants to food through leaf uptake. Moreover, food preparation processes themselves can introduce POPs into food artificially (Batel et al. 2016). POPs vaporize from soils, plants, and water bodies into the atmosphere under specific ambient temperatures, preventing airborne degradation reactions and allowing them to travel long distances before being redeposited. Consequently, POPs accumulate in remote areas far from their sources of origin, particularly in regions like Antarctica and the Arctic Circle where they have never been used (Göktaş & MacLeod 2016).

Because of their slow degradation, POPs persist in the environment, even in locations where they have never been used, continuing to exist in ecosystems years after regulatory restrictions are implemented. Persistent chemicals typically exhibit higher concentrations and are expelled more slowly. Furthermore, POPs exhibit dietary accumulation, or bioaccumulation, whereby they become more concentrated as they move up the food chain and accumulate in specific organs and tissues. This bioaccumulation leads to high concentrations of POPs in species even in remote locations, such as whales, due to long-distance transmission (Windsor et al. 2019).

POPs comprise two significant subgroups: certain halogenated hydrocarbons and PAHs. The latter category includes several organochlorines known for their resistance to degradation, widespread production, use, and persistence (El-Shahawi et al. 2010). The first generation of chemical fertilizers, such as dieldrin, DDT, toxaphene, and chlordane, along with commercial chemical products or byproducts like PCBs, dibenzo-p-dioxins (dioxins), and dibenzo-p-furans, are among the well-known stubborn and bioaccumulative POPs (No 2005). Chlorinated derivatives within halogenated hydrocarbons, particularly those of PCBs, are typically the most persistent. It is known that less chlorinated PCBs are metabolized and excreted more rapidly than highly chlorinated ones and larger chlorinated biphenyls accumulate to a greater extent than lesser chlorinated ones (No 2005) (Figure 2).

The Stockholm Convention accepted and implemented by the UNEP on 22 May 2001 aims to protect the environment and public health from POPs. As of 2014, 179 countries had ratified the convention (El-Shahawi et al. 2010). The convention investigates compounds created through scientific and technological advancements to determine if they can be classified as POPs. At its inception, the convention imposed a complete ban on predominantly toxic and harmful substances, with stakeholders obligated to take action to prevent or reduce POPs released into the environment. Initially, only 12 POPs were recognized for their harmful effects on human health and the environment (Stokke & Thommessen 2013).

Aldrin, in addition to killing wood ants and cicadas, has been considered fatal to humans, birds, and fish, often consumed by humans through dairy and meat products (Zitko 2003). Chlordane, an insecticide used in various agricultural crops and termite eradication, has been found lethal to several bird species, with a half-life in the soil of approximately 1 year (Yadav & Devi 2017). Dieldrin, a pesticide for termite and insect control, has been linked to various health issues, including breast cancer and Parkinson's disease, primarily consumed through food (Zitko 2003). Endrin, a rodenticide, is highly toxic to both humans and aquatic animals, primarily through food exposure (Rahman et al. 2018). Heptachlor, a pesticide for crop pests and mosquitoes, has been demonstrated to have potential carcinogenic effects on humans and negative behavioral changes at low doses, with food being the primary source of exposure (Thakur & Pathania 2020).

HCB, initially used to sterilize seeds, has been linked to various health issues, including colitis and metabolic disorders, with food being the primary source of exposure (Kumar et al. 2013). Mirex, an insecticide used for termite prevention and as a flame retardant, is highly toxic to various species and can accumulate in fatty tissues, primarily through the consumption of livestock meat, seafood, and wild game (Hickey et al. 2006). Toxaphene, used as a pesticide in agriculture and animal husbandry, can persist in soil for up to 12 years and is highly toxic to fish, primarily through food exposure (Mitra et al. 2020).

PCBs, used in various industrial applications, have been associated with spawning failure in fish and impaired fertility in humans, with food being a common source of exposure (Dirinck et al. 2011). Dichlorodiphenyltrichloroethane (DDT), widely used as a pesticide during World War II and later in agriculture, persists in soil for 10–15 years and continues to be a significant source of human exposure through food. Dioxins, byproducts of high-temperature operations, have been linked to various health issues, including birth abnormalities and stillbirths, primarily through exposure to municipal waste and vehicle emissions (Rathna et al. 2018).

Polychlorinated dibenzofurans (PCDFs), similar in hazardous properties to dioxins, are byproducts of processes involving high temperatures and incomplete combustion, with food being the main source of human exposure (Dirinck et al. 2011). Additionally, various flame retardants, brominated compounds, PAHs, and other substances have been added to the list of POPs. Chlordecone, hexabromodiphenyl ether, and pentachlorobenzene are among these compounds, each with specific uses and associated health risks (Smith & Gangolli 2002; Kataoka & Takagi 2013; Jones 2021).

Exposure to POPs can lead to fatalities, chronic diseases, and developmental abnormalities. Some POPs are classified as carcinogenic by the International Agency for Research on Cancer (IARC) and may increase the risk of breast cancer (Ejaz et al. 2004). Additionally, many POPs have the potential to disrupt endocrine functions in the reproductive system, brain, or immune system, affecting immune response effectiveness and increasing susceptibility to infectious and cancerous diseases (Alharbi et al. 2018). Common reproductive consequences of POP exposure include infertility, spontaneous abortion, irregular menstrual cycles, and endometrial issues.

Due to their widespread use in various applications, both historically and presently, people can be exposed to POPs through multiple routes. Nutrition, occupational exposure, and environmental factors are the primary pathways for POP exposure. Approximately 90% of human exposure to POPs not resulting from unintentional or occupational exposure comes from consuming animal products, as they bioaccumulate through the food chain and in adipose tissues (Vizcaino et al. 2014). Most POPs are known to disrupt the normal functioning of the hormonal system. Lower-level exposure to POPs during critical developmental stages, such as fetal and child development, can have long-term effects. In animals, crucial developmental periods occur in the uterus, during ova development, and reproductive seasons. In humans, the critical period of development occurs during fetal development (Carpenter 2011).

POPs can have detrimental effects on health, particularly on the male reproductive system, leading to early puberty, altered sex ratios, and reduced sperm quantity and quality. Female POP exposure has been associated with endometriosis, altered reproductive tissues, and pregnancy outcomes (Abelsohn et al. 2002). Additionally, POP exposure during pregnancy has been linked to changes in newborn birth weight and dimensions, influenced by the mother's weight gain during pregnancy (Sovio et al. 2015). Studies have shown that exposure to certain organochlorine insecticides during pregnancy can impair fetal growth and reduce birth weight, head circumference, and other measurements (Ouidir et al. 2020).

Chemicals that are resistant to environmental deterioration and may endure in the environment for a very long time are classified as POPs. It is crucial to monitor and identify their presence because they may be damaging to both human health and the environment (Guo et al. 2019). POPs, which are harmful substances that can persist for an extended amount of time in the environment, can be found via air and water sampling. They can be detected using samples of air and water collected and examined. Water samples can be taken using grab or composite sampling techniques, while air samples can be gathered using high-volume air samplers (Porta et al. 2008). The presence of POPs is then determined by analyzing these samples in a laboratory using methods like gas chromatography/mass spectrometry (GC/MS) or liquid chromatography/mass spectrometry (LC/MS). It is important to note that the type of POPs being targeted and the intended use of the data will determine the precise sampling and analytical techniques employed.

Analysis of tissue samples can reveal evidence of POPs in animals such as fish and birds. A technique for finding POPs in living organisms like humans, animals, or plants is called biomonitoring. POP concentrations in blood, urine, breast milk, and other biological materials can be determined using biomonitoring. These data can be used to calculate a person's POP exposure as well as to monitor variations in population-level sensitivity patterns over time (Wu et al. 2014). POPs in blood, urine, or breast milk samples taken from people are measured as part of human biomonitoring. To detect the presence of POPs, these samples are examined in a laboratory using methods like gas GC/MS or LC/MS (Augusto et al. 2013). POPs are measured in samples of animal tissue, such as blood, organs, or fat, during animal biomonitoring. They are found in these substances through laboratory analysis employing methods like GC/MS or LC/MS (Odabasi et al. 2015). POPs in samples of the plant body, such as leaves or seeds, are measured as part of the plant's biomonitoring process. They are found in these substances through laboratory analysis employing methods like GC/MS or LC/MS (Ogata et al. 2009).

Using sophisticated equipment, POPs can be accurately detected in soil, sediment, and other materials. GC is a useful instrument for identifying POPs since it can be used to isolate and identify each component of a sample, making it a frequently used method for the identification of POPs. Usually, the specimen is removed first, and then it is put into the GC for analysis (Avino & Russo 2018). A mass spectrometer or another type of detector is then used to find the separated components. This method is frequently used in forensic investigation, industrial quality control, and environmental monitoring (Norli et al. 2011).

Another popular method for finding POPs is high-performance liquid chromatography (HPLC). HPLC is a potent method for isolating and identifying specific components of a sample, much like GC (Sloan et al. 2006). However, HPLC employs a liquid, typically an organic solvent, as the mobile phase as opposed to a gas, making it particularly helpful for the study of polar or high molecular weight molecules. Typically, the specimen is extracted first, put into the HPLC, and separated as it passes through a column filled with a solid stationary phase. Various detectors, including UV-visible, fluorescence, refractive index, and MS, are then used to find the separated chemicals (Ahel et al. 1987).

MS is an effective method for finding POPs. MS is a very accurate and specialized technique that may be used to locate and measure particular molecules in a sample. It is frequently used in forensic analysis, industrial quality control, and environmental monitoring to detect POPs. MS is a crucial instrument for monitoring and reducing the negative impacts that POPs have on environmental factors and human health due to its excellent sensitivity and selectivity in detecting and quantifying minute levels of these pollutants. Examples of MS methods that can be used to find POPs include (i) GC–MS, (ii) liquid chromatography–mass spectrometry (LC–MS), and (iii) inductively coupled plasma-mass spectrometry (ICP-MS) (Kodali et al. 2022).

Rapid industrialization and globalization, now considered essential elements of growth, are meeting the never-ending demands of the expanding human population. While these actions have contributed to the remarkable ascent of human civilization, they have also severely polluted the environment through the release of highly hazardous waste. The distribution of hazardous chemicals, as well as additional non-biodegradable materials, contaminates commercial effluent and the surrounding environment, greatly increased by the expansion of industrial activity (Karthigadevi et al. 2021). POPs are among these toxins that are thought to be detrimental to people, animals, and plants. They originate from sewage from homes, runoff from cities, waste from industries, and agricultural sewage. Sewage cleanup facilities and other sectors such as food fermentation, paper and pulp production, farming, and aquaculture also contribute to their presence (Doll & Frimmel 2005). The dissolved oxygen content of water bodies may be depleted during the breakdown of organic contaminants faster than it can be replaced, leading to oxygen depletion and detrimental effects on aquatic fauna. Large amounts of suspended particulates found in wastewater containing organic contaminants restrict the amount of photosynthetic light available to living organisms, and when they settle out, they alter the characteristics of the riverbed, rendering it unsuitable as a habitat for many species. Examples of organic pollutants include pesticides, fertilizers, hydrocarbons, phenols, plasticizers, biphenyls, detergents, oily substances, lubricants, medications, proteins, and carbohydrates (Kumar et al. 2021). Table 2 provides various methods for removing different particles from aqueous solutions using various techniques along with their efficiency.

Over the past few decades, interest in wastewater treatment has increased due to the need to find solutions that will both improve water quality and protect the environment. Water systems, as well as people, animals, and plants, must be protected from these contaminants and their effects. Wastewater regeneration is the best option to mitigate their impact. To reduce the number of toxins in wastewater, several techniques are used. However, many of these techniques often come with high capital and operating expenses, limiting their application. POPs can be removed through traditional physical, chemical, and biological techniques, including adsorption, flocculation, oxidation, membrane treatment, and biosorbents (Chan et al. 2022).

A soluble chemical (adsorbate) is extracted by reacting with a hard surface, from a liquid during the adsorption process (adsorbent). This approach has a good possibility of eliminating lingering organic and inorganic substances and is frequently used in industry for waste treatment and product separation. Researchers pay a lot of attention to the adsorption technique, which is often used to remove organic and inorganic contaminants from wastewater in industries (Titchou et al. 2021). In recent years, the search for affordable adsorbents with pollutant-binding capabilities has intensified. Natural resources, agricultural waste, and industrial waste are all readily available materials that can be employed as affordable adsorbents. These substances may be combined to produce activated carbon, which can be used to clean water and wastewater by adsorbing contaminants (Pi et al. 2018).

Adsorption is a surface phenomenon that is frequently used to remove both organic and inorganic pollutants. When a mixture comes into close proximity to a solid with a highly permeable surface framework, liquid–solid intermolecular forces of attraction cause a portion of the solute molecules from the solution to be emphasized or deposited at the solid surface (Rashed 2013). It is exothermic, occurs at cold temperatures, greatly resembles the process of condensation, and has a form of adsorption latent heat comparable to that of condensation (Ighalo et al. 2022). Activated carbon contains a large surface area and high capacity for adsorption, making it a common adsorbent material for POP removal. Zeolites, metal-organic frameworks (MOFs), and clay minerals are additional adsorbent substances that can be employed. These adsorbents can be used as granules, powders, beads, and other forms. POPs can be effectively eliminated from the environment via adsorption, but it is vital to consider how to regenerate and dispose of the adsorbent material after it becomes saturated with pollutants (Olivella et al. 2011). The adsorbent can be heated in an oven or chemically regenerated, but this procedure can be costly and potentially unfriendly to the environment. When selecting an adsorbent material and adsorption procedure, it is crucial to take into account the cost and ecological impact of adsorbent regeneration and disposal (Wang et al. 2022).

Activated carbon is a frequently employed adsorbent material for the removal of POPs from liquids, gases, and soil (Katsoyiannis & Samara 2004). It is produced by heating a carbon-rich substance – such as wood, coal, or coconut shells – at a high temperature while exposing it to a gas, which makes the substance porous and increases its surface area (Zhu et al. 2020). Because activated carbon has a wide surface area and is highly pollutant-absorbing per unit weight, it is a perfect POP adsorbent material. The elimination of POPs by activated carbon adsorption is both inexpensive and effective, but it is not without drawbacks. Over time, the adsorbent may become saturated, necessitating regular replacement or regeneration (Ren et al. 2018). Additionally, not all POPs can be efficiently adsorbed by activated carbon; for example, dioxins and furans have a low capacity for adsorption. Therefore, when selecting activated carbon as an adsorbent for POPs removal, it is essential to consider the cost, ecological impact, and efficacy of the adsorbent for the given compound (Ighalo et al. 2022).

Tiny particles in water are brought together during flocculation to generate larger, easier-to-filter or settle particles. It is frequently used in conjunction with filtration and sedimentation methods to eliminate contaminants from water and sewage. By introducing a chemical coagulant, such as aluminum or iron salts, to the water, flocculation can be utilized to remove POPs from water (Shon et al. 2007). POPs are transformed into larger particles known as flocs by the coagulant, which can then be filtered or sedimented out of the water. Although flocculation can be a useful technique for eliminating POPs from water, it has some drawbacks. The specific POPs and the coagulant utilized determine how well flocculation works (Saxena & Bharagava 2015). Some POPs have low solubility in water and are therefore difficult to remove using flocculation. Furthermore, flocculation can result in the production of massive quantities of sludge that could be challenging to remove from the environment and may still include the toxins that have been eliminated from the water (Pariatamby & Kee 2016).

In the flocculation procedure to remove POPs from water, aluminum salts, such as aluminum sulfate (Al₂(SO₄)₃), and aluminum chloride (AlCl₃), are frequently utilized as coagulants. When the surface charge of POPs particles is neutralized by aluminum ions in these salts, flocs, or larger particles, are formed. After that, these flocs can be taken out of the water via filtration or sedimentation (Xing et al. 2010). The individual POPs, the quality of water, and the coagulant dosage all have an impact on how well aluminum salts work as a coagulant to remove POPs. In general, cationic POPs may be removed more effectively with aluminum chloride than anionic POPs with aluminum sulfate. Aluminum salts, it should be noted, may have detrimental effects on the environment. Aluminum salt usage has the potential to raise the amount of aluminum in the treated water, which might be hazardous to aquatic life. Furthermore, the sludge generated during the flocculation process may contain significant concentrations of aluminum and POPs, making safe disposal of it challenging (Shon et al. 2005). Therefore, while selecting aluminum salts as a coagulant for POPs removal, it is crucial to take into account the precise POPs to be eliminated, the water properties, the dosage of aluminum salts utilized, and the discharge of sludge. As an alternative to aluminum salts, iron salts or natural polymers should be considered, as well as the price and environmental impact of their use (Hussain et al. 2013).

Another drawback is that not all types of water lend themselves to flocculation, such as those with high turbidity or high organic debris, which can impair the process. Therefore, while considering flocculation as a method for POP removal, it is vital to take into account the specific POPs to be removed, the water properties, and the disposal of sludge. Large amounts of sludge that are difficult to dispose of and that may include the contaminants that were eliminated from the water due to flocculation can occur. The flocculation technique can be expensive, particularly if the water has high POP concentrations (Laor & Rebhun 1997).

By utilizing chemical or biological agents to dissolve the chemical bonds in POP molecules, which makes them less harmful and easier to remove, POPs can be removed (Farhat et al. 2015). Pollutants are frequently removed or broken down by the process of oxidation. Some oxidation processes, including thermal oxidation, can entirely eliminate POPs and produce byproducts of low toxicity. Methods of oxidation can be used with a range of POPs and tailored to the site's environment and pollution levels (Ritesh & Srivastava 2020).

Oxidation can take several different forms, including thermal oxidation, chemical oxidation, and photochemical oxidation. POPs are oxidized using heat in a process called thermal oxidation. Certain POPs, including polychlorinated biphenyls (PCBs), can be destroyed with this method, but it can also produce additional pollutants and use a lot of energy (Sonawane et al. 2022). POPs may be treated using a variety of thermal oxidation techniques, including incineration, pyrolysis, and thermal desorption. POPs are burned in a very hot furnace that can reach 1,800 °C during the incineration process. POPs can be destroyed very effectively by incinerating them; however, this process can produce other pollutants and use a lot of energy (Yang et al. 2022). The POPs are heated in this procedure without oxygen that induces them to disintegrate into more basic chemicals. Some POPs can be eliminated by pyrolysis; however, it may also produce additional pollutants (Buss 2021). In order to disperse the POPs, which may subsequently be removed and destroyed, this procedure includes burning the contaminated soil or silt. Large contaminated land areas can be treated by thermal desorption, but it uses a lot of energy (Bakir et al. 2014).

POPs are oxidized chemically using substances like hydrogen peroxide, ozone, or potassium permanganate. Many POPs can be destroyed using these techniques, but the chemicals employed can be risky and expensive. The benefit of chemical oxidation is that it can handle a variety of POPs and can be adjusted to different site circumstances and levels of contamination. It is also affordable and has a broad application (Dominguez et al. 2020). However, it calls for the usage of potentially dangerous substances. The specific POPs being treated and the local environmental conditions may have an impact on how well the treatment works. Several typical compounds, including the following, can be employed in chemical oxidation. A variety of POPs, such as PCBs and PAHs, can be broken down using hydrogen peroxide (Doick et al. 2005). Ozone can be used to degrade a variety of POPs, such as PAHs and chlorinated chemicals (PAHs) (Ji et al. 2023). Many POPs, such as PAHs and chlorinated chemicals, can be broken down using potassium permanganate. Sodium hypochlorite substance can be used to degrade several POPs, including PCBs (Zheng et al. 2013).

With the use of light energy, POPs can be broken down into less harmful byproducts through a process called photochemical oxidation (Zacharia 2019). This technique depends on the POPs' ability to absorb light, which triggers chemical processes that result in the destruction of the pollutants. In addition to being energy-efficient and eco-friendly, photochemical oxidation can be used to eliminate some POPs, such as PAHs, without producing any negative byproducts. But it needs a lot of light energy, and it can be constrained by things like cloud cover and climatic conditions (Mejía-Morales et al. 2020). POPs are broken down using this procedure, which also uses hydrogen peroxide (H₂O₂) and ultraviolet (UV) light. By reacting with the POPs and the H₂O₂ to create hydroxyl radicals, the UV radiation causes the degradation of the pollutants. POPs are broken down during this process using ozone (O₃) and UV light (Badmus et al. 2018). The hydroxyl radicals that are created as a result of the UV radiation interact with the POPs and O₃ to destroy the pollutants. In this method, POPs are broken down using sunlight and a photocatalyst like titanium dioxide (TiO₂). The contaminants are degraded by chemical reactions that the sunlight starts on the photocatalyst surface (Basavarajappa et al. 2020).

To extract impurities or pollutants from the desired result, liquid or gas is carried over a quasi-membrane during the membrane treatment method. Water and other liquids can be treated with membranes to eliminate POPs. To eliminate contaminants, the liquid is forced across a membrane that serves as a physical barrier (Mustereţ & Teodosiu 2007). The kind of pollutant, the concentration of pollutant, and the type of membrane utilized are all factors that affect how well membrane treatment works for removing POPs. Reverse osmosis (RO), ultrafiltration (UF), microfiltration (MF), and gas separation are the most used membrane types utilized for POP removal.

Water and other liquids are frequently treated with RO, a membrane-based technique, to eliminate POPs. Under pressure, the liquid is forced across a partially permeable membrane that serves as a physical obstacle to filter out impurities. Typically, a fabricated material with a high POP rejection rate, such as polyamide, is utilized to create the membrane in RO systems for POP removal (Ozaki & Li 2002). The RO process uses pressure to effectively remove the contaminants by forcing the liquid through the membrane. RO is efficient at removing a variety of POPs such as pest control products, dioxins, and PCBs (Xiang et al. 2019). However, the efficiency of RO in eliminating POPs is impacted by the pollutant's chemical composition, its level, and the RO process's operating circumstances (Yoon & Lueptow 2005). It is significant to highlight that some POPs cannot be efficiently removed by RO, necessitating the use of additional treatment techniques such as activated carbon adsorption or biodegradation. To further assure that the treated water is suitable for consumption, post-treatment procedures like disinfection could be required (Mustereţ & Teodosiu 2007).

Water and other liquids can be treated with UF, a membrane-based technique, to remove POPs. In order to remove contaminants physically, the liquid is forced across a semi-permeable membrane as part of the process (Arsene et al. 2011). The membrane employed in UF for POP removal is typically constructed from a synthetic material with a high POP rejection rate, such as polysulfone or polyvinylidene fluoride. The UF method uses pressure to effectively remove the contaminants by forcing the fluid through the membrane (Cheng et al. 2021). It is significant to note that some POP types, such as some dioxins and furans, that possess a greater molecular weight and compact size, might not be effectively removed by UF. Additionally, other treatment techniques such as activated carbon adsorption or biodegradation may be necessary because UF alone might not be enough to remove all POPs (Barjoveanu & Teodosiu 2009).

A technique called gas separation involves passing a mixture of gases across a membrane to extract the individual gases. The membrane is made to selectively permit some gases to move through it while blocking others. The majority of POPs are gases or semi-volatile liquids, and gas separation techniques can be used to remove them from gas mixtures. The efficiency of gas separation in eliminating POPs, however, is based on the specific chemical properties of the contaminant, its concentration, and the gas separation process's operating circumstances (Gu et al. 2011). Making advantage of absorbent or adsorption materials, such as activated carbon or zeolites, is one of the most used ways for gas separation. These substances can bind or accumulate POPs from mixtures owing to their enormous surface areas and gases (Dasgupta et al. 2010). The contaminants can then be thermally desorbed or eliminated from the absorbent by regenerating the adsorbent. A few of the volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) that are present in the POPs are also separated using membrane separation processes including hollow fiber membrane contactors, porcelain membranes, and polymeric membranes. It is significant to note that further treatment techniques, such as catalytic combustion or thermal oxidation, may be necessary since gas separation alone might not be adequate to eliminate all POPs (Norli et al. 2011).

POPs can be effectively removed from aqueous solutions using biosorbents, which are substances derived from natural sources. Examples of popular biosorbents include activated carbon, peat, and various plant materials such as wood and agricultural waste. These substances function by adsorbing the contaminants onto their surfaces, effectively removing them from the solution (Ngo et al. 2015). Biosorption is considered a viable technology for treating wastewater containing POPs due to its low cost, the availability of biosorbents, ease of separating pollutants from the biosorbents, and environmentally friendly nature of the process. Biosorbents employ various methods such as adsorption, precipitation, and chelation to remove contaminants. Because of their minimal cost, ease of separating contaminants from biosorbents, and environmentally friendly characteristics, they are viewed as a promising technology for treating industrial effluents and wastewater. Moreover, biosorbents are more environmentally friendly than many conventional pollutants because they are renewable and biodegradable. They can also be regenerated and reused multiple times. Humic and fulvic acids, abundant in peat moss, lignite, and coal, have the ability to bind to a wide range of organic contaminants (Okoro et al. 2022).

The development of more effective and affordable solutions has been a current push in the elimination of POPs. POPs can be eliminated from the environment using a variety of technologies, such as bioremediation, advanced oxidation processes, and physical–chemical treatment (Sun et al. 2020). The use of chemical oxidizing agents in the presence of the right catalyst and/or UV light to oxidize or degrade the target pollutant allows for the degradation of organic contaminants with a large number of different structures into materials that are less toxic and/or more easily biodegradable. These methods are also referred to as advanced oxidation technologies. Advanced oxidation processes are a class of chemical treatment techniques that reduce POPs in water and the atmosphere by producing highly reactive oxidants such as hydroxyl radicals (Noor et al. 2022). These oxidants can break down a variety of contaminants, such as dioxins, aromatic polycyclic hydrocarbons, and chlorinated chemicals. The hydroxyl radical reacts with organic molecules quickly and generally non-selectively by removing hydrogen, adding to unsaturated bonds and aromatic rings, or transferring electrons (Daramola & Adebayo 2022). Complete decontamination in the case of POPs (wastes) may necessitate the sequential application of many different decontamination technologies, such as a photochemical AOP pretreatment accompanied by a biologically or electrochemical treatment.

Ozone, a highly reactive form of oxygen, is used in the advanced oxidation process known as ozonation to oxidize and destroy POPs in water and the atmosphere. Ozone is a potent oxidant that can degrade a variety of contaminants, including dioxins, PAHs, and chlorinated chemicals (Wang et al. 2018; Yang et al. 2018a). The starting level of pollutants, the pH of the water and air, the temperature, and the length of time that ozone is in contact with the pollutants all affect how effectively ozonation removes POPs (Ikehata et al. 2008). Ozone can remove a variety of POPs efficiently, but it can also leave behind hazardous byproducts that may require additional treatment. For more effective pollutant removal, ozonation could also be integrated with some other technologies including filtration, adsorption, and biological treatment. Ozonation can be done in a number of ways: (i) bubble ozonation technique, which is the most popular, involves bubbling ozone gas through the water or air to be treated, (ii) corona discharge ozonation technique creates ozone using an electric discharge, and (iii) UV ozone technique generates ozone using UV light.

Advanced oxidation with non-thermal plasma (NT-AOP) technique creates highly reactive species like hydroxyl radicals and ozone to break down contaminants in the air and water. Various reactive species, including electrons, ions, and radicals, are present in non-thermal plasma, which is a form of plasma produced at relatively low temperatures (Jiang et al. 2012). The method should be tuned for particular pollutants and applications because the efficiency of NT-AOP is greatly influenced by the type of pollutant, the flow rate, and the discharge conditions. Dielectric barrier discharge (DBD) plasma technique creates plasma between two electrodes that are separated by a dielectric barrier using a high voltage. Corona discharge plasma technique creates plasma via an electric discharge. Gliding arc discharge plasma technique creates plasma between two electrodes using an electric discharge (Jiang et al. 2014).

Fenton's reagent is indeed an advanced oxidation process it produces hydroxyl radicals that can break down POPs in both water and the atmosphere using ferrous ions and hydrogen peroxide. Due to their high reactivity, dioxins, PAHs, and chlorinated chemicals can all be broken down by the hydroxyl radicals (Panizza & Cerisola 2001). The starting amount of pollutants, the pH of the water or air, the temperature, and the length of time that Fenton's reagent is in contact with the pollutants are only a few of the variables that affect how effective the reagent is. Fenton's reagent has the ability to remove a variety of POPs, but it might leave behind hazardous byproducts that may require additional treatment (Hou et al. 2016).

As an oxidizing agent in chemical reactions, Fenton's reagent is a mixture of ferrous ions and hydrogen peroxide. Batch treatment involves adding a predetermined quantity of Fenton's reagent to a quantity of wastewater or another liquid containing the pollutants that need to be eliminated. Hydroxyl radicals, which are extremely reactive and capable of dissolving a variety of pollutants, are produced as a result of the interaction between Fenton's reagent and the contaminants. To maximize the effectiveness of the therapy, adjustments can be made to the temperature, pH, and amount of time the process is allowed to run. Continuous treatment involves adding a stream of Fenton's reagent to wastewater or another liquid that contains pollutants and letting the reaction run continually. This technique is frequently used in commercial settings where regular treatment of large amounts of wastewater is required. Using a recirculation system, where effluent is pushed through a reaction chamber holding the Fenton's reagent and then repeatedly passed through the reactor, is one technique to execute continuous treatment. The reaction conditions can be improved by adjusting the pH, temperature, and residence duration (Panizza & Cerisola 2001).

The employment of living things to remove pollution is known as bioremediation. POPs are hazardous substances that can linger in the environment for a very long time and have a harmful impact on both human health and the ecosystem. Using plants to collect and remove pollutants from the soil, and animals to ingest and remove pollutants from the environment are some of the bioremediation strategies for POPs (Gaur et al. 2018). Microbes are also used to break down pollutants into less hazardous chemicals. It is regarded as an economical and environmentally friendly way to remove pollution. Numerous contaminants, including hydrocarbons, pesticides, heavy metals, and other harmful substances, can be treated via bioremediation. Pollution of the land, water, and air can be treated with it (Padhan et al. 2021). Bioremediation methods all depend on the environmental factors unique to the site and the kinds of pollutants present. The effective remediation of the site can be achieved by combining a number of the various techniques (Tufail et al. 2022).

The study and use of materials on a very tiny scale is known as nanotechnology, usually at the degree of tiny atoms or molecules. Researchers are investigating the use of several varieties of nanoparticles to adsorb, decompose, or eliminate these hazardous substances in the context of eliminating POPs. Nanoscale atom manipulation is the practice of nanotechnology (Fei et al. 2022). Numerous methods in nanotechnology use nanoparticles to effectively and safely provide safe drinking water. Small particles having at least a single dimension in the microscope are known as nanoparticles. They have exceptional optical and electrical properties, unusual physicochemical properties, and a high surface-volume ratio (SVR), making them candidates for cutting-edge uses in electronics, medicine, and the environment (Kharlamov et al. 2008). The surface area of nanoparticles is significantly larger because of their smaller size, which enhances their surface properties and permits chemical reactions to occur on their surface. When compared to other traditional approaches, nano-based procedures offer a cheap solution for wastewater treatment since they are more effective, multifunctional, and demand less reaction time. There are two types of nanomaterials used to remove POPs: metallic (metal and metal oxides; carbon-based nanomaterials; nanocomposites) and nonmetallic (i.e., nanomembranes, polymeric nanomaterials, MOFs, etc.) (Ebrahimbabaie & Pichtel 2021).

One of the most promising ways to modify contaminated treatment technologies is through the use of nanotechnology, which appears to be the biggest blessing for environmental challenges. A novel technique called nanoremediation may be used to safely remove organic pollutants such as pesticides, PCBs, chlorine-based solvents, toxic heavy metals, PCBs, brominated chemical compounds, and other dangerous substances (Ayanda & Petrik 2014). The use of nanoparticles for the cleanup of environmental toxins is known as nanoremediation. Nanomaterials are advantageous for plenty of potential applications as a result of their unique optical, thermal, mechanical, structural, and electromagnetic properties. Physical, chemical, or biological methods can be used to create nanomaterials, which can then be used to make nanoparticles, nanoadsorbents, nanosensors, nanocatalysts, or nanomembranes for wastewater treatment (Reddy 2010).

For the purpose of treating water, nanoparticles have the following qualities: increased surface area and reduced volume; the nanoparticles get stronger, longer-lasting and more durable as the contact area and volume upsurge (Guerra et al. 2018). At the nano level, materials can modify their electrical, optical, mechanical, chemical, or biological properties, facilitating chemical and biological processes. carbon nanotubes (CNTs) have attracted a lot of attention for their usage as water and wastewater filters. Since 1990, CNTs exploration has benefited from its distinct physical, electrical, and chemical capabilities. The most effective technique for purifying water and wastewater was CNTs coupled with electrochemistry (Olushola et al. 2014).

Materials known as nanoadsorbents can attach to or adsorb molecules and ions at the nanoscale. They are extremely effective in absorbing chemicals since they have such a big volume ratio of surface area (Ighalo et al. 2022). They can thus be put to use for many things, such as waste treatment, air purification, and water purification. There are numerous ways to synthesize them, including physical methods, chemical methods, and also methods based on biology (Niu et al. 2012) (Figure 4).

Physical methods entail physically modifying materials to create nanoparticles. To create nanoadsorbents, one can employ a variety of physical techniques. Using high-energy ball milling, materials are ground and milled to create nanoparticles. Although it is a straightforward and economical process, it has the potential to alter the material's structure and produce particles of varying sizes (Piras et al. 2019). In the spray drying procedure, the substance to be manufactured is atomized into tiny droplets, which are subsequently dried to form nanoparticles. It is not appropriate for substances that seem to be sensitive to high temperatures, but it can generate homogeneous and spherical particles. Solvothermal synthesis process uses a solvent along with high pressure and temperature to create nanoparticles (Yang et al. 2007). Although it is a flexible technology that may be used to create a variety of materials, it can also be costly and time-consuming. Supercritical fluid technology involves creating nanoparticles using a supercritical fluid, like CO₂. Although it is a safe and ecologically beneficial process, it can be challenging to regulate the amount and form of the particles that are created. In self-assembly methods, a pattern or a surfactant is used to direct the production of nanoparticles. It is a straightforward and adaptable process that can be used to create a variety of substances, but it can be challenging to regulate the size and form of the particles that are generated (Hamley 2003).

Chemical methods involve creating nanoparticles using chemicals. Nanoadsorbents can be created chemically using a variety of techniques. In chemical reduction, metal ions are reduced to create metal nanoparticles. It is a straightforward and adaptable process that can be used to create a variety of substances, but it may be challenging to regulate the size and form of the particles that are generated. In chemical precipitation, a substance is precipitated out of a solution to create nanoparticles (Panigrahi et al. 2004). Although it is a straightforward and affordable approach, it can be challenging to manage the volume and nature of the particles that are created. The sol-gel method uses the dissolution and polycondensation of precursors to create nanoparticles. Although it is a flexible approach that may be used to create a variety of materials, it can also be time-consuming and necessitate close attention to the reaction circumstances (Iravani et al. 2014). Surfactants are used in the microemulsion method to create stable concentrations of nanoparticles. It is a straightforward and adaptable process that can be employed to create a variety of substances, but it might be challenging to regulate the size and form of the particles that are generated. Electrochemical methods create nanoparticles by using an electric current. Although it is a flexible process that may be used to create a variety of materials, it can also be expensive and call for specialist equipment (Reverberi et al. 2016).

Biological methods involve creating nanoparticles using microbes or enzymes. Nanoadsorbents can be created biologically using a variety of techniques. Microbial synthesis uses microorganisms like bacteria and fungus to create nanoparticles. It is an easy and sustainable process that may be used to make a variety of materials. The enzyme-assisted synthesis method also uses microorganisms like bacteria and fungus. It is an easy and sustainable process that may be used to make a variety of materials (Gudikandula & Charya Maringanti 2016). In the plant-mediated synthesis technique, nanoparticles are created using plant extracts or substances produced from plants. Although it is an easy and ecologically benign process that can be employed to create a variety of materials, it can be challenging to regulate the size and form of the particles that are created. Biosynthesis nanoparticles are created using living cells like yeast or bacteria. The microorganisms are genetically altered to express particular proteins or enzymes necessary for the production of nanoparticles. Peptides, which are condensed sequences of amino acids, are used in peptide-mediated synthesis to create nanoparticles. It is an easy and flexible process that may be used to create a variety of materials. Remember that the required characteristics of the nano-adsorbent and the intended application will determine the synthesis process that is used. The biological approaches could also be more difficult to handle and come with scalability and reproducibility issues (Thakkar et al. 2010).

POPs can be effectively removed from water and air through adsorption using nano carbon, such as activated carbon. The term ‘nano carbon’ encompasses various carbon-based substances with particles that are on the nanoscale, typically smaller than 100 nm. Buckytubes, also known as CNTs, are cylindrical carbon molecules with unique properties that make them suitable for a wide range of commercial applications (Roth et al. 2016). These materials are efficient at capturing and extracting contaminants from the environment due to their large surface area and high adsorption capacity. CNTs are particularly effective for certain pollutants because they exhibit high selectivity for some POPs. However, the application of nano carbon for POP removal is still in its early stages, and further research is needed to fully understand both its advantages and disadvantages. Graphene and fullerenes are two common forms of nanocarbon (Yang et al. 2018b).

Graphene consists of carbon atoms arranged hexagonally in a single layer. It is the building block of various carbon structures, including fullerenes and CNTs. With its enormous surface area, graphene finds utility in industries such as water purification, energy storage, and catalysis (Zhang et al. 2020). Graphene oxide, a derivative of graphene, is particularly useful due to its excellent adsorption capacity and chemical stability. It has been explored for its potential to remove POPs from both air and water. Graphene has demonstrated excellent adsorption capabilities for contaminants such as PCBs, dioxins, and pesticides owing to its large surface area and chemical stability (Wu et al. 2022a).

Fullerenes constitute a family of carbon nanomaterials composed of carbon atoms arranged in elliptical or spherical shapes. They offer promising materials for various applications, including water filtration, due to their unique properties such as large surface area, chemical resistance, and ability to encapsulate other molecules (Gupta & Saleh 2013). Fullerenes have also been investigated for their potential to remove POPs from water, similar to graphene. Certain POPs, such as PCBs and PAHs, have shown a strong affinity for fullerenes (Shoeib & Harner 2002). Fullerene-based adsorbents have demonstrated effectiveness in removing POPs from water, and ongoing research aims to enhance their performance and explore new applications. However, it is important to note that further investigation is needed to understand the long-term behavior of these adsorbent materials and evaluate their potential environmental impacts. Additionally, the synthesis of fullerenes comes at a relatively high cost (Pan et al. 2020).

Nanometer-sized cylindrical formations known as nanotubes typically have diameters ranging from 1 to 100 nm. They can be composed of various substances, such as metal oxides, carbon, and boron nitride, and have been explored as a potential means of removing POPs from the environment (Yao et al. 2016; Wu et al. 2022b). POPs are a class of compounds that can accumulate in the atmosphere and living organisms, posing risks to both public health and the ecosystem. They are also resistant to decomposition. CNTs, due to their large surface area and chemical resistance, are highly effective at absorbing pollutants and are therefore an appealing option for POP remediation (Agasti et al. 2022). Another type of nanotube is boron nitride nanotubes, which share characteristics with CNTs but are more durable at high temperatures and less prone to oxidation. They may find applications in radiation protection, electronics, thermal management, and aerospace.

CNTs are typically categorized into three types based on the number of tubes contained in their structures: single-walled CNTs (SWCNTs), double-walled CNTs (DWCNTs), and multi-walled CNTs (MWCNTs) (Chae et al. 2005). Single-walled carbon nanotubes (SWCNTs) consist of a single layer of wrapped carbon atoms arranged cylindrically. They can reach lengths of several micrometers, with diameters typically ranging from 1 to 2 nanometers. SWCNTs exhibit unique electrical, optical, and mechanical properties, making them useful in numerous applications (Li et al. 2013; Murgolo et al. 2015). SWCNTs have been found to be efficient adsorbents for pollutants such as PCBs, dioxins, and pesticides due to their large surface area and chemical stability. Research indicates that SWCNTs have a high capacity for POP adsorption and can be easily synthesized and functionalized to enhance their selectivity for specific pollutants (Chen et al. 2016). However, it is essential to investigate the potential environmental and health risks associated with their use, as SWCNTs have been shown to have adverse effects on certain cells and organisms. They are also being explored for use as catalysts and water purification agents due to their large surface area (Yang et al. 2013). Further research is needed to fully understand the efficacy of SWCNTs for eliminating POPs and to assess any potential risks associated with their use (Sapkota et al. 2019).

Double-walled carbon nanotubes (DWCNTs) consist of two concentric layers of carbon atoms wrapped into a tube shape. Although they share many characteristics with SWCNTs, DWCNTs are chemically more stable and can withstand harsh conditions such as high pH and elevated temperatures (Moore et al. 2015). DWCNTs have been investigated for their ability to remove POPs from water and air, demonstrating efficient adsorption for pollutants such as PCBs, dioxins, and pesticides due to their large surface area and chemical stability (Peigney et al. 2001). However, further research is needed to fully understand their efficacy and potential environmental impacts (Fujisawa et al. 2016).

Multi-walled carbon nanotubes (MWCNTs) are composed of multiple layers of rolled-up carbon atoms, with diameters typically ranging from 5 to 20 nm. Unlike SWCNTs, which consist of a single layer of carbon atoms, MWCNTs can have multiple layers, providing them with high electrical, thermal, and mechanical conductivities (Li et al. 2011). MWCNTs have been investigated for their ability to remove POPs from water and air, showing high adsorption capacities for pollutants such as PCBs, dioxins, and pesticides due to their large surface area and chemical stability (Aryal et al. 2008). Reports suggest that MWCNTs have superior pollutant adsorption capacities compared to SWCNTs or DWCNTs due to their greater surface area and defects, which can serve as catalytic sites for contaminant adsorption (Liu et al. 2004). Further research is needed to explore their potential applications and environmental implications. Table 3 provides various techniques for removing contaminants from aqueous solutions using MWCNTs, along with their efficiency.

Materials with magnetic and adsorption capabilities are known as magnetic nanoadsorbents. They are typically made of adsorbent materials, such as activated carbon or polymers, covered with magnetic nanoparticles, such as magnetite or magnetically enhanced clay. The adsorbents are reusable and simple to handle due to the magnetic characteristics of the nanoparticles, which make it easy to separate the sorbent from the gas or liquid stream (Gutierrez et al. 2017; Ighalo et al. 2022). POPs can be removed from both air and water streams using magnetic nanoadsorbents. POPs are a class of chemicals that are challenging to break down and can harm both people and the environment. They consist of substances like dioxins, PCBs, and PAHs (Gómez-Pastora et al. 2014). POP-specific adsorbents are often coated on magnetic nanoparticles, such as magnetite or magnetically altered clay, to create magnetic nanoadsorbents for POP removal. POPs can be effectively removed from water, for instance, by coating activated carbon with polymeric adsorbents like polyethyleneimine (PEI) or polyvinylpyrrolidone (PVP) (Peralta et al. 2020). Table 4 provides the adsorption techniques to remove contaminants from aqueous solutions using magnetic nanoadsorbent along with its efficiency.

It has been demonstrated that PEI is efficient at eliminating POPs both from water and the air. Electrostatic interactions enable the cationic polymer PEI to bond to anionic POPs. To make magnetic nanoadsorbents for POP removal, PEI can be utilized as a covering on magnetic nanoparticles like magnetite or magnetically modified clay (Gómez-Pastora et al. 2014). It is simple to remove the material that serves as an adsorbent from either medium or gas stream through the use of an electromagnet. For a variety of POPs, including PCBs, PAHs, and dioxins, PEI has been described as an effective adsorbent (Liu et al. 2020). Different molecular weights and levels of cross-linking can be used to produce PEI, enabling the customization of its adsorption ability for various POPs. Natural organic matter (NOM), which can interact with POPs on adsorbent surfaces, can also be absorbed by PEI, which may limit PEI's ability to absorb POPs (Fei et al. 2022).

It has been demonstrated that the polymeric adsorbent PVP is efficient at removing POPs from both water and the air. PVP is a water-soluble polymer that can form inclusive complexes with lipid-soluble substances as well as hydrophobic interactions to bind to POPs. To make magnetic nanoadsorbents for POP removal, PVP can be applied as a coating to magnetic nanoparticles like magnetite or magnetically modified clay (Liu et al. 2020). For a variety of POPs, including PCBs, PAHs, and dioxins, PVP has been reported to be an effective adsorbent. For improved POP adsorption, PVP may also be derivatized with various groups (such as amine or carboxyl). However, PVP shares several constraints with PEI. For instance, PVP might not be specific for specific POPs, which means that it might also absorb other kinds of pollutants (Tanhaei et al. 2016).

A family of metal ions or clusters is connected by organic bonding agents to form highly porous substances referred to as MOFs (Tchinsa et al. 2021). They can be used for various operations, including gas preservation and segregation, catalysis, and sensing. By adjusting both metal ions and the organic linkers utilized during their synthesis, MOFs can have their characteristics customized. MOFs are desirable for adsorbing these kinds of compounds due to their high contact areas and variable pore diameters (Wagner et al. 2021). Researchers have created MOFs with particular functional groups like carboxyl and amine groups that are recognized to react with POPs. These functional groups have the ability to absorb POPs through electrostatic or hydrogen bonding interactions. Studies have shown that MOFs can absorb over 90% of POPs present in water, demonstrating their efficacy in POP removal. To evaluate their long-term durability and effectiveness in practical applications, MOFs for POP elimination are still in the research stage and require additional investigations (James 2003).

MOFs come in a variety of forms, each with special characteristics and possible uses. POPs can potentially be retrieved from water by using this, which has been examined as a possible adsorbent. MOFs of the type known as zeolitic imidazolate frameworks (ZIFs) are made of metal ions (usually Zn or Co) and imidazolate linkers (Song et al. 2018). They are desirable for the adsorption of POPs due to their excellent stability, heat resistance, and variable pore size. ZIFs have been discovered to be especially effective at eliminating hydrophobic POPs, such as PCBs and PAHs. ZIFs' capacity for regeneration and reuse is one benefit of employing them for POP removal (Phan et al. 2009). MOFs with interpenetrating networks (MILs) are appealing for the adsorption of POPs due to their unique structure, which allows for an immense surface area and varied pore size (Gong et al. 2016). The excellent durability and ability to withstand degradation of MILs, which enable repeated usage without a reduction of adsorption activity, are one benefit of utilizing them for POP removal (Luo et al. 2012).

Porous coordination polymer networks (PCPNs) are appealing for POP adsorption because they are made of strong interactions between ions of metals and organic connectors, which produce a high porosity with a significant surface area and variable pore size (Robin & Fromm 2006). PCPNs have a high degree of stability, allowing for prolonged use without losing adsorption capacity, which is advantageous when used for POP removal. Furthermore, the advantage of allowing them to be reused numerous times, and they are simple to separate from the contaminants they adsorb (Medishetty et al. 2013).

The possibility of using covalent organic frameworks (COFs) as a material for the eradication of POPs from the atmosphere has been investigated. COFs are desirable substances for such adsorption and elimination of POPs from polluted water and air as a consequence of their extensive surface area and flexible porosity. A family of porous materials known as COFs is composed of organic basic components that are joined by covalent bonds (Feng et al. 2012). They are made utilizing a variety of techniques, including solution-based, solid-state, and gas-phase techniques. COFs can be synthesized and characterized using chemical compounds that are unique to the target POPs. For the adhesion of PCBs and PAHs, for instance, scientists have created COFs containing amino and carboxyl groups, accordingly (Waller et al. 2015).

In order to potentially adsorb and remove particular POPs from the environment, COFs with amino and carboxyl groups have been created. It has been discovered that COFs with amino group functionalization are efficient at trapping PCBs. Before being outlawed due to the dangers they posed to the wellness of people and our surroundings, PCBs were a class of toxic, long-lasting compounds that were frequently employed as lubricants and coolants in industrial settings (Jung et al. 2011). It has been discovered that amino-functionalized COFs have a high capacity for adsorbing PCBs and are selective for particular isomers of the chemical. An amino-functionalized COF showed a PCB adsorption ability of approximately 260 mg/g. It outperforms traditional adsorbents like activated carbon by a significant margin, according to one study (Liu et al. 2022).

POPs have been investigated as promising materials for removal from the environment using COFs with carboxyl groups. Because of the presence of carboxyl groups in its framework that can operate as electron-poor sites, it has been discovered that carboxyl-functionalized COFs have a high capability for adsorption toward specific kinds of POPs, also including PAHs (Guo et al. 2020). It has been discovered that carboxyl-functionalized COFs have a strong PAH adsorption capability and are selective for particular isomers of the chemical. Other POPs such as pesticides, dioxins, and insecticides have also been proven to be effectively absorbable by carboxyl-functionalized COFs. With the contaminants, the carboxyl units on the COF may interact electrostatically and through hydrogen bonds (Li et al. 2019).

In order to generate novel materials or systems with distinctive features, hybrid nanotechnology corresponds to the blending of various types of nanotechnology. For instance, the synthesis of novel biomaterials with enhanced characteristics can be achieved by mixing biological and inorganic nanoparticles. POPs have been looked at as potential candidates for eradication from the environment using hybrid nanotechnology. Hybrid nanotechnology toward POP removal is a potential field of research; however, additional investigation is necessary to completely comprehend the processes of separation and to strengthen the efficiency of the materials. Combining a sorbent substance, such as activated carbon, with a catalytic material, including metal nanoparticles, to generate a hybrid sorbent material is one method of applying hybrid nanotechnology for POP removal (Anandan et al. 2020). The hybrid material can be made considerably more potent at removing POPs when mixed with a catalytic substance, such as metal nanoparticles. By triggering chemical mechanisms at the activated carbon's surface, the catalytic material can improve the adsorption and destruction of the contaminants. Palladium nanoparticles are an illustration of a catalytic substance that is utilized in conjunction with activated carbon. When coupled with activated carbon, palladium acts as a catalytic material to initiate processes that degrade pollutants including PCBs and PAHs. Another example is the application of low-valent iron and activated carbon nanoparticles to break down POPs like organochlorines and organophosphates (Rani & Shanker 2018).

Another strategy for POP removal involves using biogenic inorganic hybrid nanocomposites, which combine biogenic components like microbes, enzymes, and proteins with inorganic components like metal nanoparticles. The utilization of enzymes immobilized on metal nanoparticles is one instance of biogenic inorganic hybrid nanocomposites. PCBs and PAHs are just two examples of pollutants that can be degraded by enzymes, which are catalytic proteins. Enzymes can be stabilized and have their activity increased when they are immobilized on metal nanoparticles. The utilization of microbes immobilized on metal nanoparticles is another illustration. Numerous contaminants can be naturally degraded by microorganisms, and when immobilized on metal nanoparticles, their action and stability can be increased (Vázquez-Núñez et al. 2020). It is significant to remember that this strategy remains in the research stage, and additional research is required to completely comprehend the removal mechanisms and to maximize the effectiveness of the materials. Before use, the toxicology and safety aspects of these hybrid nanocomposites must also be considered and assessed (Raza et al. 2022).

In the future, monitoring the environment for POPs is crucial, and measures must be taken to halt their discharge. This involves improving waste management procedures, gradually phasing out the usage of POPs, and developing new, less harmful substitutes. Hence, it is critical to persuade people to take action to lower their exposure by increasing public awareness of the dangers of POP exposure. A comprehensive and coordinated approach at the national and international levels is needed for the management and eradication of POPs.

This concise review of POPs emphasizes their sources, types, and potentially hazardous impacts on living organisms, while also offering observations on detection and monitoring strategies. It highlights significant conventional removal technologies and recent developments, including nanotechnology and magnetic nanoparticles, and their synthesis. Finally, hybrid nanotechnology for POP removal is investigated to safeguard against the harmful effects of POPs on the ecosystem and human well-being. Further efforts must be made to put these conventions into action and reinforce additional protective measures.

The purification, analysis, and use of novel enzymes in the biological remediation of POPs can be facilitated by employing genome sequencing techniques, despite being time-consuming. In conclusion, minimizing energy use and avoiding the generation of secondary contaminants during the remediation process are significant directions for every individual technology developed. Expanding studies on nanoparticle substances, bridging the gap between laboratory studies and real-world use, achieving complete POP degradation, and investigating the decomposition of additional POPs in various environments are essential for achieving the ultimate goal of eradicating POPs from the atmosphere. Nanomaterials are of tremendous interest for cleaning up contaminants from industrial effluents due to their unique features. Therefore, creating hybrid nanoparticles capable of either completely breaking down pollutants or converting them into less harmful forms is necessary.

B. S. R., V. K., S. S. investigated the article, developed the methodology, and wrote the review and edited the article. P. S. K. conceptualized the whole article, validated the data, and supervised the article. G. R. conceptualized the whole article, arranged the resources, and rendered support in formal analysis.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.