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Dye removal from wastewater is of prominence due to its hostile effects on human health and the environment. The complex structure of the dye molecule is responsible for its difficulty in removal. Adsorption is found to be a promising technique to eliminate dye wastes due to its high removal capacity at low concentration. Among different adsorbents used, hydroxyapatite is a biocompatible adsorbent that is relatively efficient in both anionic and cationic dye removal. Recently, modification of hydroxyapatite by doping with other materials to increase its removal efficiency has gained much attention. This review summarizes compilation of recent literature on the removal of anionic and cationic dye by different hydroxyapatite nanocomposites, comparison of adsorption capacities of different hydroxyapatite nanocomposites, the possible adsorption mechanism of removal of dyes, the general isotherm, and kinetic and thermodynamic studies explaining the type of adsorption and the characteristics, advantages, and limitations of adsorbents.

Textile printing and dyeing wastewater is usually characterized by high pH, high turbidity, poor bio-degradability, complex composition, and high chrominance, and is discharged in large amounts. It has been regarded as one of the hardest to treat forms of industrial wastewater. Conventional physicochemical technologies can remove these contaminants from water bodies, but at the expense of high energy consumption and high cost. Alternatively, biological processes with limited energy consumption, low cost and high efficiency are considered as promising technologies. Among them, the anaerobic biological processes have been proven to be effective for the treatment of high-concentration textile printing and dyeing wastewater. In this mini-review, recent advances on high-rate anaerobic technologies for such purposes are reviewed. Current limitations of these technologies are summarized, and future research directions are indicated.Graphical abstract

Textile industry effluents and landfill leachate contain chemicals such as dyes, heavy metals and aromatic amines characterized by their mutagenicity, cytotoxicity and carcinogenicity. The aim of the present study was investigation of the ascomycete fungus N. pironii isolated from urban postindustrial textile green space for its ability to grow and retain metabolic activity in the presence of the dye industry waste. Research focused mainly on dyes, heavy metals and aromatic amines, which had been detected in landfill leachate via HPLC–MS/MS analysis. Presence of all tested compounds as well as leachate in the growth medium clearly favored the growth of fungal biomass. Only slight growth limitation was observed in the presence of 50 mg L -1 o -tolidine. The fungus eliminated o -tolidine as well as dyes at all tested concentrations. The presence of metals slightly influenced the decolorization of the azo dyes; however, it was still similar to 90%. During fungal growth, o -tolidine was hydroxylated and/or converted to toluidine and its derivatives. Laccase and cytochrome P450 involvement in this process has been revealed. The results presented in the paper provide a valuable background for the development of a fungus-based system for the elimination of toxic pollutants generated by the textile industry.

Adsorptive removal of dyes from industrial wastewater has attracted intensive interests in recent years. Hydrogels is a kind of promising adsorbent in dyes removal owing to the simple synthesis and convenient application. A biodegradable and recyclable gelatin hydrogel (GH) was synthesized by a convenient approach in this work. The as-prepared GH was used to remove dyes in aqueous solution. The results indicated that the GH had excellent adsorption capacity for various dyes and the maximum adsorption capacities of crystalline violet (CV), methyl orange (MO), acid fuchsin (AF), congo red (CR), malachite green (MG), and methylene blue (MB) were 138.89 mg/g, 72.63 mg/g, 66.29 mg/g, 64.84 mg/g, 64.64 mg/g, and 60.32 mg/g, respectively. Moreover, the dye removal efficiency was still more than 60% after five consecutive adsorption–desorption cycles and the shape of the GH kept well. Therefore, GH can be used as an environmentally friendly and effective adsorbent to remove virous dyes from printing and dyeing wastewater.

In the modern era, with the rapid growth of various industries, the issues of energy crisis and environmental pollution have garnered increasing attention. One significant source of industrial pollution is printing and dyeing wastewater. This wastewater often contains dyes that have aromatic structures and azo groups, such as Methyl orange (MO), which are both toxic and difficult to degrade. If these dyes are released into the wastewater stream without any treatment, they can have adverse effects on ecological balance and human health. Therefore, it is crucial to identify suitable treatment strategies to efficiently remove dyes from wastewater systems before discharge. In this study, the Methyl orange (MO) azo dye has been removed from dyes-contaminated wastewater, for the first time, using a novel amino-ethyl carboxymethyl cellulose crosslinked ampholyte hydrogel (AECMC). Different characterization methods, including FTIR, TGA, and DSC were used to characterize the generated AECMC compounds. The water absorption and cationic exchange capacities were assessed. Factors affecting the MO anions adsorption including MO concentration, adsorption pH, temperature, time, adsorbent dose, and agitation speed have been investigated. Moreover, the kinetics of the adsorption process was assessed by the use of three models: pseudo-first-order, Pseudo-second-order, and Elovich. Moreover, the mechanism of the adsorption process was monitored using the Intraparticle diffusion and Boyd models. Additionally, the adsorption isotherm was examined using established models such as Langmuir, Freundlich, and Temkin isotherms. The thermodynamic characteristics of the MO adsorption process have been investigated at various adsorption temperatures using the Van't Hoff model. The results obtained from the study indicate that the process of MO adsorption adhered to the Pseudo-second-order kinetic model, the Langmuir isotherm model was found to be applicable, and spontaneous and exhibited an endothermic character. In conclusion, the developed novel amino-ethyl carboxymethyl cellulose crosslinked ampholyte hydrogels (AECMC) have successive in the removal of the MO anionic dye from contaminated wastewater.

Gajah Mungkur Gresik Printed Batik Business is a printed batik industry with the main motif being the Gajah Mungkur. So far, the production process of printed batik, especially in the printing section, has been considered not to be good because the liquid waste in the form of dyes produced is huge, and waste management has not been carried out properly. This study aims to determine the percentage of clean production implementation and the weight of alternative solutions in the Gajah Mungkur Gresik Printed Batik Business. The research method used is the Analytical Hierarchy Process (AHP) analysis. The results of the study showed that the alternative solutions chosen in the implementation of clean production in Gajah Mungkur Printed Batik Business were to create standards for measuring and mixing dyes, provide training and workshops on dye waste management, create new SOPs for routine machine checks and maintenance, tighten quality control of dye supplies, and collaborate with other business units that can process liquid dye waste.

Anthraquinone dyes, which include an anthraquinone chromophore group, are the second-largest among dye classes, which is often employed in textile manufacturing. A significant number of anthraquinone dyes get into the environment, creating severe pollution since many of these dyes have intricate and stable structures. Currently, microbiological treatment of wastewater is an economically and feasibly viable solution for treating printing and dyeing wastewater, and there are growing reports of biodegradation of anthraquinone dyes. In this review, we outline the current advances in the biodegradation of anthraquinone dyes, summarizes dyes biodegradation by bacterial, fungal, and algae strains, factors influencing dyes biodegradation, current methods in enhancing dyes biodegradation, resuscitation of viable but non-culturable (VBNC) bacteria for better microbial performance, and potentials of VBNC bacteria in degrading dyes. Finally, future directions and important areas for study are given, and such efforts are anticipated to improve the anaerobic degradation process.

The textile industry is expanding globally and is considered the backbone of the world’s largest source of foreign exchange. The development of the textile industry has caused environmental contamination due to its dye waste, which is complex and very difficult to resolve with chemical and physical treatments. Azo dye is one of the most widely used dyes in textile and other industries. It is one of the significantly toxic dyes, and when released in water bodies, it causes a serious threat to the environment. A bacterial strain having the potential to degrade a variety of azo dyes such as Congo red (CR), methylene blue (MB), Alizarin Red S (AR), and Remazol Brilliant Blue R (RBBR) was isolated from soil samples in the wood weathering area and further identified and characterized. Ligninolytic microorganisms produce laccase enzymes, lignin peroxidase, manganese peroxidase, and other enzymes that can decolorize dye waste from the textile industry. The research phase was qualitative and quantitative tests of ligninolytic bacteria in the decolorization process using several selected synthetic dyes, antagonism tests, and identification of potential bacteria based on 16S rDNA gene sequences. The L11 isolate showed high performance on CR dye of 82.79%, L1 isolate on dye AR of 40.51%, L7 isolate on dye MB of 38.69%, and L8 isolate on RBBR dye of 30.34%. The L11 isolate with the highest potency was identified as Bacillus paramycoides K7.2 with a similarity of 99.71%. After 7 days of incubation, the quantitative test findings are the same as the qualitative test results, with isolate L11 having the largest clear zone on CR, AR, and RBBR dyes.

Heterogeneous photocatalysis using nanocomposites is of great research interest in the treatment of industrial wastewater. The impregnated photocatalyst was produced by liquid state reaction of ZnO/CuO nanocomposite with extracted eggshells. The structure, functional group, metal composition, bandgap, and photocatalytic activity of the nanocomposites were characterized by using X-ray diffraction, Fourier-transform infrared spectroscopy, atomic absorption spectrometry, and UV–Vis spectroscopy, respectively, in the absence and presence of eggshells. Photocatalytic degradation activities of the nanocomposites under UV light irradiation have been tested for a real sewage sample taken from Debre Berhan Textile Industry. From the results, the optimized degradation efficiency of the dye was 97.95% with 0.4 g dose of the photocatalyst, 120 min irradiation time, 120 °C temperature, and pH of 6.7. The results revealed that eggshell impregnated nanocomposite had better catalytic activity than the naked nanocomposite. This is due to the highly porous structure of eggshell biomasses and their sorption characteristics. In conclusion, when nanocomposites are supported by eggshell biomasses, they are excellent photocatalysts and can minimize the contamination of organic dyes from textile effluents.

Azolla filiculoides (AF) biomass has been tested for its performance as a biosorbent agent toward removing reactive black 5 (RB5) dyes from polluted water. The morphology and structure of the AF was characterized using several advanced techniques. To understand the mechanism of the RB5 biosorption by AF, isotherm, kinetic, and thermodynamic analyses were performed. In addition, the biosorption capacity of AF was tested under various environmental conditions such as solution pH (3–11), biosorbent dosage (0.5–8.0 g/L), contact time (up to 150 min), initial pollutant concentration (25–200 mg/L), and solution temperature (273–333 K). The results demonstrated that the biosorption process of RB5 dye onto AF was quite rapid as the biosorption equilibrium status was attained within 60 min of reaction initiation. A negative effect on the removal efficiencies was noted with increase in the pH values from 3 to 11, while the removal efficiency increase by double with the AF dose increase from 0.5 to 2.0 g/L. The kinetic study revealed that the biosorption trend conformed to the kinetic reaction of the pseudo-second-order. The determined parameters of the thermodynamic studies demonstrated the endothermic and spontaneous of the biosorption nature. Complete compatibility of the biosorption isotherm process with the Langmuir model, with regards to this model the maximum biosorption capacity reached to 41.73 mg/g under the optimized conditions (pH = 3, biosorbent dose = 4 g/L, initial concentration = 25 mg/L, and room temperature). The biosorption process occurred through both physical interactions and chemical reactions between the pollutant molecules and the biosorbent reaction sites. Our study thus revealed that AF biomass is a cheap and excellent agent with potential for application in the abatement of RB5 dye concentration in wastewater with acidic pH.