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Abstract This review investigates the pervasive issue of dye effluent pollution in African surface waters, focusing on its significant adverse effects on both human health and environmental quality. Drawing from 63 articles published between 2004 and 2022, the review includes studies from Northern, Western, Eastern, Central, and Southern Africa, illustrating the widespread nature of dye contamination across the continent. Five primary sources of dye effluents are identified: textiles, food industries, dye producers, artisan dyes, and tannery-paint industries, all of which contribute substantially to the degradation of water quality. The physicochemical properties of dye effluents show high toxicity levels in surface waters, with significant regional variations. These variations highlight the importance of considering the specific characteristics of dye types and processing chemicals to fully understand the contamination levels. In evaluating treatment methods, the review finds that adsorption, coagulation/flocculation, filtration, and advanced oxidation processes (AOPs) such as photocatalysis, photo-Fenton oxidation, and plasma-chemical treatment are effective in mitigating dye pollution. The application of these methods varies across different African regions, indicating the need for region-specific approaches based on local conditions and available resources. The review also examines the impact of dye effluents on aquatic ecosystems and human health, with risk assessments revealing effects ranging from acute to chronic. This demonstrates the urgent need for targeted interventions to address dye effluent pollution in African surface waters, thereby protecting both environmental and public health. Graphical Abstract

This review investigates the pervasive issue of dye effluent pollution in African surface waters, focusing on its significant adverse effects on both human health and environmental quality. Drawing from 63 articles published between 2004 and 2022, the review includes studies from Northern, Western, Eastern, Central, and Southern Africa, illustrating the widespread nature of dye contamination across the continent. Five primary sources of dye effluents are identified: textiles, food industries, dye producers, artisan dyes, and tannery-paint industries, all of which contribute substantially to the degradation of water quality. The physicochemical properties of dye effluents show high toxicity levels in surface waters, with significant regional variations. These variations highlight the importance of considering the specific characteristics of dye types and processing chemicals to fully understand the contamination levels. In evaluating treatment methods, the review finds that adsorption, coagulation/flocculation, filtration, and advanced oxidation processes (AOPs) such as photocatalysis, photo-Fenton oxidation, and plasma-chemical treatment are effective in mitigating dye pollution. The application of these methods varies across different African regions, indicating the need for region-specific approaches based on local conditions and available resources. The review also examines the impact of dye effluents on aquatic ecosystems and human health, with risk assessments revealing effects ranging from acute to chronic. This demonstrates the urgent need for targeted interventions to address dye effluent pollution in African surface waters, thereby protecting both environmental and public health. Highlights: Dye effluent pollution severely impacts human health and the environment, particularly in African surface waters. Six key industries contribute to dye pollution in Africa: textile, food, pharmaceutical, tannery, paint, and artisanal. Effective treatment methods like adsorption, filtration, and AOPs show promise but require larger-scale implementation [ABSTRACT FROM AUTHOR]

The present study evaluates the Decolorization and pollutant removal efficiency of chemically impregnated coconut shell-activated carbon using textile dye effluent in the filtration system. The coconut shell zinc chloride activated carbon (CSZAC) was used as a filtering media in wastewater treatment due to its wider pore space with better surface area (590.80 m2 g−1) and higher adsorption capacity. The SEM micrograph revealed that the activated carbon had networks of parallel running pores with internal microstructure and more active sites. The designed activated carbon filter system has dimensions of 90 x 60 x 30 cm; the sections included are the holding tank (50 liters capacity), filtration tank and storage tank with the optimized flow rate of 5 x 10−4 m3 min−1. The Color, pH, EC, TDS, TSS, BOD and COD of textile dyeing wastewater were significantly reduced, after the treatment through the CSZAC filtration system. The initial color concentration of textile dye effluent was 7021 HU and after treatment, the color was fully reduced and became colorless. CSZAC treatment reduced the BOD from 600 mg L−1 to 89.7 mg L−1 (80.6 per cent) and COD from 2500 mg L−1 to 205 mg L−1 (90.5 per cent). Therefore, CSZAC can be used as an effective adsorbent material to remove different dye compounds and pollutants from textile wastewater. [ABSTRACT FROM AUTHOR]

This study aimed to analyze the feasibility of removing Alizarin red S (ARS) used as model pollutant from aqueous solutions using the preparative porous silica composites (PSCs) as adsorbents which were prepared via hydrothermal approach. The physicochemical properties of materials were characterized by means of Transmission electron microscope (TEM), Scanning electron microscope (SEM), Energy dispersive spectrometer (EDS), Brunauer-Emmett-Teller (BET) method, Barret-Joyner-Halenda (BJH) method, Fourier Transform Infrared Spectrometer (FTIR) and X-Ray Diffractometer (XRD). PSCs possessed the specific surface area were 731.6 m2/g, 420.9 m2/g, 294.6 m2/g, respectively. The presence of silica structures was confirmed by FTIR spectra. In order to confirm efficiency of composites as adsorbents and reveal adsorption mechanism, the impacts of pH, contact time, initial ARS concentration, temperature on adsorption were conducted. The adsorption experiment results showed that the adsorption efficiency of ARS onto PSC-3 was better than that of PSC-1 and PSC-2 at pH = 11. Furthermore, the adsorption kinetic models, isotherm models and thermodynamic model were analyzed for comprehensive adsorption process. The maximum adsorption capacity of PSC-3 for ARS was 43.1 mg/g. The pseudo-second-order kinetic model and Sips isotherm model were more suitable for experimental results. The adsorption process was endothermic according to the adsorption thermodynamic model. The free energy of adsorption required for ARS onto PSCs was less than 8 kJ/mol, indicating physical adsorption. What's more, PSC-3 possessed advantages of higher adsorption capacity and shorter equilibration time. Overall, these results made it potentially applicable as an effective adsorbent for ARS dye from effluent. [ABSTRACT FROM AUTHOR]

Organic dyes are extensively used in textile and batik industry. Dispose of untreated dye effluent into water system is hazardous to human and environment. Advanced oxidation process (AOPs) based on heterogeneous TiO2 photocatalyst is proven for effluent treatment. Immobilization of TiO2 photocatalyst on supporting substrate is one of the research focuses to realize its application in industry to minimize the loss of TiO2 photocatalyst over time during effluent treatment. Many synthesis techniques have been used to grow TiO2 photocatalyst on supporting substrates. However, these synthesis techniques are either timeor cost-consuming. In this work, a novel direct heating (DH) technique has been developed for the first time to deposit TiO2 particles on kanthal coils. The optimum deposition of TiO2 particles was achieved in 15 min using 60 W. The TiO2 particles contained mixture of anatase (82.7%) and brookite (17.3%), with an average particle size of 167.36±15.37 nm. The surface coverage of TiO2 particles on kanthal wire was good, with minimum agglomeration. The TiO2 particles deposited on kanthal coils recorded 43.7% of photodegradation efficiency in methylene blue removal under UV light. [ABSTRACT FROM AUTHOR]

Textile and cosmetic industries generate large amounts of dye effluents requiring treatment before discharge. This wastewater contains high levels of reactive dyes, low to none-biodegradable materials and chemical residues. Technically, dye wastewater is characterised by high chemical and biological oxygen demand. Biological, physical and pressure-driven membrane processes have been extensively used in textile wastewater treatment plants. However, these technologies are characterised by process complexity and are often costly. Also, process efficiency is not achieved in cost-effective biochemical and physical treatment processes. Membrane distillation (MD) emerged as a promising technology harnessing challenges faced by pressure-driven membrane processes. To ensure high cost-effectiveness, the MD can be operated by solar energy or low-grade waste heat. Herein, the MD purification of dye wastewater is comprehensively and yet concisely discussed. This involved research advancement in MD processes towards removal of dyes from industrial effluents. Also, challenges faced by this process with a specific focus on fouling are reviewed. Current literature mainly tested MD setups in the laboratory scale suggesting a deep need of further optimization of membrane and module designs in near future, especially for textile wastewater treatment. There is a need to deliver customized high-porosity hydrophobic membrane design with the appropriate thickness and module configuration to reduce concentration and temperature polarization (CP and TP). Also, energy loss should be minimized while increasing dye rejection and permeate flux. Although laboratory experiments remain pivotal in optimizing the MD process for treating dye wastewater, the nature of their time intensity poses a challenge. Given the multitude of parameters involved in MD process optimization, artificial intelligence (AI) methodologies present a promising avenue for assistance. Thus, AI-driven algorithms have the potential to enhance overall process efficiency, cutting down on time, fine-tuning parameters, and driving cost reductions. However, achieving an optimal balance between efficiency enhancements and financial outlays is a complex process. Finally, this paper suggests a research direction for the development of effective synthetic and natural dye removal from industrially discharged wastewater. [Display omitted] • Discharge of dye effluent requires robust and cost-effective treatment processes. • Membrane distillation emerged as a promising tool towards dye remediation. • The current study reviewed research advancement towards environmental dye remediation. • However, fouling and thermal efficiency of MD remain a major challenge. • The reviewed study suggested optimization of membrane and module designs for effective dye remediation. [ABSTRACT FROM AUTHOR]

Endophytic microflora is a lesser approached source for nanoparticles synthesis. Myco-synthesis of iron nanoparticles was carried out using an endophytic fungi Penicillium oxalicum isolated from Tecomella undulata. Synthesized iron nanoparticles were characterized using different techniques. The UV–Visible absorption spectrum showed an absorption band at 300 ​nm, which is a characteristic of iron nanoparticles. The FTIR spectrum of iron nanoparticles showed absorption peaks ranging between 3430.70 cm−1–466.83 cm−1 range. SEM images showed 140 ​nm particles of spherical shape. AFM images indicated particle width and height being 3.9 ​nm and 100 ​nm respectively. The iron nanoparticles formed were used to study decolorization of methylene blue dye in the presence of H2O2. The dye was effectively decolourized up to 99.17% in a time interval of 6 ​h. Myco-synthesized nanoparticle mediated decolorization process confers a possibility of removal of toxic textile effluents in a sustainable way.

Among the industrial chemical wastes, the effluents of loom-dyeing industry raise great concern in recent times because of their diverse environmental hazards. A laboratory experiment was conducted to determine the phytotoxic effect of different loom-dye effluents on seed germination and early seedling growth of red amaranth (Amaranthus tricolor L.) in the Department of Agricultural Chemistry of Bangladesh Agricultural University, Mymensingh, during May to August, 2017. Results revealed that the physico-chemical parameters of loom-dye effluent such as pH, electrical conductivity (EC), total dissolved solids (TDS), sulphate, phosphate, sodium, potassium, iron, manganese and lead concentrations were relatively higher than the suggested range. On the other hand, the concentrations of calcium, zinc, copper and cadmium were relatively lower. Germination experiment of red amaranth were done in sterilized petridishes containing 0, 5, 10, 25, 50, 75 and 100% concentrations of three different types of untreated loom-dyeing effluents following completely randomized design. Three replications were used for each treatment. The germination energy and capacity, growth parameters like root and shoot length, relative toxicity, seedling vigour and phytotoxicity on seed germination of red amaranth in response to different loom-dyeing effluents at various concentrations were also calculated. There was a gradual lessening in the percentage of seed germination and seedling growth with increased concentration of effluents. Relative toxicity and phytotoxicity was extreme at 100% effluent concentration. Different growth parameters such as root and shoot lengths of seedlings was minimum at 100% and maximum at 5% dye effluent concentration. Overall results indicate that pink dye effluent was less toxic to the germination and early growth of red amaranth than violet and black dyes. For most of the growth parameters of red amaranth, the order of phytotoxicity among the loom-dye effluent was black > violet > pink. [Fundam Appl Agric 2018; 3(2.000): 480-490]

Loom-dye effluent discharge has constituted a major environmental threat to the people of Belkuchi Upazila of Sirajganj District. The present study was conducted to characterize loom-dye effluents and investigate their health implications by the growth analysis of rice and red amaranth seedlings along with a survey study among the individuals associated with loom-dyeing, weaving, and crop farming activities. A total of twenty-eight loom-dye effluent samples were collected for physicochemical characterization; among them, only three loom-dye effluents, i.e. pink, violet, and black dyes, at concentrations of 0, 10, 25, 50, 75, and 100% were applied as irrigation water to rice and red amaranth. The plant growth experiment was laid out following a completely randomized design with three replicas. Chemical analyses of loom-dye effluents showed the presence of a significant amount of plant nutrients and heavy metals. The mean concentrations of Pb, Cd, Cr, Fe, Mn, Zn, and Cu were 0.938, 0.046, 0.212, 7.109, 0.609, 0.351, and 0.191 mg L−1, respectively. Among the metals, the concentrations of Pb, Cr, Fe, and Mn were above the recommended limit proposed by the irrigation water guideline value. Application of ≤ 25% pink and violet dye effluent and ≤ 10% black dye effluent had significant (p < 0.05) and positive impacts on growth and yield parameters. Heavy metal content in seedlings increased with increasing effluent application rate and crossed the utmost permissible limit at higher concentration. Survey data discovered a moderate knowledge level among the respondents, which might account for the indiscriminate discharge of loom-dye effluent into the surrounding environment. Attitudes, practices, and protective behaviours of the respondents also reflect the caused for long-term pollution through loom-dye effluents. To reduce its negative effects on the health and crop environment, the loom-dye effluents should not be discharged indiscriminately and used for crop irrigation without proper treatment. Furthermore, training programs ought to be introduced to educate the individuals involved in the discharge and subsequent use of loom-dye effluents. [ABSTRACT FROM AUTHOR]

Biological macromolecule namely cellulose nanofiber was synthesized from agrowaste sugarcane bagasse. Further, hierarchical nano Fe(0) – FeS was anchored on cellulose nanofibers to obtain CNF-Fe(0)@FeS and it was characterized by various spectral techniques. Formation of FeS 2 was confirmed by high resolution TEM and XPS techniques. Anchoring on cellulose nano fibers prevented agglomeration of nanocomposite and furthermore, coating of FeS 2 helped in the preservation of Fe(0). Thus the prepared nano composite was very effective in the removal of cationic Methylene blue (MB) dye and anionic Congo red (CR) dye with a maximum adsorption capacity of 200.0 and 111.1 mg/g respectively. Both MB and CR dye followed Pseudo second kinetic with regression coefficients >0.98. Especially for MB dye, it was observed that kinetics of adsorption/degradation was very fast and within 3 min, peak at 370 nm disappeared and 70% reduction in intensity was observed at 660 nm. Further FTIR and XPS revealed evidence for the degradation of adsorbed dye molecules. Considering its high adsorption capacity, degradation potential and ease of preparation using agrowaste makes CNF-Fe(0)@FeS a promising sorbent for the treatment industrial dye effluents. [ABSTRACT FROM AUTHOR]

The adsorption of Acid Red 10B from aqueous solution has been studied in a fixed bed adsorber using raw and activated petroleum coke as an adsorbent. The activation of the petroleum coke was done with different impregnation ratios of petroleum coke with KOH, activation time and activation temperature to find the best activation condition. The activated petroleum coke is used for the fixed bed adsorption and various experimental parameters have been studied on dye removal. It is observed from the present experiment that petroleum coke is an effective adsorbent for adsorption of dye using a fixed bed adsorber. [ABSTRACT FROM AUTHOR]

In the present investigation, date seed-derived biochar was applied as economic and effective sorbent for remediation of reactive dye from contaminated solutions. Biochar produced at 350°C through pyrolysis process exhibited reactive black 5 (REB5) sorption capacity 2.7 times higher than virgin date seeds. The surface of biochar was analyzed through Fourier transform infrared and scanning electron microscope data. The maximum REB5 uptake determined through the Langmuir model was found to be 113.4 mg/g. The REB5 sorption kinetics were accurately described by the pseudo-first-order model than pseudo-second-order model. Thermodynamic parameters indicated that REB5 sorption was spontaneous, feasible, and endothermic process. [ABSTRACT FROM AUTHOR]

Textile industries releasing large amount of effluent which contains textile dyes and toxic chemicals and it is one of the major source of pollution also contaminating water bodies. To remove that, bacteria have been of great attention because of their ability to treat effluent. The present study was undertaken to exploit the ability of Pseudomonassp and Bacillus sp from dye contaminated soil samples for bioremediation for dye effluent. Among the bacterial strains used in the study. Pseudomonas sp emerged out to be most potent decolorizer in comparison to Bacillus sp with the degree of decolorization of 90.0 %. Thus, it was concluded that the Pseudomonas sp had highest color removing capacity from contaminated effluent soil samples. [ABSTRACT FROM AUTHOR]

Integrated water resources management practice is gaining popularity as an alternative water source due to the limited supply of freshwater. The present study was carried out on the photocatalytic degradation of Direct red 28 (DR-28) dye using magnetic nanoparticles (MNPs; Fe3O4) as a photocatalyst. The study was conducted on the photocatalytic degradation of DR-28 dye in synthetic dye effluent water, to understand the effects of different photoreaction parameters on the degradation kinetics. The influence of different parameters such as time, amount of photocatalyst, concentration of H2O2 and pH was investigated. At the optimum dosage of MNPs (0.6 g/L) with 4 mmol/L of H2O2, significant photocatalytic degradation of DR-28 dye (93.2%) was observed. The kinetic study revealed that the photocatalytic degradation followed pseudo-first-order kinetics. The degradation performance of Fe3O4 nanoparticles as a photocatalyst for DR-28 dye was compared with titanium dioxide (TiO2) and it was found that the performance of Fe3O4 as a photocatalyst is superior to TiO2 photocatalyst. The real dye effluent was also degraded at optimum conditions and promising results were achieved. [ABSTRACT FROM AUTHOR]

Biochar dye adsorbents are touted as "green" and low-cost compared to metals/oxides and polymers. However, the most active of them require some form of multi-step chemical activation with toxic chemicals which tarnish their credentials. Going forward, there is a need to develop low-toxic chemical activators or discover new biomass sources that can generate high-value biochar adsorbents via physical activation. Herein, we demonstrate that unlike other biomass waste almond skin (WA-s) contains a unique network of lignocellulosic capillary-like structures (CN) buried inside a dense lignocellulosic shell. Via one-step carbonization at 900 °C under N 2 , the shell is removed exposing CN which transforms into defect-rich carbon macrostructures (AS-C-T). Data from spectroscopy analysis indicate that AS-C-T has the special ability to undergo carbonylation, at high temperatures, creating moderate acidic carbonyl (C O) interfaces that form selective hydrogen bonds with the acidic hydrogen of zwitterion methyl blue (MB), at pH 6.2 to 7.2. Such interactions induce high MB adsorption capacity (>3000 mgg−1) and selectivity comparable to the state-of-the-art. The hydrogen bonding is strong and irreversible; however, it creates secondary interfaces which ensure high recyclability. The adsorption reaction is endothermic and modeled by the pseudo-second-order kinetic, Langmuir, and Intra-particle diffusion. Practically, AS-C-T can be retrofitted to commercial filters to produce pathogen- and dye-free water. These properties make AS-C-T a potential "green" and low-cost adsorbent for dye effluents. Our results hint at the fact that biomass sources with intricate capillary structures might have unique interfacial properties which are useful for preparing high-value biochar adsorbents without chemical activation. [Display omitted] [ABSTRACT FROM AUTHOR]

Dye effluents pose severe environmental hazards. Devising cost-effective and eco-friendly techniques for treating wastewater containing dye effluent is the need of the day. The intention of the present study is to expose a technique for decolorizing the dye effluents, for degrading the contaminants present in the effluent and for minimizing the COD below standard limits. The dye effluent samples collected for the present study characterize a high COD of 972 mg/L, pH 8.6 and highly objectionable color (990 Hazen Units). The predominant indigenous organisms present in the samples were isolated and identified as Aspergillus niger and Aspergillus flavus. Potential exogenous organisms Trichoderma viride and Aspergillus fumigatus were obtained, and these organisms were used to conduct treatability studies. An up-flow immobilized column reactor (UFICR) was designed and used to treat the textile effluent. The shaker flask trials give maximum decolorization efficiency of 91% and COD reduction of 84%. The reactor studies showed elevated efficiencies of 92.7% and 93% efficiency in decolorization and COD reduction, respectively. The present study is developed as an efficient strategy to replace the less eco-friendly physicochemical approaches and also to provide a better insight into the field of bioremediation and its role in the treatment of dye effluent. [ABSTRACT FROM AUTHOR]

This study evaluated impact of untreated dye effluent on heavy metal uptake by Amaranthus cruentus L. under field condition. Amaranths grown for two consecutive dry seasons were irrigated with dye effluent concentrations of 0 (control) 10, 20, 30 and 40%. Effluent concentrations were analyzed for physico-chemical and heavy metal properties. The result showed that heavy metals taken up and accumulated in amaranths tissues increased significantly ( p ≤ 0.05) with dye effluent concentration. Heavy metals accumulated more in edible shoots than roots except chromium. Bioaccumulations of heavy metals in 2012 were in several folds higher than in 2011 dry season. In the second season, regardless of effluent sources, dye concentration of 20% gave the highest accumulations of Manganese (Mn), Iron (Fe) and Zinc (Zn) in the edible shoots. The highest accumulations of heavy metals were higher than 0.3 mg kg −1 allowable limits in vegetables by Food and Agricultural Organization/World Health Organization/Federal Environmental Protection Agency. Irrigation of vegetable with untreated dye effluent should be discouraged due to potential health risks on human and general contamination of the environment. [ABSTRACT FROM AUTHOR]

Efficiency of white-rot fungi- Stereum ostrea ( S. ostrea) as a test culture and Phanerochaete chrysosporium ( P. chrysosporium) as a reference culture in colour removal from a textile dye, Remazol brilliant blue-19 (RBB-19) in medium was compared in this study. S. ostrea was more efficient than P. chrysosporium in decoloration process. Different parameters pH, temperature, sources of carbon and nitrogen, stationary and shaking conditions were optimized for bleaching of dye by the fungal cultures. Optimal growth conditions for decoloration of dye by both cultures were pH 5.0, temperature 35 °C, glucose and fructose as best carbon source at 1 % level, peptone and urea as best nitrogen source and shaking conditions (150 rpm). Culture broth free of colour (99 % of decoloration) was achieved with S. ostrea as against 70 % decoloration by P. chrysosporium on 6th day of incubation. Adsorption of dye to fungal biomass as reflected by colour coating on biomass and participation of lignolytic enzymes in colour removal appeared to be mechanisms involved in decoloration process. The ability of both fungal cultures in removal of colour in effluents with dyes collected from silk saree-weaving cottage unit was tested. S. ostrea was also found to be more effective in colour removal from effluent. S. ostrea appears to be a promising culture for application of bioremediation in decoloration of dyes. [ABSTRACT FROM AUTHOR]

Effluent collected from a dye industry in Tirupur, Tamilnadu, India, was screened for potential indigenous micro-organisms to treat remazol dyes and dye effluents. Out of sixty strains isolated, four strains were found to be potential in degrading the dye effluent and various remazol reactive dyes. The physicochemical characterisation of the dye effluent showed quite high values. Decolourisation studies were performed for two different effluents (I & II) and observed maximum decolourisation of 76.4% at 120 h (Effluent I) and 79.9% at 96 h (Effluent II) by the organism EI25. The synthetic dyes Remazol Red RGB (RR-RGB), Remazol Red RR (RR-RR), Remazol Yellow RGB (RY-RGB) and Remazol Yellow RR (RY-RR) showed complete decolourisation (100%) after 24–72 h by two potential strains (EI05 and EI25). EI25 have shown the maximum efficiency of 87.2, 95.1, 89.4 and 84.4% decolourisation for RR-RGB, RR-RR, RY-RGB and RY-RR, respectively, within a 24 h time period. Morphological characteristics and biochemical screening tests identified the organisms to beClostridium butyricumandClostridium acetobutylicum.C. acetobutylicum(EI25) was found to be the most potential strain isolated. Biodegradation of remazol dyes was characterised by spectral analysis using UV–Visible spectroscopy and FTIR spectroscopy. The peak disappearance in UV spectrum is at theλmax519 nm for RR-RGB and RR-RR; whereas, 410 nm for RY-RGB and 419 nm for RY-RR stands as the proof of decolourisation. In the FTIR spectrum, the shift of several important peaks responsible for the functional groups N=N, S=O and phenolic O–H corresponding to the structure of remazol group of dyes and appearance of new peaks indicating the degradation metabolites observed in the decolourised samples ensures biodegradation. Further, EI25 have also shown marked reduction in the basic wastewater characteristics like COD, BOD, TDS, EC and pH. Thus it is concluded that theClostridiumspecies on further studies can be well developed into a biological method of textile effluent treatment process. [ABSTRACT FROM PUBLISHER]

Polyelectrolyte complexes (PECs) have received considerable attention in resource recovery from wastewater and enhanced separation technologies because they are multicomponent polymeric materials with unique wettability properties. From this perspective, we focused on new opportunities to develop photothermally effective PECs to separate oil/water emulsion and purify dye-contaminated wastewater. The PEC was also utilized for solar steam generation. Chondroitin sulfate (CS), a weak anionic polyelectrolyte material, was treated with a cationic copolymer of poly (acrylamide-co-diallyldimethylammonium chloride) (PAAm-DADMAc). This material is used as a membrane by modifying cellulose acetate filter paper. The formation of PECs was confirmed using various analytical techniques, and a cauliflower-like assembled microparticle morphology was achieved. The surfaces of the fabricated PEC self-assembled microparticles exhibited good emulsion separation efficiency (99.4%) and emulsion permeation flux of 2316 L m−2 h−1 bar−1 after eight filtration cycles. The versatile functional groups were recognized for their superhydrophilicity and underwater superoleophobic nature (approximately 150° of contact angle) for low-and high-viscosity oils. The abundance of functional groups in the PECs treated anionic Congo red dye, cationic methylene blue dye, and textile dyeing industrial effluent with 99% separation efficiency. In addition, PEC-modified membrane materials were successfully utilized as an effective solar steam generation to purify 3.5% NaCl contaminated water under 1 kW m−2. The evaporation rate was retained with 2.31 kg m−2 h−1 for five cycles. Overall, the proposed CS/PAAm-DADMAc/GO-modified membranes can offer a new route to treat oil-in-water emulsions and remove dye from wastewater at an industrial level along with solar desalination. Thus, the proposed materials will provide essential insights into scientific and practical accessibility for developing multifunctional membrane materials for wastewater treatment. • Polyelectrolyte materials derived from Chondroitin sulfate and PAAm-DADMAc. • Polyelectrolytes with GO exhibited 99.4% separation efficiency with emulsion. • Efficient membrane separation for oil-in-water and dye mixed emulsions. • Bio-inspired membrane is utilized for industrial effluent removal. • Modified membrane material is exploited as effective solar steam generator. [ABSTRACT FROM AUTHOR]

Graphene oxide can be used to store energy, as electrodes and purify industrial and domestic wastewater as photocatalysts and adsorbents because of its remarkable thermal, electrical, and chemical capabilities. Toward understanding graphene oxide (GO) based nanomaterials considering the background factors, the present review study investigated their characteristics, preparation methods, and characterization processes. The removal of contaminants from wastewater has recently been a focus of attention for materials based on GO. Progress in GO synthesis and surface modification has shown that they can be used to immobilize enzymes. It is possible to immobilize enzymes with varying characteristics on graphene-oxide-based substrates without sacrificing their functioning, thus developing a new environmental remediation platform utilizing nano biocatalysts. GO doping and co-doping with a variety of heterogeneous semiconductor-based metal oxides were included in a brief strategy for boosting GO efficiency. A high band-gap material was also explored as a possibility for immobilization, which shifts the absorption threshold to the visible range and increases photoactivity. For water treatment applications, graphene-based nanomaterials were used in Fenton reactions, photocatalysis, ozonation, photo electrocatalysis, photo-Fenton, and a combination of photon-Fenton and photocatalysis. Nanoparticles made from GO improved the efficiency of composite materials when used for their intended applications. As a result of the analysis, prospects and improvements are clear, especially when it comes to scaling up GO-based wastewater treatment technologies. [Display omitted] • Nano-based graphene oxide (GO) is useful in effective wastewater treatment. • To develop GO to treat wastewater, bottom-up and top-down approaches can be used. • Electro-chemical, mechanical, and surface properties of GO are pollutant traps. • GO plays an important role in adsorption-based water treatment systems. [ABSTRACT FROM AUTHOR]

Highlights: [•] The COD met the discharge standards after the Fenton-coagulation treatment. [•] The acute toxicity of dye effluent was removed after Fenton-coagulation process. [•] The dye effluent exhibited no significant genotoxicity after treatment. [ABSTRACT FROM AUTHOR]

Electrochemical treatment of small-scale dyeing unit effluent containing Reactive Yellow 86, Indanthrene Blue RS, Basic GR 4 and Reactive Yellow 145 dyes was carried out with aluminium electrodes in batch mode of operation. The effluent was characterized for various parameters. The experiments were performed for 120 min, keeping the inter-electrode distance at 3 cm with a current density of 0.0625 A/cm2; the colour removal efficiency was determined for each of the four dyes. A colour removal efficiency of >97% was obtained for each of the dyes for an electrolysis time of 120 min. Further experiments were performed using aluminium sulphate as chemical coagulant to compare the colour removal efficiencies obtained by electrocoagulation and chemical coagulation. [ABSTRACT FROM PUBLISHER]

Box-Behnken design was employed for the decolourization of synthetic dye bath effluent using solar induced photo catalytic degradation with mixed semi conductor catalysts. Four independent variables namely concentration of dye effluent, catalyst loading, pH and irradiation time was chosen as process variables. The optimum concentrations of dye effluent, catalyst dosage, pH, and irradiation time were found to be 60 mg L, 200 mg L, 7 and 100 min, respectively, for maximum decolourization of dye effluent (91.24%). Predicted values were found to be in good agreement with experimental values and as a result reflected the precision and the applicability of Response Surface Methodology (RSM) (R=0.9785 and Adj R= 0.9569). [ABSTRACT FROM AUTHOR]

Abstract: Degradation of Procion Scarlet a reactive dye in dye effluent is investigated by electrochemical and biological oxidation in individual, combined and integrated methods. The main objective of the present work is to reduce the COD and colour of the dye effluent containing Procion Scarlet dye. The influence of various experimental parameters such as COD, colour, power consumption and mass flux were calculated and presented. Microbiological experiments were performed by bacteria which is isolated from textile outlet site soil. From the results, individual electro oxidation process maximum COD removal of about 80% and colour removal of 97.9% was achieved at an optimum current density of about 10.25A/dm2 whereas bio-oxidation process reduced COD and colour removal of about 50% and 42.4% respectively. Integrated process reduced the COD and colour removal of 80% and 96.4% respectively at an optimum current density range of 6.84A/dm2, whereas combined processes showed the COD and colour removal of 90% and 98.5% respectively at an optimized current density of 7.6 and 10.2A/dm2. After post treatment the treated effluent can be reused. [Copyright &y& Elsevier]

Abstract: Potatoes are desirable source for polyphenol oxidase (PPO, EC 1.14.18.1) purification because this enzyme can be purified from the food industry waste such are potato peels from potato chips industry. This paper presents data concerning decolorization of 7 different, so far untested textile dyes and 3 real samples (industry effluents) by a partially purified PPO. Under optimized conditions 93–99.9% removal of dyes was achieved after 1 h using 424–1700 U ml−1 of PPO, depending on dye. Optimum pH for decolorization process of all dyes was found to be 3.0. Potato PPO was capable of removing reactive dyes and textile dye effluents without requiring any mediator. Decolorization was accomplished via insoluble polymers formations that were separated by filtration. [Copyright &y& Elsevier]

Abstract: A complex Remazol dye effluent, comprised of Remazol Brilliant Blue R, Remazol Black, Remazol Violet, Remazol Orange, sodium chloride, sodium carbonate, sodium hydroxide, and acetic acid, was decolorized using polyaniline/extracellular polymeric substance (Pn/EPS) composite. Scanning electron micrograph showed that the surface of the composite was rough with granular appearance, providing a good possibility for dyes adsorption. X-ray diffractogram (XRD) of the composite showed the main reflections of both Pn and EPSs (2θ =6.0, 20.1 and 26.2, 30.4, and 40.8). Experiments were carried out as a function of contact time, pH, and adsorbent dose. Under optimized conditions, the maximum percentage removal was found to be 99.8% for the complex Remazol effluent. The Freundlich isotherm model and pseudo first-order rate expression showed satisfactory fit to the equilibrium biosorption data of Pn/EPS composite. Fourier transform infrared spectroscopy, XRD, and desorption studies confirmed the involvement of aromatic, amino, hydroxyl, and carboxylic groups in dye adsorption. The results indicate that composite is suitable as an adsorbent material for the enhanced removal of dyes from complex Remazol effluent. [Copyright &y& Elsevier]

A simple process, vacuum distillation, was utilized for purification of methyl orange (MO) as dye effluent. The dye effluent characteristic of high chemical oxygen demand (COD) value and high chromaticity is difficult to treat for the industrial wastewater treatment. In our work, the effect of some factors on the distillation efficiency (DE), including pressure, concentration and the surfactant based on the optimal conditions was evaluated. The results showed that the COD removal for 99.57% was obtained when the concentration of MO is 2000 mg l-1 at the pressure of 0.070 MPa. Moreover, the polyacrylamide (cationic) used in initial concentration of 500 mg l-1 show satisfactory removal efficiency in the further test. [ABSTRACT FROM AUTHOR]

A non-ligninolytic fungus Myrothecium sp. IMER1 and its bilirubin oxidase (BOX) were evaluated for their ability to decolorize an alkaline dye effluent. The strain was capable of decolorizing dye effluent at various concentrations of 20, 33.3, 50 and 66.7% (v/v) in the pH basic range of 9.5-10.0, but high dye effluent concentration in the medium resulted in low colour removal rate. The biomass production and BOX activity of Myrothecium sp. IMER1 were inhibited during decolorization. Spectra analyses of culture supernatants and colour changes in fungal cells suggested that dyes in the effluent were removed by Myrothecium sp. IMER1 mainly due to enzymatic reaction. Thus, biodegradation was the major dye decolorization mechanism, rather than inactive surface adsorption. BOX was able to decolorize dye effluent effectively over a pH range of 4-10, and maximum decolorization of dye effluent was observed at pH 7.0. In addition, colour removal efficiency was higher at neutral and alkaline pH than at acid pH. In the presence of 2,2-Azinobis (3-ethylbenzothiazolin-6-sulfonic acid) (ABTS) as a redox mediator, a marked increase was obtained in decolorization at the various pH values tested. The germination of Phaseolus mungo seeds was inhibited with dye effluent but not with the dye effluent treated by Myrothecium sp. IMER1 or BOX, indicating the less toxic nature of the treated dye effluent to the plants. Therefore, both this non-ligninolytic strain and its extracellular BOX will be potential candidates for wastewater treatment of dye effluents, especially alkaline dye effluents. [ABSTRACT FROM AUTHOR]

Abstract: Dyeings on cotton obtained using three commercial bifunctional reactive dyes were subjected to a standard, five-stage method which employed a proprietary wash-off agent as well as a three stage, chemical-free wash-off process. Dyeings obtained using both wash-off methods were of the same colour and displayed similar levels of fastness to repeated washing at 60 °C. Lowering the number of wash-off stages from five to three and replacing the wash-off agent with 98 °C water rinses reduced considerably, both the COD and, especially, BOD5 compared with the standard wash-off method, with no increase in COD/BOD5 ratio. The three-bath wash-off method therefore offers potential savings in water usage, compared to the standard method and also eliminates the need for chemicals to be employed in wash-off. [Copyright &y& Elsevier]

Abstract: Dyeings on cotton obtained using three commercial reactive dyes were subjected to three wash-off processes namely, a standard, five-stage method which used a proprietary wash-off agent, a five-stage process in which Na2CO3 was used in place of the commercial wash-off agent and a three-stage, chemical-free method. Dyeings that were generally of the same hue and colour strength and which also displayed similar levels of fastness to repeated washing, were obtained using each of the three wash-off processes. The replacement of the commercial wash-off agent in the five-stage, standard wash-off process with Na2CO3 reduced, considerably, both the COD and BOD5 loads of the residual wastewater; the corresponding COD/BOD5 ratios showed an improvement in the biodegradability of the residual wastewater. Although reducing the number of wash-off stages from five to three and replacing Na2CO3 with 98 °C water rinses increased both COD and BOD5 loads, the ensuing biodegradability of the residual wastewater was improved. Thus, by using a three-bath, water-only wash-off process, not only was the amount of water used for reactive dye wash-off reduced but also the wastewater generated was of higher biodegradability. [Copyright &y& Elsevier]

Abstract: The high energy cost of an electrochemical method is the fatal drawback that hinders its large scale application in wastewater treatment. The traditional single-chamber electrochemical method used in the waste water treatment mainly focused on anodic oxidation, but hydrogen produced on the cathode and indirect electrochemical treatment involves application of an electrical current to the wastewater containing chloride to convert into chlorine/hypochlorite. The two-compartment electrolytic cell, separated by an anion exchange membrane, has been developed in this work. In the new reactor, indirect oxidation at anode, indirect oxidation by hydrogen peroxide and ultraviolet/hydrogen peroxide (UV/H2O2) at cathode can occur simultaneously. The electrochemically produced hydrogen peroxide at the cathode by reduction of oxygen is affected by passing atmospheric air. Therefore “dual electrochemical oxidation” in one electrochemical reactor was achieved successfully. Compared to a traditional one-cell reactor, this reactor reduces the energy cost approximately by 25–40%, and thus the present work becomes significant in wastewater treatment. Experiments were carried out at different current densities using Ti/RuO2/IrO2 as anode and carbon felt gas diffusion electrode used as a cathode fed with oxygen containing gases to produce hydrogen peroxide. During the various stages of electrolysis, the parameters such as, effect of pH, chemical oxygen demand (COD), colour, energy consumption were monitored. UV–vis spectrometry, Fourier transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC) studies were carried out to assess efficiencies of dye degradation. [Copyright &y& Elsevier]

Phytoremediation is a promising green technology for the remediation of various industrial effluents. Notably, aquatic plants are widely applied to remove dyes and toxic metals from polluted environments. In the present study, the phytoremediation potency of aquatic macrophytes such as Pistia stratiotes L, Salvinia adnata Desv, and Hydrilla verticillata (L.f) Royle were assessed based on the removal capability of pollutants from dyeing effluent. Physicochemical characterizations were carried out for industrial wastewater collected from a cotton material dyeing unit located in the Karur District of Tamilnadu, India. The physicochemical characteristics of the dyeing effluent, such as color, odor, pH, total dissolved solids (TDS), alkalinity, acidity, chloride, sulfate, phosphate, nitrate, chemical oxygen demand (COD), fluoride, and toxic metal levels were determined. The core parameters such as total dissolved solid (TDS), chemical oxygen demand (COD), and chloride level were determined and found to be 6500 mg/L, 2400 mg/L, and 2050 mg/L, respectively, which exceeded the regulatory limit prescribed by the Central Pollution Control Board of India. The levels of toxic metals such as Hg, Ni, and Zn were under the acceptable concentration but Cr and Pb levels in the dyeing effluent were a little bit higher. The effluent was subjected to treatment with Pistia stratiotes L, Salvinia adnata Desv and Hydrilla verticillata (L.f) Royle separately. After the treatment, the toxic metal results were recorded as below detectable levels and the same results were obtained for all three aquatic plants samples used for treatment. Among the three plants, P. stratiotes L efficiently removed 86% of color, 66% of TDS, 77% of COD, and 61.33% of chloride. The variation in phytochemicals of the macrophytes was studied before and after treatment using GC–MS which revealed the reduction of ascorbic acid in the plant samples. The toxic effect of treated effluent was investigated by irrigating an ornamental plant, Impatiens balsamina L. The plant biomass P. stratiotes L obtained after the treatment process was subjected to manure production and its nutrient quality was proved, which can be applied as a soil conditioner. Among the aquatic plants, the results of P. stratiotes L indicated a higher remediation potential, which can be used as an ecologically benign method for treatment of industrial effluents and water bodies contaminated with dyeing effluents. [ABSTRACT FROM AUTHOR]

Using DMAc as solvent, water as non-solvent, modified poly (vinylidene fluoride) (PVDF) ultrafiltration membranes (PSi, PA, PS) were prepared by precipitation phase inversion, blending with nano-silica (SiO2), polyvinyl alcohol (PVA), and styrene maleic anhydride. The physical-chemical properties and morphology of PVDF membranes were characterized by FT-IR, water contact angle (WCA), swelling index, scanning electron microscopy, atomic force microscopy, etc. Considering reactive black 5 and congo red as the representatives of dye effluent pollutions, the filtration behavior to dye wastewater of four different types of PVDF UF membranes was discussed. Experimental results showed that, compared with original PVDF UF membrane, for three kinds of modified membrane, the first bubble pressure and strength (S) fell off to a certain extent, and the membrane surface roughness increased. Additionally, the cross-sectional macroporous and pure water flux (J) all increased. Especially, owing to the addition of PVA and SiO2, the WCA and the adsorption amount (Q) of PA and PSi membranes were reduced extraordinarily, and flux recovery rate increased obviously. As a result, the hydrophilicity of PVDF membrane was improved significantly. Moreover, the rejection (r) to two dyes was also remained well, which showed a better anti-fouling ability. [ABSTRACT FROM AUTHOR]