Catalytic ozonation of textile wastewater as a polishing step after industrial scale electrocoagulation

Advancements in combined electrocoagulation processes for sustainable wastewater treatment: A comprehensive review of mechanisms, performance, and emerging applications

This review explores the potential and challenges of combining electrochemical, especially electrocoagulation (EC) process, with various - wastewater treatment methods such as membranes, chemical treatments, biological methods, and oxidation processes to enhance pollutant removal and reduce costs. It emphasizes the advantages of using electrochemical processes as a pretreatment step, including increased volume and improved quality of permeate water, mitigation of membrane fouling, and lower environmental impact. Pilot-scale studies are discussed to validate the effectiveness of combined EC processes, particularly for industrial wastewater. Factors such as electrode materials, coating materials, and the integration of a third process are discussed as potential avenues for improving the environmental sustainability and cost-effectiveness of the combined EC processes. This review also discusses factors for improvement and explores the EC process combined with Advanced Oxidation Processes (AOP). The conclusion highlights the need for combined EC processes, which include reducing electrode consumption, evaluating energy efficiency, and conducting pilot-scale investigations under continuous flow conditions. Furthermore, it emphasizes future research on electrode materials and technology commercialization. Overall, this review underscores the importance of combined EC processes in meeting the demand for clean water resources and emphasizes the need for further optimization and implementation in industrial applications.

Electrocoagulation using Ti/Ti for the remediation and reuse of aqueous Dispersive Blue-79

The entire ecology is contaminated by the synthetic dyes that are widely utilised in the textile industries. They can be handled using a variety of technologies, but an eco-friendly method called electrocoagulation has been used to prevent additional contamination. Textile wastewater containing disperse dyes are successfully treated in Electrocoagulation (EC) utilizing Al, Fe, and Stainless Steel (SS), but it is not cost effective, also the treated water contains certain mg/L of the metals used, along with dye components, which obstructs the reuse of the same. The effects of initial pH, applied voltage, dye concentration, supporting electrolyte, and treatment time on the colour removal efficiency (CRE) and consumption of energy were examined in EC process followed by activated charcoal filtration (hybrid process) with a monopolar Ti/Ti electrode on the remediation of aqueous solution of Dispersive Blue-79 (dye 3G). The maximum CREobtained was 99.4%, chemical oxygen demand (COD) 93%, and biological oxygen demand (BOD) 85%, under the following optimized operating conditions, applied voltage 15 V, pH = 7, concentration of dye, electrolyte 110 mg/L, 0.2 g/L and time = 15 min. The overall operating cost for the treatment of aqueous dye 3G was 0.455US/m3. The mechanism of EC was studied using XPS analysis in the sludge obtained. For the purpose of the reuse, FTIR, AAS, and ICP-OES analysis were done and compared with the aqueous dye 3G, after EC and hybrid process to ensure the maximum removal of the degraded dye components and metal. ICP-OES results showed that there were no traces of metal in the treated aqueous dye 3G using this method. Throughout the study, the experimental outcomes indicated that the hybrid process upgraded the quality of the treated aqueous dye 3G.

Electrochemical-based approaches for the treatment of pharmaceuticals and personal care products in wastewater

In recent times, emerging contaminants (ECs) like pharmaceuticals and personal care products (PPCPs) in water and wastewater have become a major concern in the environment. Electrochemical treatment technologies proved to be more efficient to degrade or remove PPCPs present in the wastewater. Electrochemical treatment technologies have been the subject of intense research for the past few years. Attention has been given to electro-oxidation and electro-coagulation by industries and researchers, indicating their potential to remediate PPCPs and mineralization of organic and inorganic contaminants present in wastewater. However, difficulties arise in the successful operation of scaled-up systems. Hence, researchers have identified the need to integrate electrochemical technology with other treatment technologies, particularly advanced oxidation processes (AOPs). Integration of technologies addresses the limitation of indiviual technologies. The major drawbacks like formation of undesired or toxic intermediates, s, energy expenses, and process efficacy influenced by the type of wastewater etc., can be reduced in the combined processes. The review discusses the integration of electrochemical technology with various AOPs, like photo-Fenton, ozonation, UV/H2O2, O3/UV/H2O2, etc., as an efficient way to generate powerful radicals and augment the degradation of organic and inorganic pollutants. The processes are targeted for PPCPs such as ibuprofen, paracetamol, polyparaben and carbamezapine. The discussion concerns itself with the various advantages/disadvantages, reaction mechanisms, factors involved, and cost estimation of the individual and integrated technologies. The synergistic effect of the integrated technology is discussed in detail and remarks concerning the prospects subject to the investigation are also stated.

Natural-based coagulants/flocculants as sustainable market-valued products for industrial wastewater treatment: a review of recent developments

Industrial wastewater is categorized as a voracious consumer of fresh water and a high-strength source of pollution. Coagulation-flocculation is a simple and cost-effective technique for removing organic/inorganic compounds and colloidal particles from industrial effluents. Despite the outstanding natural properties, biodegradability, and efficacy of natural coagulants/flocculants (NC/Fs) in industrial wastewater treatment, their significant potential to remediate such effluents is underappreciated, particularly in commercial scale applications. Most reviews on NC/Fs focused on the possible application of plant-based sources such as plant seeds, tannin, certain vegetables/fruit peels, and their lab-scale potential. Our review expands the scope by examining the feasibility of using natural materials from other sources for industrial effluent decontamination. By analyzing the latest data on NC/Fs, we identify the most promising preparation techniques for making these materials stable enough to compete with traditional options in the marketplace. An interesting presentation of the results of various recent studies has also been highlighted and discussed. Additionally, we highlight the recent success of using magnetic-natural coagulants/flocculants (M-NC/Fs) in treating diverse industrial effluents, and discuss the potential for reprocessing spent materials as a renewable resource. The review also offers different concepts for suggested large-scale treatment systems used by MN-CFs.

Efficient removal of norfloxacin from water using batch airlift-electrocoagulation reactor: optimization and mechanisms analysis

In this study, we developed an airlift-electrocoagulation (AL-EC) reactor to remove norfloxacin (NOR) from water. Six parameters influencing NOR removal were investigated, and the possible removal mechanism was proposed based on flocs characterization and intermediates analysis. The performances for treating different antibiotics and removing NOR from 3 types of water were also evaluated. The best NOR removal efficiency was obtained with the iron anode and aluminum cathode combination, a current density of 2 mA cm-2, an initial pH of 7, a treatment time of 32 minutes and an air flow rate of 200 mL min-1, the supporting electrolyte type was NaCl, and the initial NOR concentration was 10 mg L-1. Flocs adsorption and electrochemical oxidation were the main ways to remove NOR from water. The average removal efficiency of the AL-EC reactor exceeded 60% of the different antibiotic concentrations in artificial and real water. The highest NOR removal rate reached 93.48% with an operating cost of 0.153 USD m-3. The present work offers a strategy for NOR removal from water with high efficiency and low cost, showing a huge potential for the application of the AL-EC in antibiotic contaminated water treatment.

Low-pressure thin-film composite nanofiltration membranes with enhanced selectivity and antifouling property for effective dye/salt separation

For better sustainable resource recovery and elevating the separation efficiency of dye/salt mixture, it is essential to develop an appropriate nanofiltration membrane for the treatment of textile dyeing wastewater containing relatively smaller molecule dyes. In this work, a novel composite polyamide-polyester nanofiltration membrane was fabricated by tailoring amino functionalized quantum dots (NGQDs) and β-cyclodextrin (CD). An in-situ interfacial polymerization occurred between the synthesized NGQDs-CD and trimesoyl chloride (TMC) on the modified multi-carbon nanotubes (MWCNTs) substrate. The incorporation of NGQDs significantly elevated the rejection (increased by ∼ 45.08%) of the resultant membrane for small molecular dye (Methyl orange, MO) compared to the pristine CD membrane at low pressure (1.5 bar). The newly developed NGQDs-CD-MWCNTs membrane exhibited enhanced water permeability without compromising the dye rejection compared to the pure NGQDs membrane. The improved performance of the membrane was primarily attributed to the synergistic effect of functionalized NGQDs and the special hollow-bowl structure of CD. The optimal NGQDs-CD-MWCNTs-5 membrane expressed pure water permeability of 12.35 L m^-2h^-1 bar^-1 at the pressure of 1.5 bar. Noteworthily, the NGQDs-CD-MWCNTs-5 membrane not only showed high rejection for the larger molecular dye of Congo Red (CR, 99.50%) but also for the smaller molecular dye of MO (96.01%) and Brilliant Green (BG, 95.60%) with the permeability of 8.81, 11.40, and 6.37 L m^-2h^-1 bar^-1, respectively at low pressure (1.5 bar). The rejection of inorganic salts by the NGQDs-CD-MWCNTs-5 membrane was 17.20% for sodium chloride (NaCl), 14.30% for magnesium chloride (MgCl₂), 24.63% for magnesium sulfate (MgSO₄), and 54.58% for sodium sulfate (Na₂SO₄), respectively. The great rejection of dyes remained in the dye/salt binary mixed system (higher than 99% for BG and CR, <21% for NaCl). Importantly, the NGQDs-CD-MWCNTs-5 membrane exhibited favorable antifouling performance and potential good operation stability performance. Consequently, the fabricated NGQDs-CD-MWCNTs-5 membrane suggested a prospective application for the reuse of salts and water in textile wastewater treatment owing to the effective selective separation performance.

Electro-Fenton mineralization of real textile wastewater by micron-sized ZVI powder anode

The diverse compositions and complex nature of the textile wastewater make it imperative to find an economical and suitable degradation pathway. The degradation of real textile wastewater on a novel heterogeneous electro-Fenton system was carried out with a composite anode of magnetically fixed micron ZVI coupling with a Ti/RuO₂-IrO₂ sheet. The influences of different variables such as mZVI dosage, H₂O₂ amount, applied voltage and pH value on both total organic carbon and chemical oxygen demand removal efficiencies and energy consumption were investigated. The optimized parameters were simultaneously verified by using electrochemical workstation Tafel curves and Nyquist plots. The optimal operating conditions for evaluating the wastewater treatment were H₂O₂ dosage of 0.10 mol·L^-1, applied voltage of 5.0 V, mZVI amount of 1.0 g·L^-1 and initial pH value of 3.0. The high TOC and COD removal efficiencies of 92.44 and 82.84% could be achieved simultaneously in 60 min, respectively. XRD, XPS and SEM-EDS were used to investigate the interaction between the pollutant and the mZVI. GC-MS analysis was performed on untreated and treated wastewater to determine the degradation of pollutants in dyeing wastewater during the electro-Fenton process and to effectively propose a suitable degradation mechanism for this system.

Efficient removal of dyes from aqueous solutions using short-length bimodal mesoporous carbon adsorbents

Ordered mesoporous carbons (OMCs) with controlled mesopore lengths and volumes were synthesized and investigated to remove the model dye methylene blue (MB) from aqueous solutions. The pore size, specific surface area, pore volume, and pore length of OMCs (CMK-3, sCMK-3, and sCMK-5) were analyzed and benchmarked against commercial activated carbon (AC). CMK-3 and sCMK-3 had narrow pore size distributions (PSDs) centered at ∼4.4 nm, whereas the PSD of sCMK-5 was bimodal, derived from the same pores as CMK-3 (∼4.4 nm) and the inner diameter of the carbon nanotubes (∼5.8 nm). The pore length decreased from 743 nm for CMK-3 to 173 nm for sCMK-3 and 169 nm for sCMK-5, facilitating the MB accessibility and efficient utilization of internal mesopores. The MB adsorption on the prepared adsorbents was well described by a pseudo-second-order kinetic model (R² > 0.999), and the initial adsorption rate (h) on sCMK-5 was 34.07-fold faster than that on commercial AC. The Langmuir model adequately explained the equilibrium adsorption data, and the increase in the Langmuir maximal adsorption capacity (q_m) of the OMCs was proportional to the specific surface area. The MB adsorption on sCMK-5 was endothermic and spontaneous, and proceeded primarily through physical adsorption as well as chemisorption reacting with oxygen atoms in hydroxyl groups. The prepared adsorbents were also suitable for polishing textile wastewater containing color-causing substances along with the background organic matter. These OMCs are promising for treating wastewater as efficient adsorbents for large molecular pollutants such as dyes.

Prediction of pharmaceutical and personal care products elimination during heterogeneous catalytic ozonation via chemical kinetic model

Prediction of the removal of pollutants is important for the process design and optimization of wastewater treatment. In this study, the heterogeneous catalytic ozonation chemical kinetic model based on reaction kinetic constants between O₃ (and •OH) and pollutants, and pseudo-first order rate constants for pollutant adsorption was established. The model parameters were obtained via O₃ and p-chlorobenzonic acid decay curves, and adsorption kinetic experiments, respectively. Higher •OH exposures were obtained at the expense of lower O₃ exposures during catalytic ozonation compared to simple ozonation. Importantly, the experimentally measured and model-predicted removal ratios correlated well in all reaction systems, with correlation coefficients above 0.950 in synthetic solution and 0.893-0.979 in secondary effluent. Furthermore, the model revealed that pollutants were degraded mainly by O₃ and/or •OH oxidation during catalytic ozonation, while adsorption of pollutants on catalysts contributed negligibly. Hence, the degradation ratios of pollutants could be satisfactorily predicted using the simplified model based only on the O₃ and •OH exposures in the heterogeneous catalytic ozonation systems with low adsorption capacity catalysts.

Auramine O UV Photocatalytic Degradation on TiO2 Nanoparticles in a Heterogeneous Aqueous Solution

Amongst the environmental issues throughout the world, organic synthetic dyes continue to be one of the most important subjects in wastewater remediation. In this paper, the photocatalytic degradation of the dimethylmethane fluorescent dye, Auramine O (AO), was investigated in a heterogeneous aqueous solution with 100 nm anatase TiO2 nanoparticles (NPs) under 365 nm light irradiation. The effect of irradiation time was systematically studied, and photolysis and adsorption of AO on TiO2 NPs were also evaluated using the same experimental conditions. The kinetics of AO photocatalytic degradation were pseudo-first order, according to the Langmuir–Hinshelwood model, with a rate constant of 0.048 ± 0.002 min−1. A maximum photocatalytic efficiency, as high as 96.2 ± 0.9%, was achieved from a colloidal mixture of 20 mL (17.78 μmol L−3) AO solution in the presence of 5 mg of TiO2 NPs. The efficiency of AO photocatalysis decreased nonlinearly with the initial concentration and catalyst dosage. Based on the effect of temperature, the activation energy of AO photocatalytic degradation was estimated to be 4.63 kJ mol−1. The effect of pH, additional scavengers, and H2O2 on the photocatalytic degradation of AO was assessed. No photocatalytic degradation products of AO were observed using UV–visible and Fourier transform infrared spectroscopy, confirming that the final products are volatile small molecules.

Fe-zeolite catalyst for ozonation of pulp and paper wastewater for sustainable water resources

The pulp and paper industry consumes enormous quality of freshwater, leading to wastewater. It must be treated to remove pollutants, particularly residual dyestuffs, before releasing them to water bodies to avoid adverse environmental effects. The traditional wastewater treatment methods used for the pulp and paper industry are less efficient in colour and chemical oxygen demand (COD) removal. The current study is aimed at developing a novel catalyst for the catalytic ozonation of pulp and paper wastewater with better colour and COD removal for sustainable resources of clean water. The proposed catalyst is impregnated by iron on natural zeolites. Various parameters such as catalyst dose, pH, ozone dose, initial COD concentration, and reaction time are studied and optimized. The performance was evaluated by comparing the results with the single ozonation process (SOP) and catalytic ozonation process (COP). The highest COD and colour reduction efficiencies have been achieved, i.e., 71%, and 88% at a natural pH of 6.8. The proposed process achieved higher COD and colour efficiencies than the single ozonation process and catalytic ozonation process using raw zeolites. The improvement in efficiencies are 23% and 29% for SOP and 17% and 19% for COP, respectively. Hence, the results proposed the sustainability and applicability of COP to treat paper and pulp sector effluent.

Trimetallic Sulfide Hollow Superstructures with Engineered d-Band Center for Oxygen Reduction to Hydrogen Peroxide in Alkaline Solution

High-performance transition metal chalcogenides (TMCs) as electrocatalysts for two-electron oxygen reduction reaction (2e-ORR) in alkaline medium are promising for hydrogen peroxide (H₂ O₂ ) production, but their synthesis remains challenging. In this work, a titanium-doped zinc-cobalt sulfide hollow superstructure (Ti-ZnCoS HSS) is rationally designed as an efficient electrocatalyst for H₂ O₂ electrosynthesis. Synthesized by using hybrid metal-organic frameworks (MOFs) as precursors after sulfidation treatment, the resultant Ti-ZnCoS HSS exhibits a hollow-on-hollow superstructure with small nanocages assembled around a large cake-like cavity. Both experimental and simulation results demonstrate that the polymetallic composition tailors the d-band center and binding energy with oxygen species. Moreover, the hollow superstructure provides abundant active sites and promotes mass and electron transfer. The synergistic d-band center and superstructure engineering at both atomic and nanoscale levels lead to the remarkable 2e-ORR performance of Ti-ZnCoS HSS with a high selectivity of 98%, activity (potential at 1 mA cm^-2 of 0.774 V vs reversible hydrogen electrode (RHE)), a H₂ O₂ production rate of 675 mmol h^-1 g_cat ^-1 , and long-term stability in alkaline condition, among the best 2e-ORR electrocatalysts reported to date. This strategy paves the way toward the rational design of polymetallic TMCs as advanced 2e-ORR catalysts.

Evaluation of the hybrid system combining electrocoagulation, nanofiltration and reverse osmosis for biologically treated textile effluent: Treatment efficiency and membrane fouling

The efficiency of the hybrid electrocoagulation-nanofiltration-reverse osmosis (EC-NF-RO) system for the treatment of biologically treated textile effluent was investigated. The treatment performances and membrane fouling behaviours of nanofiltration (NF) and hybrid EC-NF systems were compared. EC process was evaluated concerning mitigate the membrane fouling and increasing the removal efficiencies. Besides, the treated wastewater with the hybrid EC-NF process was finally processed using RO process for reuse purpose in the textile industry. The EC treatment was applied using Fe and Al electrodes at various conditions; pH:4-10, current density:0.5-17 mA/cm² and operating time:30-180 min. Fe electrode showed better performance in terms of higher removal efficiencies (76% COD, 96% DFZ₄₃₆), lower energy (21.1 kWh/m³) and electrode consumptions (3.7 kg/m³) for the optimum conditions. Scanning Electron Microscopy-Energy Dispersive Index (ESEM-EDX) and Fourier-Transform Infrared Spectroscopy (FTIR) analyses were carried out for EC sludge samples obtained with Fe and Al electrodes. Desal 5 DL and NF 270 membranes were tested in terms of removal efficiency and membrane fouling for NF and hybrid EC-NF process of textile wastewater. Membrane fouling was evaluated with flux values, resistance-in-series model results as well as Atomic Force Microscopy (AFM), FTIR and contact angle measurements. NF 270 membrane achieved better chloride (28%) and conductivity (41%) removal efficiencies for NF treatment. EC pretreatment did not result in any noticeable improvement in rejections except for chloride (48%) and conductivity (59%) for the hybrid EC-NF process with NF 270. The ratios of R_c decreased to 40% for NF 270 and 42% for Desal 5DL after EC pretreatment. NF270 membrane indicated high permeate flux and low membrane fouling considering cake resistance distribution, surface roughness, hydrophilicity and chemical structure variation. >93% COD, 99% conductivity, 97% chloride, and 91% TDS removal efficiencies were obtained with the hybrid EC-NF-RO process. Finally, the obtained high quality water by RO after the EC + NF 270 hybrid process could be used for all textile finishing process.

Global trends of textile waste research from 2005 to 2020 using bibliometric analysis

Researchers have broadly studied textile waste, but the research topics development and performance trends in this study area are still unclear. A bibliometric analysis was conducted to explore the global scientific literature to determine state of the art on textile waste over the past 16 years. Data of publications output are identified based on the Web of Science (from 2015 to 2020). This study used VOSviewer to analyse collaboration networks among authors, countries, institutions, and author's keywords in identifying five main clusters. A total of 3296 papers in textile waste research were identified. In this study, a total of 10451 authors were involved in textile waste research, and 36 authors among them published more than ten research publications in the period of this study. China has been in a top position in textile waste research moving from 3 output publications in 2005 to 91 output publications in 2020. Indian Institute of Technology System IIT System was ranked first in terms of the total publication number (85 publications, 2.45%). Textile wastewater and adsorption are the most commonly used keywords that reflect the current main research direction in this field and received more attention in recent years. Based on keyword cluster analysis outputs, textile waste research can be categorized into five types of clusters, namely (1) pollutant compositions, (2) component of textile wastewater, (3) treatment methods for textile wastewater, (4) effect mechanism of textile wastewater, and (5) recyclability of textile waste.

A comparative study among catalytic wet air oxidation, Fenton, and Photo-Fenton technologies for the on-site treatment of hospital wastewater

The feasibility of catalytic wet air oxidation, intensified homogeneous Fenton and heterogeneous Photo-Fenton systems for the treatment of real hospital wastewater has been investigated. Wastewater samples were collected from a hospital sewer, during a weekly monitoring program, and fully characterized. Up to seventy-nine pharmaceuticals, including mostly parent compounds and some of their transformation products, were analyzed. Catalytic wet air oxidation allowed the complete removal of several pharmaceutical groups, but it did not allow to eliminate analgesics/anti-inflammatories and antibiotics, whose average removal was around 85%. Intensified Fenton oxidation was the most efficient process for all the drugs removal with an almost complete reduction of the initial pharmaceutical load (99.8%). The heterogeneous Photo-Fenton system reached a 94.5% reduction of the initial pharmaceutical load. The environmental risk of the treated samples by the hazard quotient (HQ) method was also evaluated. Fenton oxidation was the most effective system with a final ∑HQ of 5.4. Catalytic wet air oxidation and Photo-Fenton systems achieved total ∑HQ values of 895 and 88, respectively. This fact was related to the presence of refractory antibiotics in the treated catalytic wet air oxidation samples. On the opposite, the Photo-Fenton system provided the elimination of most pharmaceutical pollutants that pose a high environmental risk such as antibiotics. Simplified cost estimation was finally performed as a preliminary approach of the economy of the three oxidation processes for the hospital wastewater treatment.

Preparation of Pd–Ni Nanoparticles Supported on Activated Carbon for Efficient Removal of Basic Blue 3 from Water

Pd–Ni nanoparticles supported on activated carbon (Pd–Ni/AC) were prepared using a phase transfer method. The purpose of synthesizing ternary composites was to enhance the surface area of synthesized Pd–Ni nanoparticles, as they have a low surface area. The resulting composite was characterized by scanning electronic microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) for investigating its surface morphology, particle size, percentage of crystallinity and elemental composition, respectively. The XRD data and EDX analysis revealed the presence of Pd–Ni alloys impregnated on the AC. Pd–Ni/AC was used as an adsorbent for the removal of the azo dye basic blue 3 from an aqueous medium. Kinetic and isotherm models were used to calculate the adsorption parameters. The most suitable kinetic model amongst the applied models was the pseudo-second-order model, confirming the chemisorption characteristics of the process, and the most suitable isotherm model was the Langmuir model, with a maximum adsorption capacity of 333 mg/g at 333 K. Different experimental parameters, such as the adsorbent dosage, pH, temperature and contact time, were optimized. The optimum parameters reached were: a pH of 12, temperature of 333 K, adsorbent dosage of 0.01 g and optimum contact time of 30 min. Moreover, the thermodynamics parameters of adsorption, such as Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°), showed the adsorption processes being exothermic with values of ΔH° equal to −6.206 kJ/mol and being spontaneous with ΔG° values of −13.297, −13.780 and −14.264 kJ/mol, respectively at 293, 313 and 333 K. An increase in entropy change (ΔS°) with a value of 0.0242 kJ/mol K, indicated the enhanced disorder at a solid–solution interface during the adsorption process. Recycling the adsorbent for six cycles with sodium hydroxide and ethanol showed a decline in the efficiency of the selected azo dye basic blue 3 up to 79%. The prepared ternary composite was found effective in the removal of the selected dye. The removal of other pollutants represents one of the possible future uses of the prepared adsorbent, but further experiments are required.

Recent Achievements in Dyes Removal Focused on Advanced Oxidation Processes Integrated with Biological Methods

In the last 3 years alone, over 10,000 publications have appeared on the topic of dye removal, including over 300 reviews. Thus, the topic is very relevant, although there are few articles on the practical applications on an industrial scale of the results obtained in research laboratories. Therefore, in this review, we focus on advanced oxidation methods integrated with biological methods, widely recognized as highly efficient treatments for recalcitrant wastewater, that have the best chance of industrial application. It is extremely important to know all the phenomena and mechanisms that occur during the process of removing dyestuffs and the products of their degradation from wastewater to prevent their penetration into drinking water sources. Therefore, particular attention is paid to understanding the mechanisms of both chemical and biological degradation of dyes, and the kinetics of these processes, which are important from a design point of view, as well as the performance and implementation of these operations on a larger scale.

Industrial Textile Wastewater Ozone Treatment: Catalyst Selection

One of the recent trends in textile wastewater treatment has become catalytic ozonation. The necessity of effective color removal in a short treatment time is a standard during industrial implementation. At the same time, efficient chemical oxygen demand (COD), total organic carbon (TOC), and toxic by-product removal are highly expected. This study presents the results of a catalytic ozonation treatment. Three types of catalysts: a metal oxide (TiO2 as P25 by Degussa), activated carbon (nano-powder by Sigma, AC), and metal particles (platinum, 1% wt. supported on AC matrix by Sigma, Pt–AC) have been applied. The investigations were conducted for real industrial wastewater originated in textile dyeing with Reactive Black 5 dye (RB5). The experiments ran for the raw wastewater (without pretreatment), exposed blocking of the catalytic action by all used catalysts. The catalytic effect could be observed when catalytic ozonation was used as a polishing step after electrocoagulation (EC). Although the catalytic effect could be observe for all catalysts then, especially in the removal of colorless by-products, the AC was exposed as the most effective. This contributed to 35% and 40% of TOC and COD removal. While only 18% and 23% of TOC and COD were removed in the same process without AC. The decrease in toxicity was 30%. The results of the study revealed the complexity of the issue and resulted in an extensive discussion devoted to the basis of the catalytic activity of each catalyst.