Abstract
Numerous harmful characteristics of wastewater containing pyridine chemical have a significant negative impact on human health. Therefore, it is preferred to remove it from effluent. The derivatives of pyridine are 2- and 4-picoline. In this work, an adsorption technique was used to remove 4-picoline from the effluent. Wastewater was treated to remove 4-picoline using the natural adsorbent baggage fly ash (BFA). 4-picoline adsorption rate of 82% was reported at pH 6.22, BFA adsorbent dosage of 4 g/L, and contact time of 6 h. The current investigation found that 85.83% of 4-picoline could be removed at its maximum with BFA at a temperature of 333 K. Investigations were also carried out into how the starting concentration and temperature affected the elimination of 4-picoline. According to the kinetic analysis, the process uses pseudo-second-order rate kinetics. The thermodynamics study also demonstrated that all temperatures could be predicted using the Freundlich and Langmuir equilibrium adsorption isotherm models. It further demonstrated that 4-picoline adsorption on BFA is an endothermic process.
HIGHLIGHTS
This study confirmed that 4-picoline can effectively be removed from wastewater by using baggage fly ash as an adsorbent.
The adsorption kinetics of 4-picoline on baggage fly ash follow the pseudo-second order rate expression.
The Freundlich and Langmuir adsorption isotherm models are best suited for elimination of 4-picoline from wastewater using BFA.
The maximum removal of 4-picoline was found up to 85.83%.
INTRODUCTION
One of the largest problems the world is currently experiencing is wastewater treatment. Industrial wastewater effluents discharge a variety of toxins into water bodies, and organic pollutants are drawing a lot of attention due to the environmental risk associated with their release. Organic molecules are crucially needed in industrial products like pesticides, detergents, plastics, petroleum hydrocarbons, organic solvents, and colors (Ali et al. 2012; Dehkordi et al. 2022). With one C-H group substituted by a nitrogen atom, pyridine is a basic heterocyclic organic molecule that shares structural similarities with benzene. Thomas Anderson, a Scottish scientist, first identified it as a component of bone oil in 1849. Pyridine and its derivatives are very hazardous compounds. They are harmful to human health and effects on kidney, liver, eye contact, immune system, inhalation and reproductive system (Yates 1984; Kirk & Othmer 1996; Lewis 2004; Wu et al. 2021). Between 20 and 200 mg/L of pyridine derivatives are present in industrial effluents (Lataye et al. 2008a). However, the concentration of pyridine contaminants in wastewater must be <1 mg/L (Stern et al. 1997). The 4-picoline, commonly referred to as γ-picoline, is a pyridine derivative (Dilip et al. 2011).
The colorless liquid 4-picoline has an unpleasant odor and produces NOx fumes that are extremely hazardous. Acetone, diethyl ether, and water are all soluble in 4-picoline. 4-Picoline is generally found in industrial effluent that produced 4-vinyl pyridine and subsequent polymers. It is also found in the wastewaters of pyridine manufacturing and pharmaceutical units (Stern et al. 1997; Dilip et al. 2011). Therefore, from an environmental perspective, eliminating 4-picoline from wastewater is quite crucial. Numerous researchers looked into a variety of treatment techniques, including biodegradation (Lee et al. 1994), adsorption (Mohan et al. 2004, 2005; Xia et al. 2018), ion exchange (Akita & Takeuchi 1993), electrochemical oxidation (Niu & Conway 2002), and ozonation (Stern et al. 1997), to remove pyridine derivatives from wastewater. Each treatment method has its advantages and disadvantages. Among various techniques the adsorption process is economical and cost-effective for wastewater treatment (Zhu et al. 2014; Smedt et al. 2015; Xia et al. 2018).
Many organic and inorganic chemicals from wastewater can be effectively adsorbed using natural materials derived from agricultural wastes. The sugar industry produces bagasse fly ash (BFA), an agricultural waste, which is gathered from flue gases discharged from furnaces or boilers. Since the BFA is practically free to use, it is utilized in this work as a natural adsorbent to remove 4-picoline from effluent.
MATERIALS AND METHODS
Adsorbate
4–picoline, i.e. 4-Methylpyridine (Chemical formula, CH3C5H4N), is an organic compound collected from the Modern Science Laboratory located in Nashik city in India. It is one of the three isomers of methyl pyridine. This colorless, pungent liquid is a building block for synthesizing other heterocyclic compounds. The 4-picoline stock solution was prepared by dissolution of 1 mL 4-picoline in 999 mL distilled water. By combining the stock solution with distilled water, the desired concentration of 4-picoline needed for the experiment was created.
Adsorbent
The BFA is a natural adsorbent that was gathered from the Indian district of Ahmednagar's sugar industry. The gathered BFA was properly cleaned in hot water heated to 70 °C before being left to dry outside. Then it was sieved by using standard sieves and BFA particle size was analyzed. Using a MAC bulk density meter, the bulk density of BFA was determined. The proximate analysis of BFA was conducted using the I.S. approach (I.S. method 1984). Additionally, using the Micrometrics software, the Brunauer-Emmett-Teller (BET) method was utilized to calculate the surface area of BFA particles.
Analytical measurements
The highest absorbance of 4-picoline was discovered at 262 nm wavelength when its concentration in the water was measured using a UV spectrophotometer. Its concentration is determined by the linear portion of the curve produced by the absorbance and 4-picoline concentration plot. High concentration samples were diluted with distilled water at a distance from the linear region of a calibration curve. The precise concentration was then determined using the calibration curve's linear section.
Batch adsorption study
Various starting concentrations between 5 and 600 mg/L and temperatures between 303 and 333 K were used in the adsorption tests. 0.1 N NaOH or 0.1 N H2S04 was used to change the pH of the mixture. The desired concentration of 4-picoline from 50 to 600 mg/L was added to 100 mL of each bottle. The 4-picoline solution was then mixed with an equivalent amount of BFA adsorbent, and this mixture was shaken at 150–200 RPM for 6 hours. The sample was promptly filtered, and a UV spectrophotometer was used to analyze the filtrate.
RESULTS AND DISCUSSION
Characterization of BFA adsorbents
Table 1 lists the physicochemical characteristics of BFA, including its bulk density, particle size, surface area, fixed carbon content, moisture volatile matter and ash. The fractional sieve analysis of BFA particles was performed and 32% particles in the size range of −600 to +425 μm and 68% particles of −425 and +180 μm were reported. Also, the CHNSO compositions of BFA were found as follows: C (59.12%); H (0.98%); N (0.00%); S (0.00%) and O (39.90%).
Properties of BFA adsorbent
Properties . | BFA . |
---|---|
Bulk density (kg/m3) | 139.7 |
Fixed carbon content (%) | 46.32 |
BET surface area (m2/g) | 83.11 |
Ash content (%) | 43.6 |
Moisture volatile matter (%) | 7.52 |
Average particle size (μm) | 304.64 |
Properties . | BFA . |
---|---|
Bulk density (kg/m3) | 139.7 |
Fixed carbon content (%) | 46.32 |
BET surface area (m2/g) | 83.11 |
Ash content (%) | 43.6 |
Moisture volatile matter (%) | 7.52 |
Average particle size (μm) | 304.64 |
Influence of starting pH of solution
Generally, when we talk about alkaline hydrolysis, we are talking about nucleophilic substitution processes where the attacking nucleophile is a hydroxide ion. For easier disposal, solid organic debris is frequently converted to liquid form using the hydrolysis reaction. Any contaminant's degradation is impacted by the pH, making it a crucial attribute to investigate. The high rate of hydroxyl radical formation during sonochemical degradation affects the final degree of degradation. It has been observed that it is influenced by the pH of the solution at first (Bai et al. 2009; Daware & Gogate 2020).
Influence of pH0 on the removal of 4-picoline (t = 6 h, C0 = 100 mg/L, T = 303 K and m = 4 g/L).
Influence of pH0 on the removal of 4-picoline (t = 6 h, C0 = 100 mg/L, T = 303 K and m = 4 g/L).
Influence of BFA adsorbent dose
Influence of quantity of BFA adsorbent on the elimination of 4-picoline at t = 6 h.
Influence of quantity of BFA adsorbent on the elimination of 4-picoline at t = 6 h.
Influence of starting concentration and temperature
Influence of starting concentration and temperature on the elimination of 4-picoline (t = 6 h, pH0 = 6.22 and m = 4 g/L).
Influence of starting concentration and temperature on the elimination of 4-picoline (t = 6 h, pH0 = 6.22 and m = 4 g/L).
Influence of a starting concentration and temperature on 4-picoline adsorption at an equilibrium (t = 6 h, pH0 = 6.22 and m = 4 g/L).
Influence of a starting concentration and temperature on 4-picoline adsorption at an equilibrium (t = 6 h, pH0 = 6.22 and m = 4 g/L).
Influence of contact time
Influence time on the removal of 4-picoline (pH0 = 6.22, m = 4 g/L and T = 303 K).
Influence time on the removal of 4-picoline (pH0 = 6.22, m = 4 g/L and T = 303 K).
Kinetic study of 4-picoline adsorption on BFA
In order to measure the concentration of 4-picoline (C1) in the solution at the time (t) for various beginning concentrations, a series of experimental runs were carried out during the initial adsorption period, which was for 1 h. In Figure 5 for t = 30 min, the removal of 4-picoline was 59.8% at m = 4 g/L, T = 303 K and C0 = 100 mg/L. The rate of adsorption reduces as the amount of 4-picoline molecules on the surface of BFA increases over time due to an increase in diffusion resistance. Pore diffusion is thus the process that regulates the rate of 4-picoline adsorption.
To build industrial adsorption columns, a kinetic study of adsorption is required. Therefore, to fit the experimental results, the pseudo-first and second order kinetic models were adopted.
4-picoline adsorption pseudo-first order kinetic model at C0 = 100 mg/L and T = 303 K.
4-picoline adsorption pseudo-first order kinetic model at C0 = 100 mg/L and T = 303 K.
4-picoline adsorption kinetic parameters of pseudo-second order model (C0 = 100 mg/L.)
Kinetic parameters of pseudo-second order . | |
---|---|
ks (g/L. min) . | qe (mg/L) . |
1.47 × 104 | 38.46 |
Kinetic parameters of pseudo-second order . | |
---|---|
ks (g/L. min) . | qe (mg/L) . |
1.47 × 104 | 38.46 |
4-picoline Adsorption equilibrium study
4-picoline Adsorption isotherm parameters
Isotherm equations . | Constants . | Temperatures (K) . | |||
---|---|---|---|---|---|
303 . | 313 . | 323 . | 333 . | ||
Langmuir qe=qmKLCe /(1+KLCe) | KL (L/mg) | 0.021 | 0.028 | 0.034 | 0.045 |
qm (mg/g) | 18.51 | 16.12 | 15.14 | 13.51 | |
R2 | 0.994 | 0.992 | 0.991 | 0.994 | |
Freundlich qe=KFC1/n | KF (L/mg) | 1.112 | 1.141 | 1.153 | 1.062 |
N | 1.38 | 1.68 | 1.79 | 1.51 | |
1/n | 0.724 | 0.59 | 0.55 | 0.65 | |
R2 | 0.997 | 0.997 | 0.998 | 0.998 |
Isotherm equations . | Constants . | Temperatures (K) . | |||
---|---|---|---|---|---|
303 . | 313 . | 323 . | 333 . | ||
Langmuir qe=qmKLCe /(1+KLCe) | KL (L/mg) | 0.021 | 0.028 | 0.034 | 0.045 |
qm (mg/g) | 18.51 | 16.12 | 15.14 | 13.51 | |
R2 | 0.994 | 0.992 | 0.991 | 0.994 | |
Freundlich qe=KFC1/n | KF (L/mg) | 1.112 | 1.141 | 1.153 | 1.062 |
N | 1.38 | 1.68 | 1.79 | 1.51 | |
1/n | 0.724 | 0.59 | 0.55 | 0.65 | |
R2 | 0.997 | 0.997 | 0.998 | 0.998 |
As can be seen from Table 3, the adsorption coefficients for linearity (R2) for both isotherms are determined to be R2 > 0.99. As a result, the equilibrium adsorption at all temperatures may be described by both the Freundlich and Langmuir adsorption isotherms.
Thermodynamic study of adsorption



Thermodynamics parameters for an elimination of 4-picoline
Isotherm . | ΔH° (kJ/mol) . | ΔS° (kJ/mol K) . | ΔG° (kJ/mol) . | |||
---|---|---|---|---|---|---|
303 . | 313 . | 323 . | 333 . | |||
Langmuir | 22.47 | 0.085 | −18.96 | −20.47 | −21.64 | −23.09 |
Freundlich | 1.385 | 0.097 | −29.07 | −30.08 | −31.09 | −32.08 |
Isotherm . | ΔH° (kJ/mol) . | ΔS° (kJ/mol K) . | ΔG° (kJ/mol) . | |||
---|---|---|---|---|---|---|
303 . | 313 . | 323 . | 333 . | |||
Langmuir | 22.47 | 0.085 | −18.96 | −20.47 | −21.64 | −23.09 |
Freundlich | 1.385 | 0.097 | −29.07 | −30.08 | −31.09 | −32.08 |
CONCLUSIONS
4-picoline is a hazardous compound to human health that needs to be removed from wastewater. For the adsorption of 4-picoline, a natural adsorbent is available called BFA. The current investigation discovered that 85.83% of 4-picoline could be removed at its maximum with BFA. Because the active adsorption sites were present, the adsorption rate could be improved by increasing the dose of BFA adsorbent. At 4 g/L adsorption dose and 6 h of contact duration, the highest adsorption of 82% was discovered. The ideal initial pH for removing 4-picoline was discovered to be close to 6.22, and an adsorption rate of 82.11% was discovered. The experimental results were fit with pseudo second order adsorption kinetics. The isotherm models such as Freundlich and Langmuir was used to fit the equilibrium adsorption isotherm. The thermodynamic analysis validated the endothermic nature and showed that the adsorption technique works. BFA is a preferred adsorbent for an elimination of 4-picoline from industrial wastewater.
DATA AVAILABILITY STATEMENT
All relevant data are included in the paper or its Supplementary Information.
CONFLICT OF INTEREST
The authors declare there is no conflict.