Trace the evolution path of pharmaceutical wastewater treatment technology based on a patent perspective

SPC

search path counting

LDA

latent dirichlet allocation

AI

artificial intelligence

AOPs

advanced oxidation processes

MPA

main path analysis

SPLC

search path link count

SPNP

search path node pair

MBR

membrane bioreactor

COD

chemical oxygen demand

BOD

biochemical oxygen demand

EPS

extracellular polymeric substances

DL

deep learning

ML

machine learning

As water scarcity and pollution problems become more acute, the need for wastewater treatment and recycling technologies is becoming more and more prominent (Yang et al. 2021). Since the 1950s, the total population and society have been ageing steadily, which has prompted more and more people to pay more attention to the health of the body, leading to an expanding demand for medicines globally. The global pharmaceutical market has experienced sustained and rapid growth over the decades (Cha et al. 2020), which has led to an increase in pharmaceutical wastewater discharges. Pharmaceutical wastewater is characterized by high toxicity, complex composition, and low biodegradability, some fermentation drug wastewater also contains high concentrations of heavy metal ions, which are difficult to treat industrial wastewater with greater environmental safety hazards (Guo et al. 2018). Due to the complexity of the components contained in pharmaceutical wastewater, pharmaceutical factories generally face the problems of high investment and high cost. Therefore, it is of great significance for enterprises and researchers to understand the development context of pharmaceutical wastewater treatment technology and grasp the frontier of technological development, which is conducive to improving pharmaceutical wastewater treatment technology and accelerating implementation.

At present, scholars' research on pharmaceutical wastewater mainly centers on two aspects: on the one hand, it is about the analysis of different pharmaceutical wastewater treatment technologies. For example, a study of different technologies for chemical synthesis pharmaceutical wastewater, biopharmaceutical wastewater, antibiotic pharmaceutical wastewater, and traditional Chinese medicine wastewater revealed that a single treatment technology makes it difficult to satisfy the requirements of the treatment process for pharmaceutical wastewater with complex compositions (Zhang et al. 2022). Advanced oxidation processes (AOPs) such as photocatalytic oxidation have been proposed to be difficult to generalize for the treatment of fermentation wastewater and pharmaceutical wastewater due to high cost and low implementability (Feng et al. 2022). A study analyzing traditional and emerging processes for antibiotic pharmaceutical wastewater found that AOP systems combined with membrane treatment have advantages in treating antibiotic wastewater (Phoon et al. 2020)

On the other hand, it is about the improvement of pharmaceutical wastewater treatment technology and the discovery of emerging technologies. For example, sulfur-doped g-C₃N₄/ZnO catalysts and hybrid photocatalytic systems were found to be effective in removing diclofenac and tetracycline from wastewater (Gupta et al. 2023). High-performance thin-film composite nanofiltration membranes based on polyvinylidene fluoride prepared using green naringenin-functionalized boehmite (γ-AlOOH@Nar) biomimetic composites were noted to have enhanced fouling resistance and drug rejection properties, which have great potential for application in pharmaceutical wastewater treatment (Moradi et al. 2023).

From the above literature, it can be seen that scholars often focus on one or a few specific pharmaceutical wastewater treatment technologies, but rarely consider the whole picture holistically.

Given the above background, this paper uses the patent data of pharmaceutical wastewater treatment technology, using Pajek software and SPC algorithm to identify the global main path. LDA topic modeling is performed using PYTHON to extract topics from different time windows and determine the topic evolution Sankey diagram based on association rules. Finally, according to the results presented by the two methods, the current development focus of pharmaceutical wastewater treatment technology is summarized, and the future application prospect of the technology is predicted. The rest of this article is organized as follows. The next section describes the research methodology in detail. The third part presents the results of the patent analysis. Finally, discussions and conclusions are presented.

Patent data are one of the largest and most reliable sources of technical information in the world. Although patent data alone may not provide as much background and contextual information as scientific literature, market reports, etc. it contains the most valuable information about a particular product or technology and is a reliable source of data for quantitatively analyzing technology trends. Through patent analysis, we can not only grasp general information about certain technologies, such as technology growth trends and geographical distribution, but also further explore hot themes and technology evolution paths. For example, Kang & Shin (2015) used patent data to identify trends in Light-Emitting Diode technology and predicted future developments. Therefore, in this paper, patent data are used as a data source.

The article selected the Derwent Innovation Index (DII) database, which contains patent literature covering all areas of technology, including 372,000 patent records from 41 major patent publishing organizations worldwide since 1963 (Liang & Zhong 2022), to ensure the accuracy of the results of this study.

This article searched for granted patents using the search strings: ‘TIAB = (((wastewater OR sewage OR waste liquid) AND pharmaceutical) AND (processing OR reuse OR treatment OR control OR removal))’, 13,476 relevant patents from 2013 to 2022 were retrieved. After removing irrelevant as well as duplicated data, 6,253 patents were obtained, which includes the title, abstract, application number, etc.

MPA is a citation-based analysis method proposed by Hummon & Doreian (1989) for revealing the main knowledge flows (Huang et al. 2022), which is important in the detection of scientific and technological development paths. For example, Yu & Yan (2022) analyzed the research frontiers of the Internet of Things in the supply chain by combining the main path with machine learning (ML) and found that the research hotspots in this field are Radio Frequency Identification (RFID) technology, RFID-costed smart manufacturing, cloud services, and smart packaging. MPA consists of three basic steps, namely establishing the citation network, calculating the link weight, and exploring the main path.

A citation matrix is built based on the patent citation relationships, which is imported into Pajek to construct the citation network, in which patents are regarded as nodes, and the citing and cited relationships between points indicate the diffusion of knowledge.

The assignment of network weights is realized by traversal counting algorithms. Traversal counting algorithms usually include Search Path Link Count (SPLC), Search Path Node Pair (SPNP), and Search Path Count (SPC) search (Fan et al. 2013). The SPC algorithm obtains a slightly longer path length and more constituent components, which is suitable for large citation networks (Yu & Yan 2023). It is recommended as the preferred method for MPA (Oh et al. 2023), so in this paper, the SPC algorithm is chosen to calculate the weights. SPC refers to the number of times that any path between the start node and the termination node passes through a certain edge in the patent citation network (Sun et al. 2019).

There is a lot of patent data on pharmaceutical wastewater treatment technology, forming an intricate network of citations, which requires search methods to further identify the main paths of the network. It will help researchers to have a macro understanding of pharmaceutical wastewater treatment technology. Several methods have been proposed to achieve it, such as the local main path, global main path, and critical main path. The global main path is based on the global importance of nodes in the knowledge flow, extracting the paths with the maximum traversal count in the network, which can discover all the important paths in the network and focuses more on the overall importance of knowledge dissemination compared to the local main paths (Liu & Zhou 2019). Therefore, this paper employs a global main path search for pharmaceutical wastewater treatment technologies to help researchers understand the mainstream of research from a macro perspective.

To better understand the process of the main path method, the following example is given: Suppose there is a network with six nodes (A–F), the network structure and traversal counts (traversal counts in brackets) are as follows: A → B (3), A → C (2), B → D (4), B → E (1), C → D (2), D → F (5), E → F (3). The possible paths from A to F include A → B → D → F and A → C → D → F. The sum of the traversal counts is 3 + 4 + 5 = 12 for the path A → B → D → F. The sum of the traversal counts is 2 + 2 + 5 = 9 for the path A → C → D → F. Since the sum of the traversal counts is higher for the path A → B → D → F, the path from A to F is considered the main path.

There are various ways to divide the time window, for example, Kim et al. (2014) have proposed that the time interval for technology evolution analysis is generally five or 10 years, but this is not suitable for all technology fields; Yan et al. (2019) considered the principle of a comparable amount of literature, but it is more subjective; Hao et al. (2024) introduced the life cycle theory into the division of periods of technological topics and used S-curves to represent the stages of technological development, which enhanced the science and accuracy of the period division. Therefore, this paper divides the time window according to the life cycle and the number of patents. The life cycle is divided into the infant, growth, maturity, and decline (Ma et al. 2022) The number of new patents in the infant stage is relatively small, and the slope of the patent quantity curve is close to zero; the number of new patents in the growth stage rises and then stabilizes, and the slope is greater than zero; the number of new patents in the maturity stage shows a trend of rapid growth, and the slope increases further; the number of new patents in the decline stage shows a decreasing trend, and the slope is less than zero.

According to the theory of knowledge evolution and life cycle, the relationship of theme evolution can be categorized into five types: emerging, integration, inheritance, division, and extinction (Li et al. 2022). Emerging: topics that do not exist in the period of t, and emerge during the period of t + 1. Integration: two or more topics in the period of t, and merge into a new topic in the period of t+ 1. Inheritance: topics that exist in the period of t, and still exist during the period of t+ 1. Division: topics in the period of t and are split into two or more new topics in the period of t+ 1. Extinction: topics that exist in the period of t, and do not exist during the period of t+ 1 (Huang et al. 2022).

As shown in Figure 3 and Table 1 an evolutionary trend toward the improvement of different pharmaceutical wastewater treatment technologies and the use of a combination of various technologies, in which low energy consumption, environmental protection, and implementability, are the study's main objectives. For example, CN102358651A (2012) combined membrane separation technology with a Fenton-like method to solve the problems of PH limitation and high operation cost of the traditional Fenton method, which has a good effect. CN102701495A (2012) introduced micro-electrolysis technology to degrade large-molecule organic matter into small-molecule organic matter, combining the Fenton method and ozone-catalytic oxidation method to jointly reduce the load of the subsequent biochemical reaction. This method is highly efficient, but attention should be paid to the problem of filler sloughing that exists in traditional micro-electrolysis technology (Chen et al. 2017). In addition, the patent uses waste iron filings, waste copper filings, and granular or columnar activated carbon as micro-electrolytic filler, which realized the treatment of waste with waste, reducing both investment and treatment costs. However, waste iron and copper chips may release some harmful substances during the reaction process, such as heavy metal ions, etc., which may cause corrosion of equipment and pipelines (Bhagat et al. 2020). The use of an anaerobic biochemical sewage treatment system for simultaneous treatment of high-concentration wastewater and low-concentration wastewater was proposed in CN103011525A (2013), which realized rapid, low energy, and high efficiency in wastewater treatment. CN103739147A (2014), as the first important node in the main path, encompassed a pretreatment method combining advanced oxidation and conventional chemical treatment. The combined use of multiple methods greatly improved wastewater treatment efficiency. Since 2014, the research on pharmaceutical wastewater treatment has become more targeted. Research on pharmaceutical wastewater treatment technologies with different types, components, and contents has gradually increased. For example, CN106219868A (2016) proposed pretreating high-concentration and high-salinity wastewater with ozone-advanced oxidation and evaporative desalination, respectively, before anaerobic treatment to improve efficiency. CN108033649A (2018) used membrane bioreactor (MBR) to treat high-salinity pharmaceutical wastewater, resulting in a significant increase in the removal of Chemical Oxygen Demand (COD) and ammonia nitrogen from pharmaceutical wastewater. CN109231664A (2019) utilized a triple-effect distillation method to separate the salts from the water. The remaining water was sequentially subjected to iron–carbon micro-electrolysis and Fenton oxidation, in which the ferrous ions produced by the iron–carbon micro-electrolysis filler can provide a certain amount of agent for the subsequent Fenton oxidation. This is a good embodiment of the concept of making full use of resources. CN110526517A (2019) proposed a treatment process integrating pretreatment, biochemical treatment, and deep treatment for pharmaceutical intermediates production water, which realized the up-to-standard discharge standard of medicine intermediate production wastewater. CN112851028A (2021) pointed out the activated persulfate oxidation instead of Fenton oxidation as a means of wastewater biochemistry improvement for the chemical synthesis of pharmaceutical wastewater. CN114409196A (2022) presented a treatment method for antibiotic pharmaceutical wastewater. It creatively added a porous zeolite catalyst loaded with metal oxides to constitute a non-homogeneous Fenton oxidation system while creatively introducing compositions containing light and bacteria, yeast, and bacilli as microbial agents to realize efficient removal of antibiotic pharmaceutical wastewater.

In summary, various physical, chemical, and biological treatment technologies have developed rapidly; treatment technology integrating pretreatment, biochemical treatment, and deep treatment has become a research hotspot. At the same time, biopharmaceuticals, chemical synthesis of pharmaceuticals, antibiotics, traditional Chinese medicine, and other different types of pharmaceutical wastewater treatment technology is more targeted.

To make the division of the time window more consistent with the law of technological development, the time period is divided based on the development stage of the life cycle as well as the number of patents.

Then, LDA was used to model the themes of the patent documents for each time window and summarize the theme labels for each theme. Specific information is presented in Table 2.

As can be seen from Figure 6, there is an obvious evolution of the research themes of pharmaceutical wastewater treatment technology, showing four states of integration, inheritance, division, and extinction of the themes.

• (1) Integration: the fusion of T2 and T3 at t1 to T8 at t2 shows the improvement of the MBR and activated sludge technology, focusing on solving the problems of membrane fouling in MBR as well as the large amount of residual sludge in the activated sludge method.

• (2) Inheritance: There are four highly continuous inheritance themes, namely, T0 at t1, T0 at t2, and T5 at t3; T5 at t1, T4 at t2, and T9 at t3; T7 at t1, T3 at t2, and T7 at t3; T10 at t1, T1 at t2, and T4 at t3.

The first evolutionary vein focuses on the use of agents and composite material in wastewater treatment, which has shifted from single-agent treatment to the use of composite agents as well as composite materials. Agents in wastewater treatment are mainly divided into coagulants, flocculants, adsorbents, composite agents, etc. Commonly used traditional coagulants and flocculants include aluminum chloride, ferric sulfate, ferric chloride, and other salt compounds. Emerging coagulants and flocculants include polymeric ferric sulfate, polyaluminium chloride, polyacrylamide, composite-modified lignin, etc. Compared with traditional coagulants, flocculants have a wide range of applications and great economic benefits, which makes them more widely used in wastewater treatment. Activated carbon, as a commonly used adsorbent, improving its adsorption capacity, reducing its own cost, and recycling it have been the key issues in research. From the source point of view, substances with lower cost and wider sources are expected to be popular materials for their production. For example, the use of waste materials such as traditional Chinese medicine residue to prepare active carbon can not only realize the reuse of resources but also reduce the cost of consumption (CN115353104A). Regarding reuse technology, active carbon in-situ adsorption regeneration (CN115805057A), Superheated Steam superheated steam active carbon regeneration (Ying et al. 2022), electro-Fenton regeneration of activated carbon (Bury et al. 2021) have contributed to the reuse of active carbon. For performance, improving the selective adsorption of activated carbon by appropriately incorporating various functional groups on its surface is the focus of research (Akintola & Ayankunle 2023). In terms of alternatives, using less expensive biochar to replace active carbon has become a hot research topic. The composite agents are often composed of multiple components, each of which can be targeted to solve one or more wastewater treatment problems. The use of composite agents has become a mainstream trend due to the advantages of high efficiency, rapidity, stability, and economy. For example, CN109574118A provides a composite agent mainly using bentonite as an adsorbent to remove pollutants in sewage by physical adsorption. The preparation process is simple, low cost, and does not produce secondary pollution. At the same time, nanocomposites have shown great prospects for development in wastewater treatment because of high stability and strong adsorption capacity (Liu et al. 2021). For example, nano Fe₃O₄/Mn₃O₄ composite material can effectively remove organic pollutants in pharmaceutical wastewater, without secondary pollution (CN105776681A). Talc-ferrite nanocomposites have a good effect on the treatment of difficult-to-degrade substances in wastewater (CN104071848A). Iron–zinc nano microsphere micro-electrolysis composite material has high catalytic performance, which can significantly improve the biodegradability of wastewater (CN115888732A).

The second and third pathways focus on pretreatment and deep treatment processes for wastewater, which have changed from simple physical and chemical treatment technology to advanced oxidation treatment technology while paying more attention to the improvement and combination of various methods. The T1 period focuses on the application of physical methods such as evaporation crystallization, membrane separation and filtration, and dissolved air flotation technology. The research on advanced oxidation technologies such as Fenton oxidation, ozone-catalyzed oxidation, electrochemical oxidation as well as photocatalytic oxidation has been strengthened in the t2 period, among which Fenton oxidation and ozone-catalyzed oxidation technologies are the most widely used and more mature while photocatalytic oxidation technology has a better development prospect (Zahmatkesh et al. 2023). The reduction of sludge production and control of reaction conditions have been the focus of research in Fenton oxidation technology. Such as the use of an upflow multiphase Fenton fluidized bed treatment process to reduce the addition of Fenton medicament iron salt (CN114956300A); broadening the pH range of conventional Fenton fluidized beds with Fenton fluidized bed iron oxide carrier catalysts (CN115624974A). In addition, Fenton oxidation and iron–carbon micro-electrolysis are mutually reinforcing chemical reaction processes, the combined use of them can enhance the oxidation effect and improve the efficiency of wastewater treatment, which has become a commonly used joint treatment method. Research on ozone-catalytic oxidation technology mainly focuses on improving ozone utilization. Currently, the use of ozone microbubbling and ozone catalysts has a significant effect in this regard. The research on photocatalytic oxidation technology is primarily concerned with selecting catalytic materials. For instance, CN114931940 proposes a lithium-tin oxide multi-metal doped photocatalyst, which exhibits a high photocatalytic degradation efficiency for halogenated phenol pollutants. Furthermore, the catalyst has a low preparation cost and is suitable for large-scale production. Concentrating on selecting catalysts for advanced oxidation technologies and coupling various treatment technologies has become popular in the t3 period. For example, the method of electric flocculation-ozone-catalytic oxidation-ceramic membrane coupling is used to treat residual drugs in pharmaceutical wastewater (CN115215492A). Deep treatment of high-concentration pharmaceutical wastewater using an organic combination of four processes: intensified Fenton oxidation treatment process, neutralizing, flocculating, and depositing process, and ozone-catalytic oxidation process (CN114702157A). At the same time, the development of new recyclable catalysts with excellent catalytic activity and stability has become a research priority. For example, lignin carbon/bismuth molybdate composite photocatalyst (CN115779889A), foam metal visible light catalyst loaded with a palladium-modified carbonitride (CN115121274A), solid acid catalyst (CN114590881A) are all characterized by environmentally friendly, non-polluting, and good catalytic performance.

The fourth evolutionary vein is directed toward the study of methods for the removal of heavy metal ions from pharmaceutical wastewater, which has changed from the removal of heavy metal ions to the recovery of heavy metal ions. Commonly used treatment methods for heavy metal ions include chemical precipitation, electrolysis, electrodialysis, physical adsorption, and solvent extraction, of which the chemical precipitation method is the most widely used, but in the use of the process need to pay attention to the number of chemicals used to reduce the emergence of the problem of secondary pollution (Zou et al. 2022). Moreover, since the content of heavy metal ions in pharmaceutical wastewater is low (Rana et al. 2014), the adsorption method has obvious advantages in treating trace heavy metal ions (CN109293100A), which makes the adsorption method another important means of treating heavy metal ions in pharmaceutical wastewater (CN110776571A). Microbial extracellular polymers (EPS) consisting of proteins, humic acids, and polysaccharides removed 95.9% of heavy metal ions Pb from pharmaceutical wastewater (Yuan et al. 2022). However, in reality, pollution tends to be compounded, and different heavy metal coexistence conditions can adversely affect the adsorption performance of EPS (Jin et al. 2019). To reduce the consumption of resources and respond to the call for environmental protection researchers have made some efforts to recover heavy metal ions. For instance, online metal ion detectors can be used to separate heavy metal ions from wastewater (CN108455710A). CN109293100A proposes a method of removing and recycling heavy metal ions by ultrasonic–microwave photocatalytic degradation of organic matter, so that the heavy metal ions complexed with the organic matter are released, and then the heavy metal ions are removed and recycled by electron-controlled ion exchange. Although the recycling of heavy metal ions can reduce the pollution of the environment and improve the efficiency of resource utilization, it faces problems such as the high cost of recycling equipment and the secondary pollution that may accompany the recycling process (Wang 2023).

• (3) Division: T8 at t1 is split into T5 and T7 at t2. Nitrogen and phosphorus removal technology has been divided from simple biological treatment into two themes: biotechnology combined with wastewater treatment chemicals and biotechnology combined with chemical precipitation. At the same time, nitrogen and phosphorus removal technology is more concerned with carbon sources and dissolved oxygen control. For example, to solve the problem of competition for carbon sources that exist in microorganisms in the process of nitrogen removal and phosphorus removal, CN106976975A provides a wastewater deep treatment process for enhanced nitrogen and phosphorus removal; T7 is divided into T2 and T8 in the t3 period, nitrogen and phosphorus removal technology is further optimized, with the reduction or non-use of carbon sources becoming a research priority. In the meantime, anaerobic ammonia-oxidizing bacteria and their control of the reaction conditions have been studied, in addition to the treatment of ammonia and nitrogen in wastewater using agents that tend to be environmentally friendly, agents additive device tends to the development of intelligence; T8 is split into T0 and T2 at the t3 period, the selection of membrane materials for MBR and the intelligence of membrane cleaning methods have received concern, while nitrogen and phosphorus removal technology for pharmaceutical wastewater have been further optimized.

• (4) Extinction: T2 and T6 in t2 period disappear in the next time window. Although the application of ultrasound to membrane cleaning has great advantages, it is limited by its high cost and low economics (Arefi-oskoui et al. 2019). Coagulation and precipitation chemical treatment technology as part of wastewater pretreatment or deep treatment is relatively mature, consequently, research on both themes is weaker in the next period (Guo et al. 2011).

In summary, pharmaceutical wastewater treatment technology mainly focuses on the improvement of biotechnology such as MBR, activated sludge, and anaerobic biological treatment. The combination of AOPs with other technologies includes Fenton oxidation, Fenton-like oxidation, electrochemical oxidation, ozone-catalyzed oxidation, and UV-catalyzed oxidation; and treatment of membrane contamination is carried out. The research on agents that are green, recycled, and low cost is done. The control and detection of intelligent technology are used.

Promoting the development of pharmaceutical wastewater treatment technology is conducive to the recycling and utilization of pharmaceutical wastewater, which plays an important role in alleviating the problem of water shortage. The results of the analysis of the technology development trajectory show that pharmaceutical wastewater treatment technology with high efficiency, low energy consumption, environmental protection, and intelligence has become the mainstream trend. Pharmaceutical wastewater treatment technology is still limited by poor applicability and high cost, despite the tremendous progress made in the last decade. Therefore, the next step for researchers and developers is to focus on improving existing technologies and developing emerging technologies to find wastewater treatment technologies with high operability and low resource depletion rates.

Existing individual wastewater treatment technology has the problems of harsh application conditions, high treatment costs, and poor removal effect of harmful substances. Therefore, the combination of multiple technologies has become one of the key research directions in the future. The currently popular technologies include membrane separation and filtration technology, AOPs, microbial technology, etc., among which the combination of AOPs with other technologies has been widely studied. For example, Yu et al. (2020) detailed a novel wastewater treatment technology combining the advantages of biological treatment and photocatalytic reaction methods-photocatalysis and biodegradation, which shows great potential as a low-cost, environmentally friendly, and sustainable treatment technology. Pan et al. (2019) pointed out that membrane technology combined with electrochemical AOPs can significantly improve the removal efficiency of organic pollutants in wastewater, but needs to be further developed due to the fact that it is in its infancy. Priyadarshini et al. (2022) proposed that modified electrochemical oxidation, gamma radiation, and plasma-assisted systems exhibit have good prospects for development because of the high pollutant treatment capacity. Although the advanced oxidation method has a strong ability to decompose organic matter without secondary pollution, it has certain limitations in practical application due to its high preparation cost and low use efficiency (Jia 2024). For this reason, scholars have carried out a lot of research to reduce the application cost and improve the reaction efficiency. For example, Martínez et al. (2018) combined the Fenton oxidation process with a biological sequencing batch reactor for the treatment of pharmaceutical wastewater to reduce the problem of high reaction temperatures and large quantities of hydrogen peroxide required for the Fenton reaction, which resulted in a significant reduction (36%) in the cost per unit volume of wastewater compared to the Fenton process as a stand-alone treatment. He et al. (2019) used a combined ozone-catalyzed oxidation-biological-aerated filter process to treat antibiotic pharmaceutical wastewater. The average removal of COD in the effluent was increased by 66%, which effectively reduced the operating cost of the ozone-catalyzed oxidation treatment unit. CN115121274A presents a palladium-loaded palladium-modified carbon–nitrogen compounds foam metal visible light catalyst with a good effect on antibiotic removal. The catalyst is easy to prepare, low cost, safe and environmentally friendly, suitable for large-scale preparation, and conducive to industrialization. It can be seen that combining different technologies can solve the existing problems of a single technology to a certain extent, and there should be more research on reducing the cost of advanced oxidation technology in the future.

Nanotechnology development brings new vitality to pharmaceutical wastewater treatment. Among the most widely studied nanomaterials in the field of wastewater treatment include metal oxide nanoparticles, carbon nanotubes, and nanocomposites, which have good prospects for development in physical adsorption, catalytic oxidation, and membrane pollution control. In terms of physical adsorption, compared to natural adsorbents and biosorbents, nanosorbents have attracted much attention for their large specific surface area, lower flocculent formation, and accessible active sites for species binding (Rashid et al. 2021). In the field of photocatalysis, nanomaterials play an important role as catalysts. Raza et al. (2022) showed that possessive carbonaceous nanocomposites could be modified to enhance photocatalytic performance by providing superior quality adsorption edge sites, introducing photo electrons movements, interfering with electron–hole pair recombination, and also bandgap tuning or photosensitization, respectively. Yang et al. (2017) reported that for hybrid TiO₂/graphene (GR) derivatives nanocomposites, functionalized GR is most likely better than pristine GR at improving the photocatalytic activity of TiO2/GR-based semiconductor photocatalysts. In the aspect of membrane pollution prevention, Wang et al. (2019a, 2019b) found that carbonaceous nanocomposites have been proven to enhance membrane sensitivity, permeability, or contamination inhibition. Although nanotechnology has been widely used in wastewater treatment, most of the research is limited to the laboratory stage. Therefore, improving the economic efficiency of nanomaterials and expanding more new applications of nanotechnology in wastewater treatment are the next research directions.

Membrane filtration has been widely used in water pretreatment processes (Henthorne & Boysen 2015), but membrane contamination significantly reduces its filtration efficiency (Zularisam et al. 2006), requiring regular cleaning or replacement of membranes, which undoubtedly increases the operating costs of water treatment (Zularisam et al. 2006). Therefore, the prevention and control of membrane contamination has been a topic of concern for researchers, especially in MBR. According to the relevant research, the number of membrane fouling-related papers published accounted for 22% of the total number of MBR papers (Meng et al. 2017). To improve the anti-pollution ability of the membrane, in addition to the selection of nanomembrane materials, scholars have also conducted the following research. In the preparation of membrane materials, some scholars use physical mixing, chemical copolymerization, and other methods to modify membrane materials. For example, Du et al. (2020) developed a novel organic-inorganic composite membrane based on PVDF and inorganic materials. Zuthi et al. (2013) induced the copolymerization of sulfonamide amphiphilic groups with acrylonitrile materials to form a new copolymer membrane material. Both methods enhance the hydrophilicity of the membrane and significantly improve the antifouling performance. In the future, the problem of poor compatibility of physical mixing should be further solved, and at the same time, the research on the method of chemical copolymerization reaction should also be strengthened. Mutamim et al. (2012) found that the pore size of the membrane was the main factor affecting the membrane flux and the turbidity removal rate of wastewater during the treatment of wastewater containing micropollutants. The larger the membrane pore size, the more heavily fouled the membrane is, the faster the flux decays, and the lower the removal rate is. Therefore, it is necessary to select the appropriate membrane pore size according to the size of the pollutants in the wastewater. In the area of membrane cleaning research, Hong et al. (2014) proposed that ultrasonic irradiation can clean the fouled membrane by producing important physical phenomena, including microjet, microstream, and shock waves, which do not cause secondary contamination. However, frequent cleaning is required, which increases the operating cost. Porcellin & Judd (2010) used chemical cleaning methods when physical cleaning did not meet membrane contamination removal requirements. However, the use of chemical reagents may lead to the inactivation of microorganisms in the bioreactor and these adverse effects caused by chemical cleaning will be emphasized in the future. This indicates that future research should focus on the development of more self-cleaning, mechanically robust, low-cost, and highly environmentally friendly membrane materials, as well as the optimization of membrane cleaning methods according to specific circumstances.

Intelligent wastewater treatment technology has become a new opportunity for development. With the progress of science and technology, artificial intelligence (AI) technology has gradually been applied to pharmaceutical wastewater treatment. Intelligent wastewater treatment systems using sensors and monitoring equipment can not only realize real-time monitoring of wastewater quality, flow, and environment, but also according to preset algorithms for automatic adjustment and treatment, which makes the pharmaceutical wastewater treatment process more efficient, accurate, and controllable. For example, CN111977710A proposed an intelligent industrial wastewater treatment system, which, on the one hand, realizes the detection of pollutant components in wastewater, real-time monitoring, and improvement of wastewater treatment, and on the other hand, achieves the purpose of reducing carbon emissions, and saving pharmaceuticals. Lotfi et al. (2019) accurately predicted the removal of COD and Biochemical Oxygen Demand (BOD) conventional pollutants from wastewater using hybrid modelings such as a linear stochastic model and nonlinear outlier robust extreme learning machine technique. Niu et al. (2022), after comparing the accuracy of different AI membrane contamination prediction methods, pointed out that artificial neural networks can deal with environmental problems by solving multivariate nonlinear questions. The time required to solve the target problem is less compared to traditional mathematical modeling, which makes it the dominant algorithm in the field of membranes. Currently, deep learning (DL) and ML are the main means of applying AI technology to wastewater treatment systems. In the future, the use of AI in combination with big data, online databases, cloud computing, and the Internet of Things will become an effective means of further improving the efficiency of wastewater treatment. For example, Su et al. (2020) introduced the Internet of Things into water treatment plants to collect wastewater data, remotely control treated water quality, and monitor the operational status of equipment. This system has the potential to reduce energy consumption and improve economic efficiency. Donovan et al. (2015) developed a cloud-based data collection system for wastewater treatment plants that can be used to monitor and analyze the waste generated. In addition, the application of image-based AI algorithms may be another direction for its development in wastewater treatment (Zhang et al. 2023). For example, Satoh et al. (2021) combined sludge micrographs with DL to provide effective early warning of sludge swelling. Although AI has a significant impact on wastewater treatment, its model training costs are considerable, and the equipment investment costs are high. Consequently, the number of cases in which AI is used in wastewater treatment is relatively limited (CN114648238A).

Based on the patent data of pharmaceutical wastewater treatment technology from 2013 to 2022, this paper analyzes the evolution trajectory of pharmaceutical wastewater treatment technology by using the MPA as well as temporal theme evolution analysis, which reveals its research hotspots and research frontiers in the past decade.

The results and discussion led to the following conclusions: (1) The use of compounding agents is promising. Future research should focus on developing environmentally friendly, low-toxicity, biodegradable agents. (2) Advanced oxidation technology is widely studied in pharmaceutical wastewater. Especially, photocatalytic oxidation has a good development prospect, but it is urgent to solve the cost and stability of its catalyst. (3) Nanomaterials have good development space in water treatment, while further enhancement of their economic benefits is the key to moving them from the laboratory to the real world. (4) AI technology has a good role in the control and detection of water quality. In the future, it can be linked with big data and Internet of Things technology to enhance the effect of the role. (5) Membrane pollution prevention and control is very important to reduce the cost of wastewater treatment. Improvement of membrane materials and optimization of membrane cleaning methods are still important topics in the future. (6) The combination of various wastewater treatment methods is a future research direction, especially the combination of advanced oxidation technology and other methods.

However, this study has some limitations. First of all, the data source is relatively simple, and other data related to technology can be introduced in the future, such as conference reports. Secondly, the LDA model has some shortcomings in topic extraction, and more advanced models such as Word2vec and BETR can replace the LDA model.

The authors received financial support from the control strategy and regulatory considerations of drug and device combination products based on the patented technology trajectory of the scientific research project of the Shanghai Drug Evaluation and Verification Center (No. 2222430097).

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

The authors declare there is no conflict.