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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]

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]

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]

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]

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]