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Constructing high efficient nanostructured photocatalysts is meaningful for dyeing wastewater treatment. Herein, a new p-n heterostructured photocatalyst of NiS/BiVO 4 (NiS/BVO) was well designed, synthesized and applied to photodegrade anion organic dye. Coupling p-type NiS nanoparticles on n-type decahedral nanostructured BVO cannot obviously increase the specific surface area, but can effectively increase the light harvesting, enhance the photocurrent response, and promote the separation and transfer of the photo-generated electron-holes. As a result, 0.7 molar ratio of NiS/BVO exhibited the best photocatalytic capability of 95.6 % within 90 min irradiation, possessing the highest degradation rate of 1.7970 h−1, which is almost 16 and 33 times higher than pure BVO (15.8 %, 0.1134 h−1) and NiS (7.9 %, 0.0543 h−1). Meanwhile, NiS/BVO has well photocatalytic stability in at least five cycling tests. [ABSTRACT FROM AUTHOR]

Dyeing wastewater from textile industries is often contaminated with chemical pollutants, which causes severe water pollution problems that are challenging to treat. Recently, Zeolitic imidazolate frameworks (ZIFs) have attracted extensive research interest due to their potential applications in the removal of pollutants from wastewater. Herein, a Cd- zeolitic-imidazolate framework (Cd-ZIF-8) was synthesized and used as an adsorbent for the removal of methyl orange (MO) at different operating conditions. The prepared adsorbent was characterized using a variety of techniques, including X-ray diffraction (XRD), the Brunauer Emmett Teller (BET) method, FT-IR and scanning electron microscope (SEM). Its stability after adsorption was confirmed by XRD and pH tests. The effects of different variables, such as adsorbent dose, initial concentration, pH and temperature, were investigated to optimize the adsorption process. Adsorption parameters were determined by applying Langmuir and Freundlich models, and good fitting was observed for the Langmuir isotherm. Maximum MO adsorption capacities on Cd-ZIF-8 were 93.24 and 145.41 mg g−1 at 30° and 50°, respectively. Possible controlling mechanism and the potential rate-limiting steps were analyzed using Lagergren's pseudo-first-order and pseudo-second-order models, and the data were found to follow the pseudo-second-order equation. The prepared material was found to have good stability after the adsorption with no release of Cd ions over a wide range of pH. For a further explanation of the adsorption mechanism, interactions of MO molecules with the Cd and organic linkers of ZIF-8 were investigated using Density Functional Theory (DFT) cluster calculations. [ABSTRACT FROM AUTHOR]

In order to avoid the intensive burden of sewage treatment in the traditional dyeing process of indigo caused by the heavy usage of sodium dithionite (Na 2 S 2 O 4), an indirect electrochemical reduction dyeing method for denim fabrics was carried out. The indirect electrochemical reduction dyeing with different iron-based complexes was explored by cyclic voltammetry. In addition, the stability of the complex solution, the reduction potential of the dye solution, the rate of dye reduction (Re) and ferrous ion conversion (Xe) in the electrochemical process were investigated, which showed that the Fe(Ⅱ)-DGS-Abal B complex containing ferrous sulfate, sodium gluconate and Abal B (a complexing agent with high alkali resistance and electrical conductivity based on triethanolamine) had stronger reducing capacity. Furthermore, orthogonal experiments and gray clustering analysis were utilized to optimize the indirect electrochemical dyeing process for denim fabric. Under the optimized electrochemical reduction dyeing process, the rate of dye reduction could be up to 91.23% and the K/S value of dyed denim fabric could reach 14.75, which is 6.58% higher than that of the traditional dyeing process. Besides, the dyeing depth is nearly invariable within 7 times of cyclic dyeing and the dyeing liquid is more susceptible to biological and chemical degradation. Compared with the traditional reduction dyeing with Na 2 S 2 O 4 at higher temperature, the electrochemical reduction dyeing strategy uses electrical energy to reduce indigo at room temperature, and the reduction medium could be sustainably utilized by the circulation pump after the cyclic electrochemical reduction dyeing is completed, which not only decreases the COD value of dyeing wastewater, but also saves 63.5% of the economic cost. The eco-friendly electrochemical dyeing strategy presented here with obvious economic benefits could significantly contribute to enhance the sustainability of dyeing process for denim production. Image 1 • Electrochemical reduction mechanisms of iron-based complex systems were determined. • Gray clustering analysis was applied to optimize the dyeing process. • The rate of dye reduction could be up to 91.23%. • The dyeing liquid is more susceptible to biological and chemical degradation. • The electrochemical reduction dyeing could save about 63.5% of the economic cost. [ABSTRACT FROM AUTHOR]

The electrocatalytic activity, H 2 O 2 generation capacities and kinetics, and energy consumption of engineered carbonaceous cathodes including graphite plate, graphite felt, carbon felt, activated carbon felt and carbon fiber felt (CFF) was systematically evaluated in a double-chamber electrolysis system. The CFF cathode exhibited an excellent electrocatalytic activity in 2-electron oxygen reduction for H 2 O 2 generation in both acidic and alkaline solutions. Furthermore, Reactive Red X-3B oxidation efficacy of carbonaceous cathodes via electro-generated H 2 O 2 was compared in synthetic dyeing wastewater. The nature of carbonaceous materials dominated the degradation of Reactive Red X-3B in the cathodic chamber. Decolorization rate of more than 99% was achieved in all the cathodes tested, but there was a significant difference in the rate of mineralization. It was found that CFF was outclassed by 24.54% COD removal and high H 2 O 2 generation ability in long runs. The degradation rate constant of Reactive Red X-3B in the CFF cathode chamber was 3.3 times faster than that of the graphite felt with rate constants of 1.27 × 10−3 min−1 and 3.82 × 10−4 min-1, respectively. The desirable stability and electrocatalytic activity of CFF were attributed to the better graphitic structure, higher conductivity and electroactive surface area with N-containing functional groups. Our findings demonstrate the potential of CFF to be used as a high-efficiency cathode in the electrochemical treatment of recalcitrant pollutants in practical applications. Unlabelled Image • Electrocatalytic activity of carbonic cathodes in electrolysis systems was compared. • N-bearing CFF exhibited remarkable H 2 O 2 yield capacity in acidic and alkaline pHs. • CFF showed excellent long-term performance for electro-degradation of reactive dye. • Desirable electro-performance of CFF was mainly due to high electroactive surface. [ABSTRACT FROM AUTHOR]

Microfibers (MFs) are fibrous micro particles of longitude <5 mm, including natural fibers and fibrous microplastics. Microplastic pollution has become a world issue. As the major section of fiber production and processing, textile industry is an important potential source of microfibers, while receiving limited attention. To better understand the source and fate of textile microfibers, in this study, a typical textile industrial park in China is selected as the studying site. Microfibers in textile wastewater from typical textile mills and centralized wastewater treatments plants (WWTPs) of the park, and microfibers in nearby surface water were identified and characterized. The main results showed that the microfiber concentration in textile printing and dyeing wastewater could reach as high as 54,100 MFs/L. Although the removal efficiencies of microfibers by existing wastewater treatment processes can be over 85%, the average microfiber concentration in the effluents from the centralized WWTPs of the industrial park still reached 537.5 MFs/L, releasing 430 billion microfiber items per day. Microfiber release from textile wastewater is considerably higher than that from municipal sewage treatment plants, making it a significant contributor to microfibers in natural water bodies. Small-sized and colored microfibers increased in proportion in the treated effluents. Given the complex textile wastewater constituents, the potential negative environmental impacts of textile microfibers may be intensified by the enhanced adsorption and transfer of textile pollutants through these microfibers. Unlabelled Image • One of the largest textile industrial park in China is selected as studying site. • Textile mills are significant point sources of microfibers. • Centralized textile WWTPs release massive amounts of microfibers. • Textile wastewater can be a major source of textile microfibers in surface water. [ABSTRACT FROM AUTHOR]

• Cellulose aerogels modified by polypropylene glycol adipate were prepared. • The direct mixing method is adopted to make the preparation process simpler. • Aerogels have excellent adsorption capacity for Congo red. • The prepared adsorbent is eco-friendly. Cellulose-based aerogel is widely concerned as a new type of adsorption material. However, due to its low mechanical strength and small adsorption capacity in practical applications, it is necessary to enhance its mechanical strength through certain means. In this study, poly(propylene glycol adipate) (PPA)-modified cellulose aerogel materials were prepared with direct mixing method, and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results suggested that the modified cellulose aerogel (PCA) had a more stable network structure and more uniform pore size. The adsorption ability of the aerogel was measured by Congo red (CR), an azo dye, as an adsorbate. Analysis of the adsorption amounts, kinetics and thermodynamics towards Congo Red further confirmed the CR removal capacity of PCA, which can reach 120 mg g-1. According to the research results, the use of PPA as a modifier can effectively improve the mechanical strength of cellulose aerogel and has great potential in the treatment of printing and dyeing wastewater. [ABSTRACT FROM AUTHOR]

• Polyether amine was chosen to prepare NF membrane by interfacial polymerization. • Polyether amine endowed membrane with loose internal structure and hydrophilic surface. • The optimized membrane exhibited a high water flux as16.6 L m-2h−1 bar−1. • High salt/dye separation and antifouling performance were realized. It is crucial for fractionating dye/salt mixture in dyeing wastewater treatment. Herein, a polyamide nanofiltration (NF) membrane (PEA-TMC) for high efficient dye desalination was prepared through polyether amine (PEA) and trimesoyl chloride interfacial polymerization. Due to the large molecular size and hydrophilicity of PEA, the resulting NF membrane possessed a relatively loose membrane structure and good hydrophilicity, which improved membrane water flux and dye desalination performance. The influences of PEA concentration and reaction time on the NF performance were systematically investigated. Under the optimal conditions, the membrane exhibited a high water flux of 66.4 L m-2h−1 at low operating pressure (0.4 MPa), and showed a high methyl blue rejection (95.4%) and low NaCl rejection (16.4%) when nanofiltrated methyl blue/ NaCl mixture solution. Moreover, PEA-TMC membrane exhibited good stability in continuous operation and antifouling performance. These results disclosed the promising applications of PEA-TMC membrane in dye/salt separation process. [ABSTRACT FROM AUTHOR]

Colored wastewater has to be treated before its discharge, which is a great challenge for the protection of the ecological environment. A novel polymeric dye with nanoparticle morphology has been handily designed to dye polyester fabrics and can be fully recycled to avoid a large number of dyes discharge. It solves the colored wastewater pollution problem in the dyeing process from the source. The colored polyurethane nanoparticles with an average size of 500 nm are prepared via emulsion polymerization. The average content of the colorant monomer on nanoparticle is 2.77%. The colored nanoparticle demonstrates no thermal degradation at 110 °C and no damage under 20 MPa, which means good adaptability for the high-temperature dyeing process. The color depth of dyed polyester fabric can be easily adjusted by changing the concentration of colored nanoparticles in dyebath. The colored nanoparticles in the residual dyebath can be collected by extraction filtration leading to the concentration decreases from 11 mg mL−1 to 0.000025 mg mL−1 after filtered. Both the colored polyurethane nanoparticles and filtered water are fully reused for the next dyeing process to achieve the purpose of avoiding water consumption and residue dyes discharged. This work can promote the development of green and clean dyeing processes in the textile industry. Image 1 • Colored polyurethane nanoparticles (CPNPs) are synthesized by miniemulsion polymerization. • High temperature-pressure dyeing method is adopted to dye polyester fabric with CPNPs. • Nearly-zero pollutant discharge of dyeing wastewater is obtained. • CPNPs recycled dyeing method provides a way for clean development of textile coloring industry. [ABSTRACT FROM AUTHOR]

It is significant for electrocatalysis electrode materials to possess high degradative efficiency and future practical applications. Herein, the boron nitride (BN) modified Ti/PbO 2 electrode is prepared by an electro-deposition process. It is found that the introduction of BN plays a significant effect in tuning the morphology, and the surface hydrophilic and hydrophobic properties of the PbO 2 electrode, which enhances the electrochemical active areas, generating efficiency of hydroxyl radicals. Subsequently, organic dyes, reactive brilliant blue KN-R, is achievably degraded by the electrode with BN decoration. It is noteworthy that the promotion of electrosorption toward electrocatalytic decolorization of dyeing wastewater is also observed. This result demonstrates that the design of efficient PbO 2 anode for treating organic wastewater could be easily realized by introducing BN additive, and it also confirmed that the combination of tailored surface hydrophilic/hydrophobic characteristics and electro-sorption is a scientific strategy for improving electrocatalysis of semiconductor anode. • The better surface hydrophobicity of PbO 2 coatings arises from doping of BN. • The precipitation of BN on the PbO 2 surface is a significant factor to promote synergy between electrosorption and electrocatalysis. [ABSTRACT FROM AUTHOR]

• A novel biomass activated carbon fiber (MACFs) was first prepared by a facile carbonization strategy. • MACFs exhibited high specific surface area and hierarchical pore distribution. • MACFs showed robust adsorption capacity for methylene blue both in immersion oscillation and dynamic filtration adsorption. Activated carbon fiber (ACF) has broad application prospects in dyeing wastewater purification owing to its high specific surface area and hierarchical pore distribution. Natural fiber based ACFs is a group of emerging biomass adsorbent with attractive potential adsorbent properties. Herein, we develop a facile carbonization strategy to obtain a novel biomass ACF derived from the seed hair fibers of metaplexis japonica (MACFs), and the prepared MACFs possess hollow structure and the formation of graphite-like crystallites from MACFs is promoted by high temperature of carbonization. MACFs possess well-developed pore distribution, with a maximum specific surface area and total pore volume of 1882.003 m2/g and 1.613 cm3/g, respectively. MACFs exhibits the maximum adsorption capacity to be 943.372 mg/g for methylene blue (MB) fitting well with Langmuir model. Furthermore, MACFs can adsorb full solution of 90 mg/l by filtering only one time, proving its fast-adsorption performance. The high adsorption capacity and speed of MACFs are mainly attributed to three factors: high specific surface area and rich pores benefited from the full activation of hollow fibers, strong electrostatic attraction to MB provided by surface groups, and good contact with dye liquor. This work may shed light of the adsorption mechanism of biomass ACFs for the dyeing molecules and pave the way for the development of low-cost and highly efficient adsorbent. [ABSTRACT FROM AUTHOR]

Core-shell nanoparticles were prepared by coating magnetic nanoballs (Fe3O4) with highly cross-linked polymer poly(-cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) to serve as heteroatomic-rich doping electrodes (MZPS). After formation by carbonization, C-MPZS acts like a flowing electrode used for flow-capacitive deionization (FCDI), which has fast ion transfer and diffusion performances because of its rich heteroatom content and the prominent synergistic effect of N, P, S atoms. Moreover, the FCDI performance of C-MPZS is enhanced due to its increased synergistic effect from its excellent available specific surface area, unique porous characteristics with large micro-/mesopores, and favorable conductivity with high graphitization. The optimal carbonization temperature was 500 °C with an optimum specific capacitance of 211.54 F g−1, which was tested in a 1 M sodium chloride solution at a scan rate of 1 mV s−1. Then, the C-MPZS flowing electrode was found to have a high electrosorption capacity (50.07 mg g−1), removal efficiency (68.50%) and removal rate (83.07%) at an applied potential of 1.0 V in a sodium chloride solution with a conductivity of 1200 μS cm−1 at 6 rpm. An additional cyclic test demonstrated good stability performance after 10 cycles due to the magnetic nanoparticles effect. Finally, through the successful application in tail water from printing and dyeing wastewater, the results indicated that the as-prepared C-MPZS flowing electrode has promise for application in high-performance electrochemical deionization. Unlabelled Image • Rich N, P and S atoms doped electrode materials was obtained by self-assembling. • Highly cross-linked polymer can improve the ion removal and recycle. • Successful utilization in textile printing wastewater deionization [ABSTRACT FROM AUTHOR]

PAHs content distribution and TEQ values in pyrolysis liquid products of sludge from different sources • The effect of sludge source on the formation of the different molecule's PAHs was evident. • Most of 16 target PAHs were mainly distributed in pyrolysis oil and gas. • PAHs yielded most in the bio-oil produced by PDSS at 850℃, which was 51.25 mg kg−1. • The PAHs distribution in bio-oil was largely dependent on pyrolysis temperature. • The types and concentrations of PAHs formed in gas were less than that in bio-oil. This study investigated the presence and concentration of 16 U.S. EPA priority controlled PAHs in gas, bio-oil and residues from the pyrolysis of different sewage sludges. We studied the temperature as a key influential factor for the formation of 16 targets PAHs and the effect of sludge source on the distribution of different molecules' PAHs were analyzed. Results showed that most of the 16 PAHs were formed during sludge pyrolysis and mainly ended up in bio-oil and gas. The distribution of PAHs in bio-oil was mostly dependent on pyrolysis temperature. With the increase of pyrolysis temperature from 450℃ to 850℃, it has been observed an increase of PAHs concentration in the bio-oils as follows: 16 % (ISS), 1.3 % (food manufacture wastewater sludge, FSS), 194 % (printing and dyeing wastewater sludge, PDSS), 334 % (DSS). 2, 3 and 4-ring PAHs dominate, and their total mass proportion is over 70 %. In gas, the types and concentrations of PAHs were less than in bio-oil. PAHs yield in solid was very low, and a trace content of PAHs of 0.0161 mg kg−1 was detected from the solid after the pyrolysis of DSS, while PAHs in solid for ISS and FSS are even non-existent and would cause fewer environmental problems. [ABSTRACT FROM AUTHOR]

• Ag 3 PO 4 photocatalyst was prepared by precipitation method. • Photocatalytic degradation of MB dye was studied under visible light irradiation. • The decolorization of MB was mainly affected by operational conditions. • The mechanism of higher initial pH playing a positive role is elaborated. The Ag 3 PO 4 nanoparticles were facilely prepared via the liquid precipitation method, and the physical property, optical properties, crystalline and morphologic properties were explored using various techniques. The XRD and SEM results show Ag 3 PO 4 nanoparticles possessed the cubic phase structure and spheroid-like morphology with a particle size of about 300–500 nm. Spectra analysis results indicated that nanoparticles prepared had the same functional groups as Ag 3 PO 4 and can absorb visible light with wavelengths less than 530 nm. The photocatalytic degradation of a cationic azo dye methylthionine chloride (MB) using Ag 3 PO 4 as a photocatalyst in aqueous solution has been investigated under visible-light irradiation. The effects of different parameters on the photodegradation of MB were analyzed. During visible light photocatalytic degradation of MB in the water at different pH values by the Ag 3 PO 4 catalyst, the process was found along with a regular dependency between the degradation rate and adsorption capacity. Both the adsorption efficiency and degradation efficiency of MB on Ag 3 PO 4 increased with increasing initial solution pH value. Ag 3 PO 4 nanoparticles show excellent photocatalytic activity against cationic azo dye under visible-light irradiation and are expected to be effective as a promising visible-light photocatalyst for textile-dyeing wastewater remediation. [ABSTRACT FROM AUTHOR]

• Peculiar porous architecture with Ni supported Fe-Si-B glass is constructed. • Over 1000 % improvement in kinetic rate is achieved in degradation tests. • Structural electrocatalysis accelerates the degradation process. • The composite architecture bestows the material with high self-cleaning ability. • Superb durability of over 100 degradation cycles is revealed. Since the treatment of wastewater containing azo dye presents problems worldwide, it is important to seek effective materials and technology for the purification of wastewater containing azo dye. Fe-based metallic glasses have been identified as promising materials for the decomposition of dyeing wastewater due to their high chemical activity resulting from their amorphous structure. It is imperative to further improve their degradation performance, and especially their durability, for potential application in wastewater purification. Here, composite structures constructed of porous Ni and amorphous Fe 78 Si 9 B 13 powder with markedly enhanced degradation performance in Orange II solution were obtained by utilizing a magnet. Due to the favorable effects of structural electrocatalysis and high dispersity of the distinctive porous architecture in addition to its self-cleaning properties, the solid-liquid interface exhibited strong, continuous electrical and mass transport, and a compelling improvement in degradation performance was achieved. Based on degradation tests and spectrum analysis, the kinetic rate was improved over 11-fold. Moreover, ultra-high durability over 100 cycles was revealed in cycling tests. The results indicate that wastewater degradation performance can be greatly enhanced by properly combining Fe-based metallic glasses with porous material. [ABSTRACT FROM AUTHOR]

Accurate real-time determination of each dye in combination dyeing is critical to the control of dyeing process, which plays an important role in upgrading the dyeing techniques of textile. In this work, Raman spectroscopy was applied to dyeing baths containing multiple dye species of varying structures to quantitatively monitor the dyeing process of each individual dye. Quantitative models were successfully established by partial least squares (PLS) for all combinations of the nine commonly used reactive dyes studied. The correlation coefficients were greater than 0.99, the root mean squared errors of calibration (RMSEC) were less than 0.2650 and the root mean squared errors of prediction (RMSEP) were less than 0.1340, even for the three-component mixture of Reactive Red 239 (RR239), Reactive Yellow 176 (RY176) and Reactive Blue 194 (RB194), which are similar in structures. The model was shown to be valid in the presence of added electrolytes (sodium sulfates). Real-time adsorption monitoring based on the model revealed that the dyes interacted with one another and competed for active sites. The adsorption kinetics obtained by Raman analysis shed light on dye compatibility and could be used to guide the design of dyeing recipe and dyeing process for optimum color reproduction. In addition, in situ monitoring by Raman spectroscopy maybe integrated with real-time on line control of dyeing parameters for fully automated production of dyed fabrics. Unlabelled Image • Accurate real-time determination of each dye in combination dyeing was realized by Raman spectroscopy. • Use of chemometrics for quantitative analysis model development • To guide the design of dyeing recipe and solve the problem of continuous dyeing process in real time • Improving the utilization rate of dyes and reducing the discharge of dyeing wastewater • It is helpful to realize digital and intelligent development of dyeing process with multicomponent dyes. [ABSTRACT FROM AUTHOR]

Textile effluent is one of the major sources of land and water pollution due to the presence of dyes in addition to other contaminants. The lands receiving these toxic effluents have become deprived of a number of species of natural flora. Competency of indigenous bacterial strains to degrade the dyestuffs present in textile wastewater was evaluated. Decolourization by the bacterial strains was found to be 36%, 66% and 89% for B. cereus , B. thurningienis and B. licheniformis , respectively. The comparative analysis showed that COD reduced to 80% by B. cereus , 82% by B. thuringiensis and 93% by B. licheniformis whereas BOD reduced to 61% by B. cereus , 65% by B. thuringiensis and 69% by B. licheniformis. TS, TDS, TVS and TSS contents reduced to 34%, 89%, 21%, 9% by B. cereus , 36%, 98%, 30%, 41% by B. thuringiensis and 43%, 99%, 43% and 49% by B. licheniformis. Seed germination and growth of Triticum eastivum was used as an indicator to study the phytotoxic effects of textile mill effluents. Plants grown with treated effluent showed maximum growth of plumule and radical and such properties may be helpful to develop alternatives for the management of dyeing wastewater. Maximum tolerance index and minimum relative toxicity and percentage phytotoxicity was found with bioremidiated textile industrial effluent. This study showed the effectiveness of biological pretreatment involving appropriate microorganisms. Bioremediation, no doubt, is an inexpensive and environment friendly approach for eradication of toxic effects caused by dyes and ultimately the conservation of natural flora. Studies have shown toxic effects of textile discharges on plant growth and seed germination. Unfortunately knowing the facts about their serious environmental and health threats, the untreated mill waste water is allowed to flow in crop fields, river and drinking water. In this study, the bioassay used for mill effluent toxicity was established on assessing the changes in shoot and root elongation of Triticum aestivum using as a test plant. Significant reduction in shoot and root length was observed when plant grown in the presence of untreated effluent as compared to bioremidiated effluent and control after 7 days. Image 1 • Three Bacillus strains effectively decolorized the textile effluent by adsorption. • Bacilli highly reduced biological and chemical oxygen demand of effluent. • Total solid contents of effluent removed radically with all three Bacillus strains. • Plants grown with biological treated effluent showed maximum growth of plumule and radical. • Minimum percentage phytotoxicity was found with bioremediated industrial effluent. [ABSTRACT FROM AUTHOR]

The treatment of dye-containing wastewater generated from textile industries is still a challenge, and various technologies, including physical, chemical and biological ones have been used. In recent years, the ionizing radiation (usually including gamma ray generated by radionuclide, such as 60Co and 137Cs, and electron beam generated by electron accelerator) technology has received increasing attention for degrading refractory or toxic organic pollutants in wastewater because of its unique advantages, such as no chemical additives, fast reaction rate, strong degradation capacity, high efficiency, flexibility, controllability. Compared to the conventional wastewater treatment processes, ionizing radiation technology, as a disruptive wastewater treatment technology, is more efficient for the decolorization and degradation of dyes and the treatment of dye-containing wastewater. In this paper, the recent advances in the treatment of dye-containing wastewater by ionizing radiation, in particular by electron beam (EB) radiation were summarized and analyzed, focusing on the decolorization and degradation of various dyes. Firstly, the formation of various reactive species induced by radiation and their interactions with dye molecules, as well as the influencing factors on the removal efficiency of dyes were discussed. Secondly, the researches on the treating dye-containing wastewater by electron beam radiation technology were systematically reviewed. Then, the decolorization and degradation mechanisms by electron beam radiation were further discussed in detail. And the integrated processes that would contribute to the advancement of this technology in practical applications were examined. More importantly, the recent advances of electron beam radiation technology from laboratory to application were reviewed, especially successful operation of dye-containing wastewater treatment facilities in China. And eventually, current challenges, future research directions, and outlooks of electron beam radiation technology were proposed for further advancing this technology for the sustainable development of water resources. [Display omitted] • The treatment of dye-containing wastewater is still a challenge. • Advances in dye-containing wastewater treatment by EB were summarized and analyzed. • Mechanisms of dye decolorization and degradation by EB were discussed in detail. • EB is more efficient for the decolorization and degradation of dyes. • Challenges, future directions and outlooks of EB technology were proposed. [ABSTRACT FROM AUTHOR]

• Self-floating adsorbents can reach surface solid-liquid separation spontaneously. • The two-step synthesis process of SFA is simple and efficient. • Single-layer grafting allows the adsorption to reach equilibrium within 10 min. • Concentrate low concentration dyes to industrially usable levels by desorb method. In the case of a sharp increase in the price of dyes, the dyes concentration of in wastewater is important for environmental protection and industrial costs reduction. In this study, we grafted single-layer amino groups onto the surface of the hollow glass microspheres by a two-step simple synthesis, and the anionic dyes adsorption process reaches equilibrium within 10 min. The as-synthesized adsorbent has self-floating ability to achieve high-efficiency surface solid-liquid separation with water. SEM, EDS, S BET , FT-IR, XPS, TGA characterizations results demonstrated the successful grafting of amino groups and the important role of the pretreatment process in the two-step synthesis. The results of adsorption isotherms and kinetics show the adsorption process belongs to single-layer adsorption with equal adsorption sites, and the adsorption capacities for acid orange 7 and amaranth reach 428.99 mg g−1 and 145.62 mg g−1, respectively. Regeneration of the adsorbent and concentration of the dye solutions can be achieved by dispersing the separated adsorbent in alkaline solution, the maximum concentrated concentration of acid orange 7 and amaranth was 6321.57 mg L−1 and 2431.84 mg L−1, respectively. This study provides new insights for the solid-liquid separation of water treatment agents and the resource regenerating of dyeing wastewater. [ABSTRACT FROM AUTHOR]

• Controllable and stable physical hydrogel based on chitosan was prepared. • Compositing of polyacrylate improved the swelling and adsorption properties. • Graphene oxide enhanced mechanical and adsorption properties of the hydrogel. • The products showed properties of adjustable polyampholyte hydrogel. • The composite hydrogel could simultaneously adsorb cationic and anionic dye. In the current study, a novel CTS/PAA/GO composite polyampholyte physical hydrogel was prepared by the SD-A-SGT method to achieve desired adsorption properties for printing and dyeing wastewater treatment. The hydrogels exhibited controllable and stable structure. The linear PAA significantly improved the swelling and adsorption properties of the hydrogel, and the composition of GO enhanced its mechanical and adsorption properties. The batch adsorption experiments revealed the ability to simultaneously absorb the cationic model dye, MB, and anionic model dye, FY3, with the similar equilibrium adsorption capacities of 296.5±31.7 mg·g−1 and 280.3±23.9 mg·g−1, respectively. The factors affecting the dye adsorption performance, including the hydrogel composition, initial dye concentration and dye solution pH, were investigated. The dye adsorption kinetics was studied and the adsorption mechanisms were proposed. The unique structure and properties of the hydrogel make it a great candidate adsorbent for wastewater treatments. [ABSTRACT FROM AUTHOR]

• A novel electrospun photocatalyst membrane was fabricated for regeneration. • Membrane hydrophobicity was heightened by BiOBr/Ag photocatalyst coating. • Ag nanoparticles promote electron separation efficiency, reducing band gap energy. • Employed optical coherence tomography to monitor foulant growth in real-time. • Recovery efficiency of over 90% achieved during testing under visible light. In this study, an innovative electrospun photocatalyst self-cleaning BiOBr/Ag membrane is introduced for the MD treatment of dyeing wastewater coupled with post-MD UV and visible light exposure for fouled membrane regeneration. The E-BiOBr/Ag membrane was fabricated by successfully coating an electrospun membrane with BiOBr/Ag catalyst particles using electrospray technology, with the goal to achieve higher hydrophobicity and the reproducible property. Along with the E-BiOBr/Ag membrane, two commercial polyvinylidene difluoride (PVDF) and polytetrafluoroethylene (PTFE) membranes were tested for comparison. The fouling processes on all three membranes were monitored in real-time using optical coherence tomography (OCT). The coating of BiOBr/Ag particles on the E-BiOBr/Ag membrane's surface accelerated dye foulant degradation through the electron-holes' strong oxidization capacity when exposed to UV. Meanwhile, after Ag nanoparticles were coated on the BiOBr photocatalyst by UV deposition method, not only improved the efficiency of electron separation and transfer but also lessened the electron recombination phenomenon effectively. Correspondingly, compared to the two commercial membranes, the BiOBr/Ag photocatalyst membrane achieved significant improvements in the recovery efficiencies of the water contact angle (95.6%) and water flux (92.2%) under UV illumination, pointing to its potential for fouled membrane regeneration. In addition, the deposition of Ag on BiOBr as cocatalyst enhanced the visible light harvesting. Finally, the BiOBr/Ag photocatalyst membrane maintained good flux recovery and dye rejection (99.9%) over a 5-cycle MD test coupled with visible light exposure, suggesting the application of the novel self-cleaning photocatalyst membrane as a potential alternative for upscaling MD technology to the industrial level. [ABSTRACT FROM AUTHOR]

• Polyethylenimine-functionalized magnetic carbon nanotubes were successfully prepared. • The prepared adsorbent possessed excellent adsorption performances for Alizarin Red S. • The PEI@MCNTs can be used as an efficient adsorbent for practical application. • The study presents a promising strategy for the preparation of dyes adsorbent. Alizarin Red S (ARS) has been extensively used in the dyeing industry. In order to effectively remove the ARS form dyeing wastewater, polyethyleneimine (PEI)-functionalized magnetic carbon nanotubes (PEI@MCNTs) adsorbent was successfully prepared and its adsorption performances were also investigated in detail. The PEI@MCNTs could efficiently remove the ARS from acidic aqueous solution (pH ≤ 6.0) within 40 min under room temperature. Benefiting from a large number of adsorption sites and multiple interactions, PEI@MCNTs possessed high selectivity towards ARS with spontaneous adsorption process. The maximum adsorption capacity of PEI@MCNTs for ARS was 196.08 mg g−1 obtained from Langmuir isotherm, higher than that of available conventional adsorbents. Moreover, the PEI@MCNTs could be easily collected by an external magnet, and then effectively regenerated through 10 mM NaOH solution. The prepared PEI@MCNTs could be considered as the promising adsorbent for the removal of anthraquinone dyes in large-scale wastewater treatment. [ABSTRACT FROM AUTHOR]

Rapid charge transfer in various piezoelectric semiconductors is usually limited, which has thus hardly achieved a higher mechanochemical potential elicited by macroscopic polarization for advanced oxidation processes. Here we propose a piezoelectric ZnO/BaTiO 3 heterostructure with an elevated macroscopic polarization under ultrasonic activation and, therefore, should be amenable to facilitate photoexcited electron-hole pairs with more efficient separation and transfer; that is, ZnO/BaTiO 3 heterostructures have an enhanced piezophototronic effect. Under excitations of concurrent ultrasound at ultrasonic power of 120 W and simulated sunlight at light intensity of 100 mW cm−2 irradiation, the catalytic oxidation capability to dyeing wastewater degradation with ZnO/BaTiO 3 is dramatically increased, and its oxidation reaction rate constant can be up to 1.20 × 10−1 min−1, which is 1.50 and 2.00 times that of BaTiO 3 and ZnO, respectively. In contrast, ultrasonic agitation or simulated sunlight irradiation of ZnO/BaTiO 3 results in an oxidation reaction rate constant of 3.46 × 10−2 or 5.60 × 10−2 min−1, correspondingly, which are both lower than the piezophototronic effect triggered. Additionally, the finite element simulation shows that the as-obtained ZnO/BaTiO 3 creates a piezoelectric potential difference of 414.40 mV, which is higher than that of as-obtained BaTiO 3 (409.50 mV) and ZnO (33.00 mV). This work will provide references for understanding the correlation between macroscopic polarization and catalytic oxidation processes, and also contribute to the development and applications of multi-energy harvesting piezoelectric materials. Specific ultrasound excitation of ZnO/BaTiO 3 heterostructures resulted in a piezoelectric potential difference of 414.40 mV, which is much higher than pure BaTiO 3 and ZnO. Consequently, the photoexcited electron–hole pairs can be easily separated and transfer in ZnO/BaTiO 3 , thus creating more free radicals to accelerate piezophotocatalytic oxidation processes in aqueous solution. Image 1 • ZnO/BaTiO 3 was prepared by combining solvothermal and impregnation sintering. • ZnO/BaTiO 3 has a higher piezoelectric potential difference than BaTiO 3 and ZnO. • The flat band potential of ZnO/BaTiO 3 is more negative than BaTiO 3 and ZnO. • ZnO/BaTiO 3 has superior catalytic oxidations initiated by piezophototronic effect. • ZnO/BaTiO 3 can efficiently utilize ultrasound and light irradiation simultaneously. [ABSTRACT FROM AUTHOR]

Graphene-based hydrogels (GH) have exhibited prominent performances in wastewater treatment. Herein, Special-shaped ZnO tetrapods and TiO 2 nanosheets were introduced to the preparation of GH via a one-step hydrothermal reduction method. The ZnO-GH and TiO 2 -GH composite hydrogel with a uniform 3D network structure and good mechanical properties can be used as an adsorbent for printing and dyeing wastewater. The optimum doping amount of ZnO and TiO 2 in the composite hydrogel and the adsorption regularity to rhodamine B (RhB) with different concentrations were discussed. The cyclic adsorption performance and adsorption kinetics were briefly discussed. When the doping ratio of ZnO to graphene oxide (GO) is 5:8, ZnO-GH has the best adsorption rate, which is 71.7%. The best degradation rate appears at a ZnO doping ratio of 1:2, which also shows the best total removal rate of RhB of approximately 82.20%. When the doping ratio of TiO 2 to GO is 3:4, the photocatalytic degradation rate is 30.3%, and the total removal rate of RhB reaches 99.1%, which indicates that RhB can be almost completely removed by TiO 2 -GH through adsorption and degradation. After five cycles, the adsorption capacity of ZnO-GH and TiO 2 -GH for the low RhB concentration is still good. The addition of ZnO and TiO 2 improves not only the adsorption and degradation properties of the composite hydrogel but also its recycling performance as a result of the increase in mechanical stability. [ABSTRACT FROM AUTHOR]

Reactive dyeing of cotton generates a great deal of coloring wastewater containing residual dyes, electrolyte, alkali, and other auxiliaries. Especially for the effluent from the first/initial spent dyeing bath, it may be comprised of as high as 60% of the initial dye dosed, 30–90 g/L of sodium chloride or sodium sulfate, and plenty of sodium carbonate, making it to be the most contaminative effluent among the entire reactive dyeing process. This paper presents a new alternative to regenerate the waste effluent from the first spent dyeing bath through catalytic ozonation with novel catalysts for reuse of the effluent in successive dyeing. Two novel ozonation catalysts, mesoporous carbon aerogel and its supported cobalt oxide nanoparticles, were successfully prepared and used in catalytic degradation of residual dyes in waste effluents with ozone. Degradation efficiency was determined by both decolorization and chemical oxygen demand removal. The result showed novel catalysts could improve both of these two targets. For chemical oxygen demand removal, carbon aerogel supported cobalt oxide strikingly enhanced the efficiency by 30% on the whole comparing to ozonation alone (approximately 50%) without the catalyst. Waste effluents after catalytic ozonation were thereafter reused in successive dyeing in the same process. It has been validated that the waste effluent was successfully regenerated and can be additionally reused twice without sacrificing fabric quality, which cannot be realized in ozonation alone. Color difference of the fabric dyed with the regenerated effluent was within the acceptable tolerance, and excellent levelness and equal colorfastness had also been achieved. This is probably the first study to investigate the feasibility of regenerating highly polluting dyeing effluents for reuse by catalytic ozonation with carbon aerogel materials. With novel catalysts, it could be speculated that catalytic ozonation is a promising technology for in-situ regeneration of waste effluents in textile dyeing plant for reuse. [ABSTRACT FROM AUTHOR]

The textile and dyeing industries are major sources of environmental water pollution all over the world. The textile wastewater effluents discharged into rivers often appear dark red-purple in color due to azo dyes, which can be transformed into carcinogenic aromatic amines. The chemicals used in dyeing are not readily degraded in nature and thus precipitate in river sediment. However, little is known about how dyeing chemicals affect river sediment and river water or how long they persist because they are difficult to monitor. To assess undetectable dyes and byproducts in river sediments, we evaluated the potential of river sediment bacteria to degrade dyes and aromatic amines. We describe the natural remediation of river sediment long-contaminated by textile dyeing effluent. After cessation of wastewater discharge, the dye-degradation potential decreased, and the aromatic amine–degradation potential increased initially and then declined over time. The changes in degradation potential were consistent with changes in the sediment bacterial community. The transition occurred on the order of years. Our data strongly suggest that dyes remained in the river sediment and that aromatic amines were produced even in transparent- and no longer colored–river water, but these chemicals were degraded by the changing sediment bacteria. Time-course monitoring of the degradation activities of key bacteria thus enables assessment of the fate of dye pollutants in river sediments. [ABSTRACT FROM AUTHOR]

Abstract: We determined the effectiveness of nano zerovalent iron (NZVI) to treat Reactive Black 5 (RB5), Reactive Red 198 (RR 198), a mix of both dyes, and wastewater from the textile dyeing industry. Experimental variables, such as NZVI dosage, initial dye concentration, solution pH, catalyst, and Na salt, were investigated. The degradation kinetic rate constants of both dyes increased with the increase of NZVI dosage, but decreased when initial concentrations were higher. Lowering the pH from 9 to 3 increased the kinetic rates of destruction of RB5 and RR198 by NZVI. Adding Pd and TiO2/light to the surface of NZVI enhanced the kinetic rates of removal of RB5 and RR198. Increasing the NaCl concentration from 0.1% (w/v) to 1% (w/v) also improved the kinetic removal rates of RB5 and RR198. The UV spectra showed that complete degradation of authentic wastewater by NZVI occurred within 3h. This study also determined the efficiency of dye removal using NZVI supported on sand, silica oxide and biological sludge. The removal efficiencies of both RB5 and RR198 were higher than 70% within 90min in every NZVI/support. In column experiment, decolorization efficiencies remained more than 80% up to 3800mL and 3,000mL of effluent volumes for RB5 and RR198, respectively. [ABSTRACT FROM AUTHOR]

Abstract: This paper reviews the application of polymeric nanofiltration membranes (NF) in the specific waste stream in the textile industry, which typically generates large volumes of wastewater containing complex contaminants from its daily operation. It is necessary that as much of this waste as possible is recycled instead of being disposed of in landfill sites. Most of the conventional technologies seem unable to provide sufficient treatment for the effluents. Therefore, it is generally accepted that NF membranes offer solutions for the problem. Of these NF membranes, the thin-film composite nanofiltration (TFC–NF) membrane is the most widely used by researchers in their studies. The effects of the manufacturing conditions of TFC–NF are discussed to provide valuable information for those who are going to choose NF membranes in textile wastewater treatment. The preliminary performances of commercial NF membranes have been examined in terms of dye rejection, salt rejection, permeate flux and COD rejection. Some of the commercial membranes achieved maximum separation of dye and salts while some achieved higher flux. This is because of the large variability of the parameters of textile wastewater and the NF membranes chosen. Due to the scarcity of published papers covering the transport model that is specifically suitable for textile coloured wastewater, a brief review of transport models of NF membranes with the presence of the dyes and salts is given. Membrane fouling mechanisms and methods to control fouling are also reviewed. Future directions in NF membrane research are also discussed to further expand research and development related to textile wastewater treatment. [Copyright &y& Elsevier]

Abstract: This paper presents the determination of the best pre-treatment method to nanofiltration (NF) for the recovery of print dyeing wastewaters (PDW) of the carpet manufacturing industry. Chemical precipitation (CP) with optimum alum (Al2SO4.18H2O) dose was chosen among five alternatives; 1) Dead-end microfiltration (MF), 2) CP with optimum coagulant dose, 3) CP with low coagulant dose and polyelectrolyte aid, 4) CP with low coagulant dose followed by MF, 5) CP with high coagulant dose followed by ultrafiltration (UF). In the selected process, an optimum alum dose of 150 mg/L provided color and turbidity removal efficiencies of >90%. The effectiveness of the selected pre-treatment method for flux control in post NF was also tested. Perfect rejection of COD, color and turbidity was achieved in NF, accompanied by a stable flux decline of around 22%. Moreover, the flux decline was mainly due to concentration polarization rather than fouling, indicating reversible flux decline. [Copyright &y& Elsevier]

Abstract: Electrocoagulation (EC) is one of the most effective techniques to remove color and organic pollutants from wastewater, which reduces the sludge generation. In this paper, electrocoagulation has been used for the removal of color from solutions containing C. I. Basic Red 46 (BR46) and C. I. Basic Blue 3 (BB3). These dyes are used in the wool and blanket factories for fiber dyeing. The effect of operational parameters such as current density, initial pH of the solution, time of electrolysis, initial dye concentration and solution conductivity were studied in an attempt to reach higher removal efficiency. The findings in this study shows that an increase in the current density up to 60–80Am−2 enhanced the color removal efficiency, the electrolysis time was 5min and the range of pH was determined between 5.5 and 8.5 for two mentioned dye solutions. It was found that for, the initial concentration of dye in solutions should not be higher than 80mgl−1 in order to achieve a high color removal percentage. The optimum conductivity was found to be 8mScm−1, which was adjusted using proper amount of NaCl with the dye concentration of 50mgl−1. Electrical energy consumption in the above conditions for the decolorization of the dye solutions containing BR46 and BB3 were 4.70kWh(kgdye removed)−1 and 7.57kWh(kgdye removed)−1, respectively. Also, during the EC process under the optimized conditions, the COD decreased by more than 75% and 99% in dye solutions containing BB3 and BR46, respectively. [Copyright &y& Elsevier]

The study prepared a self-adaption adsorbent that was capable of removing anionic dye over a wide range of pH value and revealed its essential adsorption mechanism to the conventional dyes as target pollutants. Through a cross-linking/embedding method, MgO particles were successfully combined with magnetic substances and Chitosan, which created a novel magnetic adsorbent (named as MgO-MCS) that could be used to efficiently remove anionic dyes by self-adjusting its surface charge. A series of characterization techniques and adsorption experiments were conducted to reveal the properties and the adsorption mechanisms, whose results showed that MgO-MCS had a better adsorption effect, and wider application range than that of magnetic Chitosan (MCS). The enhancement of adsorption was attributed to the formed more micropores and mesopores on the surface of MgO-MCS, and the essential mechanism was mainly caused by the combined effects of van der Waals force, electrostatic interaction and hydrogen bond. [Display omitted] • MgO-MCS as a novel adsorbent was successfully prepared. • The adsorbent showed high adsorption capacity to various anionic dyes. • The adsorbent showed a self-adaptation ability to the pH of surrounding solution. • MgO-MCS exhibited magnetic separation capability. [ABSTRACT FROM AUTHOR]

The film photocatalyst is easily recycled and has attracted the widely research interesting. Here the ferroelectric Hf 0.5 Zr 0 · 5 O 2 (HZO) thin film synthesized through the atomic layer deposition (ALD) method is used as a photocatalyst for the rhodamine B (RhB) dye decomposition under visible light irradiation. The photocatalytic RhB dye decomposition performances with or without an external magnetic field excitation provided by a commercial NdFeB magnet are experimentally characterized. With the increasing of the external direct-current (DC) magnetic field from 0 to 3000 Gs, the photocatalytic RhB dye decomposition ratio by HZO film obviously increases from 87.20 % to 98.17 %, which is attributed to the enhanced separation of the photo-induced positive and negative carrier due to the magnetic Lorentz effect. The magnetically-induced enhancement of photocatalysis in the ferroelectric HZO film, provides a method with these advantages of simple external excitation method, remarkable promotion effect and friendly-environment to enhance the dye decomposition ratio, and is potential in the practical application of photocatalytic dye wastewater treatment through harvesting the clean solar energy in future. [ABSTRACT FROM AUTHOR]