wastewater treatment

Water pollution, particularly from industrial dyes, poses a significant threat to the environment, making effective wastewater treatment essential. Waste from walnut shells, previously considered a byproduct, has now gained considerable attention. This study investigates walnut shell-activated carbon as a natural adsorbent for removing fuchsin dye, a major contributor to water pollution. The activated carbon demonstrated high efficiency, achieving a removal rate of 99.10% under optimal conditions (pH 8, contact time 10 minutes, initial dye concentration 10 mg/L, adsorbent dosage 2 g/L, temperature 50 °C). The adsorption kinetics of fuchsin dye on walnut shell activated carbon demonstrated adherence to a pseudo-second-order model (R2 = 0.9999), indicating that the adsorption is chemical in nature. Isotherm studies further revealed a better fit to the Langmuir model (R2 = 0.9969). The maximum adsorption capacity for fuchsin at optimal concentration was found to be 45.45 mg/g. Additionally, thermodynamic parameters such as ΔG°( -1.32 to -10.77 kJ/mol), ΔH°( 50.47 kJ/mol), and ΔS°(0.18 kJ/mol·K) were determined. The thermodynamic analysis showed that the adsorption of fuchsin dye increases with the temperature of the adsorbent, suggesting that the process is endothermic. These findings underscore the potential of walnut shell-activated carbon as an effective and sustainable solution for treating dye-contaminated wastewater and promoting environmentally friendly practices in industrial waste management.

The aim of this study was to prepare a modified type of MOF to remove pollution from wastewater. In the present work, a new composite was prepared using metal-organic framework MIL-53(Al)-(NH2) and polyaniline (PANI). Accordingly, MIL-53(Al)-(NH2) was first prepared using a fast water-based method. Then, using the synthesized MOF, MIL-53(Al)-(NH2) @PANI composite was prepared. The characterization of these synthesized materials was done by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Then, a methylene blue solution was chosen as a sample solution containing dye that commonly exists as a pollutant in industrial and urban wastewater and its removal was investigated with the help of MIL-53(Al)-(NH2) @PANI. The effect of different parameters from the amount of absorbent, color concentration, optimal removal time, and acidity of the environment were investigated with the help of fractional factorial experimental design method . Afterwards, under the optimal conditions obtained, the efficiency of MIL-53(Al)-(NH2) @PANI for removal of methylene blue from a real wastewater sample was investigated by spike method. The results showed that the adsorbent value of 0.08 g/L was chosen as the optimal value. According to the results of the tests, the concentration of 50 ppm methylene blue was chosen as the optimal concentration. PH= 5 and time of 30 minutes showed the best performance of the adsorbent material. The adsorbent showed relatively good reproducibility.

The present research investigated the Photo-Fenton process's effect on Naphthalene's decomposition in petroleum wastewater. The research was conducted on a laboratory scale and in a discontinuous manner. The effect of pH (2, 4.5, 7), Fe2+(5, 42.5, 80 mg/L), H2O2(50, 425, 800mg/L), UV (8, 16, 24 w in the wavelength 254 nm), and time (10, 65, 120 min) on the removal of Naphthalene       (10, 40, 70 µg/L) in synthetic wastewater was investigated. All the experiments were done continuously in 1-liter Erlenmeyer flasks at a constant speed of 300 rpm and at room temperature. To investigate the effect of independent variables on the efficiency of Naphthalene removal, the response surface method was used on the box-Behnken design and based on a 6-variable in three levels with three central points, 54 experiments were designed and executed. The research results showed an increase in the initial concentration of H2O2, and the removal efficiency of Naphthalene from the wastewater also increased. At the concentration of 750 mg/L, the decomposition and removal of Naphthalene increased up to 93.6%. The optimal limit of Fe2+ concentration in removing Naphthalene from wastewater was also determined at 42.5 mg/L. The removal process of Naphthalene from wastewater was also improved in acidic pH (3). The removal of Naphthalene has also increased in the 24w light range and has reached 91.4%. The results of investigating the effect of reaction time showed that the percentage of Naphthalene decomposition and removal has also increased, and the best efficiency was reached in 80 to 100 minutes. Notably, a negative correlation was observed between Fe2+ concentration  and UV radiation on removing Naphthalene. Finally, in optimal conditions, the removal efficiency of Naphthalene using the Photo-Fenton method is estimated to be more than 98%. The present research results show the optimal efficiency of the Photo-Fenton process in the decomposition of Naphthalene.

The Autothermal Thermophilic Aerobic Digestion (ATAD) process stands as a modern wastewater treatment method used for sludge digestion. This process uses thermophilic microbes, such as Thermotogaceae and Clostridiaceae, to break down organic waste naturally without needing external energy sources. This makes it a good way to stabilize the waste, by degrading it into simpler biochemicals through endogenous respiration. Despite its effectiveness, this process is complex, involving microbiological, thermodynamic, biochemical, and kinetic intricacies. This study delves into the kinetics aspect, acknowledging the potential operational setbacks arising from inadequate comprehension. The investigation emphasizes the intricate nature of the biokinetics, encompassing diverse bioreactions related to microorganism growth and sludge digestion. Recognizing the challenges of classical modeling approaches, the paper advocates for artificial neural networks (ANNs) as a promising alternative, citing their ability to handle complex and non-linear data structures. The study used kinetic data to construct an optimized ANN model predicting the kinetic rate constant (KATAD). The model was further tuned with the genetic algorithm (GA), which is a well-known nature-inspired optimizer, to demonstrate exceptional accuracy (more than 99%). Model evaluation using causal index (CI) showed that temperature (TATAD) was the most influential parameter (CI = 1.23), followed by the primary to secondary sludge ratio (P/S) parameter (CI = -0.47), and secondary sludge concentration (Cs) with the least impact on KATAD (CI = 0.19). This research presents a novel study exploring the kinetics of the recently developed ATAD technology. Moreover, it used a cutting-edge approach to tackle the complexities of ATAD. This work advances our understanding of ATAD kinetics and lays the groundwork for improved wastewater treatment strategies. The successful application of the ANN-GA model paves the way for more accurate and effective treatment processes.

In the present study, (Ni0.25Cu0.25Zn0.5) Fe2O4 nanocomposites were synthesized through a co-precipitation method. They were characterized by Fourier-Transform InfraRed (FT-IR) spectroscopy, Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD) analysis, and point of zero charge (pHPZC) techniques. XRD analysis revealed mixed cubic and orthorhombic crystal structures in the nanocomposites. Surface charge was determined by the pH drift method, and the pHPZC was determined to be 6.1. The Optimum Operating Parameters (OOPs) for the adsorptive removal of dye including adsorbent amount (40 mg), concentrations of Congo Red dye (16.0 mg/L), pH (4.5), temperature (25 oC), and time (8.0 min), were used to design a half-factorial, 5-level central composite design. The removal efficacy was observed to be 97.59%. Adsorption equilibrium was studied by various isotherm models, including Freundlich, Langmuir, Temkin, and Dubinin-Radushkevich (D-R), at temperatures ranging from 303 to 323 K. It was observed that the Langmuir model is well, with a maximum CR adsorption capacity of 55.19mg/g and a R2 value of 0.900. The kinetic study followed pseudo-first-order kinetics. It demonstrated that the sorption process followed the pseudo-first-order kinetics. A thermodynamic study was also performed. The recycling and regeneration of adsorbent was also carried out. Desorption experiments were also performed, and maximum desorption capacity was observed in the basic medium, and NaOH showed maximum desorption efficacy. Salt effects, including the matrix effect, were also observed, and maximum adsorption capacity was observed in the presence of a NaCl matrix. Conclusively, this study's results showed that the synthesized nanocomposite is efficacious for dye removal and might prove to be an efficient and eco-friendly method for dye treatment processes.

The use of chitosan as an adsorbent for the removal of oil from oil-in-water emulsion has been investigated in this study. Chitosan is a promising material with various applications in adsorption and is effective in removing several types of pollutants, including vegetable oil. As oil pollution continues to cause significant harm to the environment, adsorption has emerged as a viable method for remediation, and this study seeks to explore its potential in removing oil from wastewater. A series of adsorption experiments were conducted on artificially made oil-in-water emulsions, using chitosan flakes as the adsorbent and cooking vegetable oil as the adsorbate. The study investigated various parameters affecting the sorption capacity, including pH, contact time, oil concentration, adsorbent dose, agitation speed, and temperature. Untreated and unmodified chitosan flakes were used as adsorbents, and the results showed that oil removal efficiencies of up to 80-90% could be achieved by varying individual parameters. Significantly, the peak values were observed individually at 50°C, 30 min of contact time, 0.005 g of adsorbent per 100 mL of emulsion, 0.8% of initial oil concentration, 150 RPM of agitation speed, and a solution pH of 6.02. The potential for improving oil removal with modified chitosan was also discussed, along with an analysis of parameter interaction. The findings suggest that chitosan has significant potential as an adsorbent for oil removal from wastewater and that further research into modifications and optimization of parameters could lead to even greater efficiency in oil removal. Overall, this study contributes to the growing body of research on environmentally friendly and sustainable methods for the bioremediation of oil pollution.

Currently, wastewater treatment is an industrial opportunity to rejuvenate freshwater resources. It is highly needed in water-stressed countries. This work presents a one-step microwave-assisted hydrothermal method for making Ag-TiO2/SBA-15 nanophotocatalysts. XRD, N2 adsorption-desorption isotherms-desorption isotherms, AFM, UV-Vis, and UV-DRS analyses were carried out to characterize the obtained photocatalyst sample. With high Ag loading on the surface of TiO2 nanoparticles, agglomeration of silver nanoparticles and also clogging occurring in the SBA-15 pores are confirmed by AFM analysis. The optical bandgap energies obtained by DRS analysis were significantly blue-shifted, which is the quantization effects improving photocatalytic activities under visible light illumination due to the presence of silver nanoparticles that act as photosensitizer and reduce the recombination of the formed charge carriers (e and hole). Photocatalytic performances of Ag-TiO2/SBA-15 nanophotocatalyst were evaluated by methyl orange (MO) dye photodegradation at different Ag/TiO2 ratios. In MO destruction experiments, the highest photocatalytic efficiency was obtained in the Ag/TiO2-SBA-15 (Ag: TiO2=1.0) photocatalyst at 76.0% and all efficiencies over the synthesized nano photocatalysts are higher than commercial bulk TiO2 nano photocatalyst activity due to the low UV part of the applied visible light halogen lamp and also Ag/TiO2 nano photocatalyst that maybe due to the poor dispersion of active phases. The Ag-TiO2/SBA-15 (1.0) had the highest photocatalytic efficiency at pH=4. The photocatalyst can be reused six times without losing its effectiveness. This shows that the photocatalyst is stable and can be used repeatedly.

Photo-electro-catalysis process has received major attention in the past decade as a substitutional wastewater treatment technology. Photo-electro-catalysis process is widely employed for removing different pollutants (organic, and inorganic (cationic and anionic)) from wastewater. It has been recently developed by modifying the photo-reactor system, the experimental parameters, and the structure of photo-anodes during preparation to enhance the pollutants removal from wastewater, reduce their adverse health risk resulting from environmental accumulation, and give a chance to reuse the treated wastewater for a variety of applications. This review aims to summarize recent studies (especially in the last five years) that developed the photo-electro-catalytic degradation system of organic, heavy metal, and mixed pollutants under UV light, visible light, and sunlight. This review demonstrates the effect of experimental variables, photo-reactor arrangements, mass transfer, phase, length, and diameter of nanoparticles or tubes on the anode, type of deposition on the anode, and cathode characteristics (type and dimensions) on the photo-electro-catalytic technologies. The drawbacks of photo-catalysts, affecting the photo-electro-catalytic properties, are also discussed and solved. Finally, the review focuses on the photo-electro-catalysis enhancements by combining this process with other proven treatment processes. This review can provide perspectives on the important factors that evolve photo-electro-catalysis for the complete purification of polluted wastewater in the future.

In the present study, NiO-MgO nanocomposite was synthesized by the Sol-gel process. Activated carbon was incorporated with the nanocomposite to yield activated carbon coupled Bimetallic Nanocomposites NiO-MgO-AC. The nanocomposite was utilized in an ultrasonic adsorption process to remove Methylene Blue (MB) dye from the simulated Dye effluent. FT-IR, EDS, and SEM were used to determine the chemical composition and structural morphology. The surface neutrality was calculated using PHPZ C, which was found to be 5.5. The experiments were carried out using a four-factorial central composite design with variables such as sonication time, MB dye concentration, pH, and adsorbent dose. To find Optimal Operating Parameters (OOP), the Response Surface Methodology (RSM) was employed. At a pH of 5.0, sonication time of 6.23 minutes, 0.02 g of the nanocomposite, and 10 mg/L concentration of MB dye. The removal efficacy was found to be 93.983%. Various isotherm models, including Freundlich, Langmuir, Temkin, and Dubinin Radushkevichat 303-313K temperatures, were used to study the adsorption equilibrium. The RL values were less than one, suggesting that the adsorption technique was suitable. Furthermore, the values of n were found to be larger than one, indicating that the Freundlich adsorption model was appropriate. The D-R isotherm provides values of E that were seen to be below 8.0kJ/mole at all temperatures indicating a physisorption process.  The thermodynamics of dye removal were also studied in order to obtain the system's DHo, DSo, and DGo values. The pseudo-first and pseudo-second-order, intraparticle diffusion, Elovich, and Boyd kinetic models were used to determine the kinetics of adsorption. The current study's findings indicated that nanocomposites can be efficiently utilized in waste treatment operations. The simulated dye wastewater treatment system was designed locally and can be efficiently employed on a commercial scale for the treatment of effluent before discharge into main streams to minimize its toxicity to the ecosystem.

Effluent, containing toxic and hazardous wastes, discharged by industries has been an eye-catching issue for researchers over the past few years. Mainly, this hazardous waste incorporates a large variety of dyes, chemicals, and traces of heavy metals. This work focuses on the treatment of industrial wastewater using the adsorption technique for Graphite Intercalation Compound (GIC) as an adsorbent. NyexTM 1000, a commercial adsorbent with a surface area of 1.0 m2/g, offering a Bulk density of 0.88 g/cm3 and Pore diameter of 133 Å respectively, was utilized to remediate an industrial contaminant. A GIC adsorbent was found to reduce COD by about 90% i.e., 150 mg/L to 10 mg/L. The outcome of this research has revealed that Graphite intercalation compound (GIC) as an adsorbent is suitable for the reduction of COD from industrial effluent. Kinetic studies reveal adsorbent surface heterogeneity is increased and multilayer adsorption was observed. 6 cyclic adsorption studies were performed by regenerating the adsorbent 5 times consecutively. The GIC adsorbent was regenerated via an electrochemical reactor and has shown a significant regeneration efficiency of more than 99%. The electrochemical reactor was integrated with a solar energy system to make the process cost-effective.

Ever-increasing environmental pollutions and water scarcity are highly challenging issues that pose formidable obstacles to human beings on all fronts. Hetero-photocatalytic methods which utilized semiconductors as photocatalysts are highly promising and green technologies for the degradation of recalcitrant organic pollutants which cannot be completely removed by conventional treatment processes. In the view of the current scenario, zinc oxide nanostructures have been demonstrated to be predominant photocatalyst candidates for photodegradation because of their cost-effectiveness, non-toxicity, strong oxidation capability, flexibility in synthesizing, earth-abundance nature, easy crystallization, and high performance in the absorption over an extensive fraction of solar spectrum in comparison with titanium dioxide. Nevertheless, bare zinc oxide possesses several intrinsic limitations, like high recombination rate of the photogenerated charge carriers, limited solar light application, photo corrosion, broad bandgap and limited visible light absorption. Moreover, photocatalysts separation from remediated solutions restricts their large-scale applications. In this review paper, the authors briefly discussed basic principles of the zinc oxide photocatalytic process besides various modifications such as coupling with low bandgap semiconductors like metal and non-metal doping, synthesizing with graphene oxide, or reduced graphene oxide and their integration in magnetic materials to successfully addressing aforesaid disconcerting challenges. Moreover, hybridized photocatalytic and membrane systems are explored. Finally, challenges and future research directions are proposed for giving profound and well-defined insights toward reaching fully exploited zinc oxide-based nanoparticles in the field of water and wastewater treatments.

Dyes are extensively used across a variety of industries, raising concerns about their potential to contaminate water sources. Therefore, effective and environment-friendly removal techniques are essential. The potential of MXenes as adsorbents for dye adsorption from water is thoroughly examined in this review. Two-dimensional transition metal carbides or nitrides, known as MXenes, have extraordinary physicochemical characteristics, such as a large surface area, variable surface chemistry, and superior adsorption capability. This study examined the structural properties of MXenes, their methods of production, and their special adsorption processes for dye removal. In addition, a thorough analysis of the effects of several variables, including the pH, contact time, initial dye concentration, and temperature, on the adsorption efficiency of MXenes was performed. This article also highlights the current developments in the MXenes modification to increase the effectiveness of their dye adsorption. Furthermore, this report addresses the difficulties in applying MXenes as adsorbents in practice and suggests future research avenues to overcome these restrictions. Overall, this study offers insights into the prospective use of MXenes in water treatment technologies and portrays them as promising and long-lasting adsorbents for the removal of synthetic dyes from water.

In the present work, a polyacrylamide-pumice stone (PAAm-PMC) composite has been synthesized and used as an adsorbent for the fast removal of copper ions from wastewater. The PAAm-PMC composite was synthesized by the conventional free radical polymerization method and characterization has been done by Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscope (SEM). Effects of various parameters on the adsorption capacity of the synthesized PAAm-PMC composite were studied and optimized. The optimized values of various parameters found were: contact time (60 minutes), pH value of solution (6.5), composite dose (0.05 g), Cu(II) concentration (1500 mg/L), and temperature (323 K). The kinetic studies reveal that the rate of adsorption of copper on the composite, increases with time and the maximum adsorption achieved for copper ions is ~ 96 %. The fast adsorption kinetics followed pseudo-second-order kinetics when modified composites were used. Among three different isotherm models, Langmuir adsorption isotherm model has been found to be the best-correlated model with experimental data based on a higher correlation coefficient with a maximum Langmuir loading of 500 mg/g. The positive entropy during the adsorption process for both the materials (ΔS0= (55.6855 J/(mol.K) for PAAm and 151.0737 J/(mol.K) for PAAm-PMC at 303K) suggests, that the adsorption process is thermodynamically favorable and increases with the increase in temperature. Gibbs free energy values are found to be higher for composite material suggesting higher equilibrium constant values (ΔG0 = -5.0191 kJ/mol for PAAm vs -8.0059 KJ/mol PAAm-PMC at 303K). Structural strength and stability of the synthesized composite can be accessed, as modified composites were used up to three times for the adsorption removal of Cu(II) ions from waste-water, after regeneration. These investigations confirmed that the synthesized PAAm-PMC composite can work as an effective adsorbent for the economical and fast removal of Cu(II) ions from wastewater.

Organophosphorus compounds such as diethyl dithiophosphate (DEDTP) are extremely toxic and cause significant environmental and water contaminations in nature. To mitigate its hazardous influence on the wastewater treatment processes, the present study was implemented focusing on the operating variable of the ion flotation technique. The effects of different parameters including initial pH (4-10), impeller speed (700-1000 rpm), and conditioning time (2-4 min) were investigated to maximize DEDTP removal from synthetic wastewater with an initial amount of 58 ppm. The N-Cetyl-N,N,N-trimethyl-ammonium bromide (CTAB) was used as the collector and frother in the ion flotation tests. The experimental results were analyzed based on the foamability, foam stability, and turbidity. The ion flotation experimental results showed that the DEDTP could be removed with the percentage removal of 91 under the optimum operating conditions of pH=10, collector dosage 1.09 ´ 10-3 M, impeller speed 850 rpm, and conditioning time with the collector for 3 min. It was observed that the percentage removal of DEDTP was dependent on the foam properties and electrostatic interactions between CTAB and DEDTP. The turbidity studies proved that DEDTP formed 1:2 complexes with CTAB at pH 10.

In this study, eco-friendly composite material polyacrylamide/cellulose hydrogel reinforced with fuller’s earth (PAAm/CG/FE), has been synthesized and used for the effective adsorption of the Methylene Blue (MB) dye. The synthesis of PAA/CG/FE composite followed the free radical polymerization method. Chemical compositions and morphology of the synthesized composite have been characterized by Fourier Transform InfraRed (FT-IR) Spectroscopy and Scanning Electron Microscope (SEM). Thermal stability has been determined by TGA analysis. Batch adsorption experiments have been carried out by varying different parameters viz. contact time, pH of the solution, and temperature in order to determine the maximum dye adsorption capacity of the composite. Introducing cellulose and fuller earth into the polyacrylamide eventually enhanced the structural stability, thermal stability, and MB adsorption capacity. Based on the experimental data, adsorption kinetics has been found to be well correlated with the pseudo-second-order kinetic model. It has been found that the equilibrium adsorption isotherm data perfectly followed the Langmuir isotherm model and maximum adsorption capacities were found to be 48.30 and 56.17 mg/g for PAAm and PAAm/CG/FE composite, respectively. Furthermore, the prepared composite exhibits good reusability, and it is economic, eco-friendly, and nontoxic material.

The effect of pH and the amount of Ca(OH)2 on the precipitation of boron from Eti Maden Kırka Boron Operations’ wastewater that contained 2752 ppm boron was investigated. It was observed that control of pH was the most important parameter and stepwise addition of Ca(OH)2 after adjustment of pH improved the precipitation. The best result was obtained in the two-stage addition of Ca(OH)2 with the initial control of pH and additional use of aluminum sulfate in the second stage which helped both in the reduction of pH and coagulation. Under these conditions, it was possible to lower the boron content in the wastewater to 250 ppm.

Vinasse is a well-known associate of sugar cane/beet ethanol production wastewater. In the present work, the electrocoagulation technique at a constant current intensity combined with circulation flow introduces as a new and economic method for the treatment of vinasse effluent using iron and/or aluminum without changing the initial conditions of sample solution. Spectrophotometric determination was used to quantify the COD and turbidity in effluents as the most regarded vinasse footprints. The proposed CCD method was used as an experimental design, having as independent variables, applied current, pH, electrode material, and the reaction time, evaluated for highest COD, turbidity, and color removal. The optimum conditions for removal of COD, color and turbidity determined by response surface modeling (RSM) showed that the proposed circulating electrocoagulation (CEC) method using aluminum-graphite electrodes at 1 A current, pH 7 and reaction time of 45 min is able to be used with high efficiency for the treatment of vinasse wastewater in ethanol production industry. The proposed method is very simple, cheap and fast and can be used as a pilot system in alcohol factories to recover the water which can, in turn, be utilized for agricultural purposes and other industries.