A critical review on textile wastewater treatments: Possible approaches

Preparation of Sulfonated Poly(arylene ether nitrile)-Based Adsorbent as a Highly Selective and Efficient Adsorbent for Cationic Dyes

In this work, a highly selective and efficient polymer adsorbent inspired by a water-soluble sulfonated poly(arylene ether nitrile) (SPEN) was successfully synthesized. Due to the distinct structure of functional carboxyl, sulfonic acid and rigid benzene rings, a facile aluminium (III) ions crosslinking method was employed to fabricate the SPEN-based adsorbents (SPEN-Al). Among the three adsorbents, SPEN-Al-2 exhibited superior adsorption capacities with uniform morphology. Subsequently, the SPEN-Al-2 was selected as the adsorbent for three cationic dyes (rhodamine B (Rh B), neutral red (NR), methylene blue (MB)) and three anionic dyes (orange G (OG), methyl orange (MO), acid fuchsin (AF)), respectively, demonstrating that the adsorbent possessing excellent selectivity toward cationic dyes. Moreover, the dye's adsorption selectivity of SPEN-Al-2 was further certificated in a binary cationic-anionic dyes mixtures (MB/OG and MB/MO) system. Taking MB as a dye model, a series of factors (contact time, concentration, temperature and pH) and adsorption models were systematically investigated in dye adsorption experiments. Results indicated that the adsorption was endothermic and the maximum adsorption capacity of SPEN-Al-2 could reach up to 877.5 mg/g; pseudo-second-model and Langmuir model were fitted to the adsorption kinetics and equilibrium isotherm, respectively, manifesting that SPEN-Al adsorbent was promising in the dyes removing field.

Decolorization and detoxification of textile wastewaters by recombinant Myceliophthora thermophila and Trametes trogii laccases

Laccases are multi-copper oxidoreductases with broad biotechnological applications. Here, we report detailed biochemical characterization of purified recombinant laccases originating from Myceliophthora thermophila (MtL) and Trametes trogii (TtL). We identified optimal conditions for decolorization of commercial dyes and textile wastewater samples. We also tested the toxicity of decolorized wastewater samples using human peripheral blood mononuclear cells. MtL and TtL were expressed in Saccharomyces cerevisiae, and secreted enzymes were purified by consecutive hydrophobic and gel chromatography. The molecular masses of TtL (~ 65 kDa) and MtL (> 100 kDa) suggested glycosylation of the recombinant enzymes. Deglycosylation of MtL and TtL led to 25% and 10% decreases in activity, respectively. In a thermal stability assay, TtL retained 61% and MtL 86% of the initial activity at 40 °C. While TtL retained roughly 50% activity at 60 °C, MtL lost stability at temperatures higher than 40 °C. MtL and TtL preferred syringaldazine as a substrate, and the catalytic efficiencies for ABTS oxidation were 7.5 times lower than for syringaldazine oxidation. In the presence of the mediator HBT, purified TtL almost completely decolorized dyes within 30 min and substantially decolorized wastewater samples from a textile factory (up to 74%) within 20 h. However, products of TtL-catalyzed decolorization were more toxic than MtL-decolorized products, which were almost completely detoxified.

Simultaneous elimination of Malachite Green, Rhodamine B and Cresol Red from aqueous sample with Sistan sand, optimized by Taguchi L16 and Plackett-Burman experiment design methods

The purpose of this study was to investigate the feasibility of simultaneous optimization and removal of dyes, Malachite green (MG), Rhodamine B (RhB) and Cresol Red (CR) from aqueous solutions by using Sistan sand as an extremely low cost adsorbent. Factors affecting adsorption of the analytes on the sorbent were investigated experimentally and by using Taguchi and Plackett–Burman experimental design methods. In most cases, the results of these two models were in agreement with each other and with experimental data obtained. Taguchi method was capable to predict results with accuracies better than 97.89%, 95.43%, and 97.79% for MG, RhB, and CR, respectively. Under the optimum conditions, the sorbent could remove simultaneously more than 83% of the dyes with the amount of adsorbed dyes of 0.132, 0.109, and 0.120 mg g⁻¹ for MG, RhB and CR on sand, respectively. Kinetic studies showed that pseudo second order is the best model of adsorption for all analytes. Thermodynamic parameters revealed that this process is spontaneous and endothermic.

Polyethylene glycol-doped BiZn2VO6 as a high-efficiency solar-light-activated photocatalyst with substantial durability toward photodegradation of organic contaminations

In this study, we focus on a simple, low-priced, and mild condition hydrothermal route to construct BiZn₂VO₆ nanocompounds (NCs) as a novel photocatalyst with strong solar light absorption ability for environmental purification using solar energy. NCs were further doped with polyethylene glycol (PEG) to improve their photocatalytic efficiency for photodegradation processes through inhibition of fast charge carrier recombination rates and higher charge separation efficiency. Surface morphology, phase structure, optical characteristics, and band structure of the as-prepared samples were analyzed using XRD, EDX, XPS, SEM, UV-vis spectroscopy, CL, and BET techniques. PEG-doped BiZn₂VO₆ NCs were applied as effective materials to degrade various kinds of organic pollutants including cationic and anionic types, and these NCs exhibited excellent photocatalytic efficiency as compared to traditional photocatalysts. In particular, the PEG-doped BiZn₂VO₆ (0.10% w/v) photocatalyst exhibited highly enhanced photocatalytic performance with improvements of about 46.4, 28.3, and 7.23 folds compared with PEG-doped ZnO nanorods (NRs), pristine BiVO₄, and BiZn₂VO₆ samples, respectively, for the decomposition of congo red (CR) dye. After 40 minutes of sunlight irradiation, 97.4% of CR was decomposed. In this study, scavenging experiments indicated that both hydroxyl radicals and holes play dominant roles in CR photodegradation under simulated solar light irradiation. Meanwhile, the optimal photocatalyst demonstrated good reproducibility and stability for successive cycles of photocatalysis.

Application of response surface methodology in physicochemical removal of dyes from wastewater: A critical review

Response surface methodology (RSM) is a powerful tool in designing the experiments and optimizing different environmental processes. However, when it comes to wastewater treatment and specifically dye-containing wastewater, two questions arise; "Is RSM being used correctly?" and "Are all capabilities of RSM being exploited properly?". The current review paper aims to answer these questions by scrutinizing different physicochemical processes that utilized RSM in dye removal. The literature that applied RSM to adsorption, advanced oxidation processes, coagulation/flocculation and electrocoagulation processes were critically reviewed in this paper. The common errors in applying RSM to physicochemical removal of dyes are identified and some suggestions are made for future studies.

A review on geopolymers as emerging materials for the adsorption of heavy metals and dyes

The world water resources are contaminated due to discharge of a large number of pollutants from industrial and domestic sources. A variety of a single and multiple units of physical, chemical, and biological processes are employed for pollutants removal from wastewater. Adsorption is the most widely utilized process due to high efficiency, simple procedure and cost effectiveness. This paper reviews the research work carried out on the use of geopolymer materials for the adsorption of heavy metals and dyes. Geopolymers possess good surface properties, heterogeneous microstructure and amorphous structure. The performance of geopolymers in the removal of heavy metals and dyes is reported comparable to other materials. The pseudo-second order kinetics and Langmuir isotherm models mostly fit to the adsorption data suggesting homogeneous distribution of adsorption sites with the formation of monolayer adsorbate on the surface of geopolymers. Adsorption of heavy metals and dyes onto geopolymers is spontaneous, endothermic and entropy driven process. Future research should focus on the enhancement of geopolymer performance, testing on pollutants other than heavy metals and dyes, and verification on real wastewater in continuous operation.

Electrochemical degradation of Mordant Blue 13 azo dye using boron-doped diamond and dimensionally stable anodes: influence of experimental parameters and water matrix

In this work, the electrooxidation as environmentally clean technology has been studied to the degradation of Mordant Blue 13 azo dye (MB13) using boron-doped diamond (p-Si/BDD) and oxide ruthenium titanium (Ti/Ru_0.3Ti_0.7O₂ (DSA)) anodes in various water matrices: distilled water (DW), hot tap water (HTW), and simulated wastewaters with (SWS) and without surfactant (SW). The influence of experimental parameters, such as current density, initial dye concentration, electrolysis time/specific charge, and pH on the MB13 degradation rate, current efficiency, and energy consumption, has been determined. The enhanced rate of both color and chemical oxygen demand (COD) removal in sulfate aqueous solutions with BDD was observed, which indicates that sulfate (SO₄^-•) radicals along with ^•OH ones might be responsible for the degradation process. The MB13 decolorization process obeyed a pseudo-first-order reaction kinetics with the apparent rate constant from 7.36 × 10^-2 min^-1 to 4.39 × 10^-1 min^-1 for BDD and from 9.2 × 10^-3 min^-1 to 2.11 × 10^-2 min^-1 for DSA depending on the electrolysis conditions. The effect of water matrix on the decolorization and COD removal efficiency has been evaluated. Inorganic ions, mordant salt, and surfactant contained in simulated effluents decelerated the COD decay compared to DW and HTW for the both anodes; meanwhile, they differently affected the discoloration process. A comparison of the specific energy consumption for each electrocatalytic material under different experiment conditions has been made. The BDD electrode was more efficient than the DSA to oxidize the MB13 dye in all kinds of water.

Concentrate minimization and water recovery enhancement using pellet precipitator in a reverse osmosis process treating textile wastewater

Industrial wastewater reuse together with zero or near zero liquid discharges have been a growing trend due to the requirement of sustainable water management mandated by water scarcity and tightening discharge regulations. Studies have been conducted on the reclamation of textile industry wastewater using RO processes. However a lot of scientific attention has been drawn upon limiting the amount of concentrate generated from RO processes, which depends on the concentrations of scale forming ions in the concentrate stream. Hence, this study aims at investigating the applicability of an ultra-filtration (UF) membrane integrated pellet reactor to remove scale forming ions, i.e. Ca²⁺, Mg²⁺ and Si from the concentrate of a pilot-scale textile industry RO process, for the first time in the literature. The resulting effluent was further tested in a secondary RO process to decrease concentrate volume and increase total water recovery. The pellet reactor operated at an extremely low hydraulic retention time of 0.1 h removed scale forming ions, i.e. Ca²⁺, Mg²⁺, with 90-95% efficiency, which improved the secondary RO process performance up to 92-94% overall water recovery, i.e. near zero liquid discharge was reached. Ozonation of the concentrate partially removed COD and color, which further improved the secondary RO filtration performance.

Treatment of industrial dyeing wastewater with a pilot-scale strengthened circulation anaerobic reactor

We developed a pilot-scale strengthened circulation anaerobic (SCA) reactor (with an effective volume of 27 m³) and applied to the treatment of industrial textile wastewater. The treatment performance and the working mechanism were studied systematically and the key operational parameters were identified. The results demonstrated that a stable and excellent chemical oxygen demand removal efficiency of 62.7% and a maximum chromaticity removal efficiency of 73.5% were obtained at an optimal reflux ratio of 4. Interestingly, the bio-degradability was evidently improved after the SCA reactor treatment. The high throughput sequencing analysis indicated that the diversity of the bacteria or archaebacteria before the treatment was slightly higher than that after the treatment, which may be attributed to the production of certain toxic intermediates and/or characteristic pollutants during the treatment. Enzyme activity test and COD removal show that numerous microorganisms still maintained active in the anaerobic granular sludge even in a severe environment.

Forward Osmosis Application in Manufacturing Industries: A Short Review

Forward osmosis (FO) is a membrane technology that uses the osmotic pressure difference to treat two fluids at a time giving the opportunity for an energy-efficient water and wastewater treatment. Various applications are possible; one of them is the application in industrial water management. In this review paper, the basic principle of FO is explained and the state-of-the-art regarding FO application in manufacturing industries is described. Examples of FO application were found for food and beverage industry, chemical industry, pharmaceutical industry, coal processing, micro algae cultivation, textile industry, pulp and paper industry, electronic industry, and car manufacturing. FO publications were also found about heavy metal elimination and cooling water treatment. However, so far FO was applied in lab-scale experiments only. The up-scaling on pilot- or full-scale will be the essential next step. Long-term fouling behavior, membrane cleaning methods, and operation procedures are essential points that need to be further investigated. Moreover, energetic and economic evaluations need to be performed before full-scale FO can be implemented in industries.

Textile Dye Decolorizing Synechococcus PCC7942 Engineered With CotA Laccase

Cyanobacteria are prokaryotic phototrophs capable of achieving high cellular densities with minimal inputs. These prokaryotic organisms can grow using sunlight as energy source and carbon dioxide as carbon source what makes them promising candidates as microbial cell factories for the production of numerous compounds such as chemicals, fuels, or biocatalysts. In this study, we have successfully designed and constructed using synthetic biology approach two recombinant strains of Synechococcus elongatus PCC7942 for heterologous expression of the industrially relevant Bacillus subtilis CotA laccase. One of the strains (PCC7942-NSI-CotA) was constructed through integration of the laccase gene into neutral site I of the cyanobacterial genome whilst the other (PCC7942-NSII-CotA) targeted neutral site II of the genome. Of the two strains the one with CotA laccase integrated in neutral site II (PCC7942-NSII-CotA) was superior in terms of growth rate and enzymatic activity toward typical laccase substrates: ABTS [2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonate)] and syringaldazine. That may suggest that two of the traditionally used neutral sites of S. elongatus PCC7942 are not equally suitable for the expression of certain transgenes. The PCC7942-NSII-CotA produced protein was capable of decolourising three classes of dyes namely: anthraquinonic-, azo-, and indigoid-type over 7 days of incubation making the strain a potentially useful microbial cell factory for the production of broad-spectrum biodegradation agent. Interestingly, presence of additional synthetic redox mediator ABTS had no effect on the degradation of these dyes.

Graphitic carbon nitride nanosheets anchored with BiOBr and carbon dots: Exceptional visible-light-driven photocatalytic performances for oxidation and reduction reactions

The aim of this work is the fabrication of very efficient visible-light-driven photocatalysts through anchoring carbon dots and BiOBr over nanosheets of graphitic carbon nitride. Hence, a series of g-C₃N₄ nanosheets/Carbon dots/BiOBr (denoted as CNNS/CDs/BiOBr) nanocomposites with different amounts of BiOBr were synthesized by refluxing route. The resultant photocatalysts were characterized by XRD, EDX, SEM, TEM, HRTEM, AFM, XPS, FT-IR, UV-vis DRS, TGA, BET, and PL instruments. Among the photocatalysts, the CNNS/CDs/BiOBr (20%) nanocomposite exhibited the highest photocatalytic performance for degradations of RhB, MB, and MO under visible light, which is about 129, 29.8, and 20.5 times as superior as the CN powder, respectively. Also, photoreduction of Cr(VI) to Cr(III) over the ternary nanocomposite with 20% of BiOBr showed high photoactivity, which was 21.7-folds higher than that of the pristine CN. Reactive species trapping experiments revealed that superoxide anion radicals and hydroxyl radicals played significant role in degradation reaction of RhB. The utilized photocatalyst was recycled with negligible loss in the activity, which is important in photocatalytic processes. Finally, by studying the electrochemical behavior, the band alignments of the semiconductors were obtained and the preliminary mechanism was suggested as a direct Z-scheme system for the enhanced interfacial charge separation and transfer, which leads to the exceptional photocatalytic performance.

Degradation of organic dyes by a new heterogeneous Fenton reagent - Fe2GeS4 nanoparticle

The heterogeneous Fenton system has become the hotspot in the decontamination field due to its effective degradation performance with a wide pH range. Based on the unstable chemical properties of pyrite, in this article, Fe₂GeS₄ nanoparticles with better thermodynamic stability were prepared by vacuum sintering and high energy ball milling and its potential as Fenton reagent was investigated for the first time. Three determinants of the heterogeneous Fenton system including the iron source, hydrogen peroxide, pH and the degradation mechanism were investigated. The catalyst dosage of 0.3 g/L, initial H₂O₂ concentration in the Fenton system of 50 m mol/L and pH of 7 were chosen as the best operational conditions. An almost complete degradation was achieved within 5 min for methylene blue and rhodamine b while 10 min for methyl orange. The total organic carbon removal efficiencies of Fe₂GeS₄ heterogeneous Fenton system for methylene blue, methyl orange and rhodamine b in 10 min were 56.3%, 66.2% and 74.2%, respectively. It's found that the degradation ability could be attributed to a heterogeneous catalysis occurring at the Fe₂GeS₄ surface together with a homogeneous catalysis in the aqueous phase by the dissolved iron ions.

Functional graphene oxide membrane preparation for organics/inorganic salts mixture separation aiming at advanced treatment of refractory wastewater

Some refractory organic matters or soluble microbial products remained in the effluents of refractory organic wastewater after biological secondary treatment and need an advanced treatment before final disposal. Graphene oxide (GO) was known to have potential to be the next generation membrane material. The functional organics/inorganic salts separation GO membrane preparation and application in wastewater advanced treatment could reduce energy or chemicals consumption and avoid organics/inorganic salts mixed concentrate waste problems after nanofiltration or reverse osmosis. In this study, we developed a novelty GO membrane aiming at advanced purification of organic matters in the secondary effluents of refractory organic wastewater and avoiding the organics/inorganic salts mixed concentrate waste problem. The influence of preparation conditions including pore size of support membrane, the number of GO layers and the applied pressure was investigated. It was found that for organics/inorganic salts mixture separation membrane preparation, the rejection and flux would achieve balance for the support membrane at a pore size of ~0.1μm and the number of GO layers of has an optimization value (~10 layers). A higher assemble pressure (~10bar) contributed to the acquisition of a higher rejection efficiency and lower roughness membrane. This as prepared GO membrane was applied to practical secondary effluent of a chemical synthesis pharmaceuticals wastewater. A good organic matter rejection efficiency (76%) and limited salt separation (<14%) was finally obtained. These results can promote the practical application of GO membrane and the resourcelized treatment of industrial wastewater.

Pretreatment of printing and dyeing wastewater by Fe/C micro-electrolysis combined with H2O2 process

A novel iron-carbon (Fe/C) micro-electrolysis combined with H₂O₂ (ICMH) process was proposed to pretreat the printing and dyeing wastewater (PDW), using a micro-electrolysis filling. The effects of H₂O₂ concentration, reaction time, initial pH, and Fe/C dosage on chemical oxygen demand (COD) removal rate of PDW were optimized by response surface methodology (RSM). The maximum COD removal rate was approximately 77.65% after 186 min treatment, when the concentration of H₂O₂, initial pH and the dosage of Fe/C were 8.88 g/L, 1.5 and 837 g/L, respectively. Analysis of variance (ANOVA) showed a high coefficient of determination value (R² = 0.9780). And H₂O₂ concentration and initial pH were the key factors to improve the treatment effect. UV-Vis spectra indicated that a significant blue shift at 220 nm, attributing that fused aromatic hydrocarbons were degraded effectively. 3D-EEM spectra analysis showed that the water samples of PDW mainly contained three kinds of organic matter: refractory fulvic acid, soluble microbial metabolites and aromatic proteins, and the degradation rate of these was 81.76%, 53.78% and 70.83%, respectively.

Genetic engineered color silk: fabrication of a photonics material through a bioassisted technology

Silk produced by the silkworm Bombyx mori is an attractive material because of its luster, smooth and soft texture, conspicuous mechanical strength, good biocompatibility, slow biodegradation, and carbon neutral synthesis. Silkworms have been domesticated and bred for production of better quality and quantity of silk, resulting in the development of sericulture and the textile industry. Silk is generally white, so dyeing is required to obtain colored fiber. However, the dyeing process involves harsh conditions and generates a large volume of waste water, which have environmentally and economically negative impacts. Although some strains produce cocoons that contain pigments derived from the mulberry leaves that they eat, the pigments are distributed in the sericin layer and are lost during gumming. In trials for production of colored silk by feeding silkworms on diets containing dyes, only limited species of dye molecules were incorporated into the silk threads. A method for the generation of transgenic silkworm was established in conjunction with the discovery of green fluorescent protein (GFP), and silkworms carrying the GFP gene spun silk threads that formed cocoons that glowed bright green and still retained the original properties of silk. A wide range of color variation of silk threads has been obtained by replacing the GFP gene with the genes of other fluorescent proteins chosen from the fluorescent protein palette. The genetically modified silk with photonic properties can be processed to form various products including linear threads, 2D fabrics, and 3D materials. The transgenic colored silk could be economically advantageous due to addition of a new value to silk and reduction of cost for water waste, and environmentally preferable for saving water. Here, I review the literature regarding the production methods of fluorescent silk from transgenic silkworms and present examples of genetically modified color silk.

Oxidation of azo and anthraquinonic dyes by peroxymonosulphate activated by UV light

The photochemical degradation of two azo and two anthraquinonic dyes was performed using potassium peroxymonosulphate (Oxone®) activated by UV radiation. The fast decolourization of all dyes was observed within 6 min of UV irradiation, with corresponding dye decays higher than 80%. The kinetic rate constants of the dyes' decay were determined, along with the energetic efficiency of the photochemical treatment, taking into account the influence of a few anions commonly present in real wastewaters (i.e., chloride, nitrate, carbonate/bicarbonate and phosphate ions). Chloride and carbonate/bicarbonate ions enhanced dye degradation, whereas phosphate ions exerted an inhibitory effect, and nitrates did not have a predictable influence. The dye decolourization was not associated with efficient mineralization, as suggested by the lack of a significant total organic carbon (TOC) decrease, as well as by the low concentrations of a few detected low molecular weight by-products, including nitrate ions, formaldehyde and organic acids. High molecular weight by-products were also detected by mass spectrometry analysis. The investigated process may be proposed as a convenient pre-treatment to help dye degradation in wastewater during combined treatment methods.

Low-Pressure Nanofiltration Hollow Fiber Membranes for Effective Fractionation of Dyes and Inorganic Salts in Textile Wastewater

In this work, novel loose nanofiltration (NF) hollow fiber membranes with ultrahigh water permeability and well-defined nanopore and surface charge characteristics were developed for effective fractionation of dyes and inorganic salts in textile wastewater treatment. The as-spun NF hollow fiber possesses a high pure water permeability (PWP) of 80 L·m^-2·h^-1·bar^-1 with a small pore size of 1.0 nm in diameter and a MWCO of 1000 Da. The surface modification by means of hyperbranched polyethylenimine (PEI) further lowers the pore diameter to 0.85 nm and MWCO to 680 Da. The membrane surface also becomes more hydrophilic and positively charged after the PEI modification. Because of the synergistic effects from size exclusion and charge repulsion, the newly developed NF hollow fibers show high permeation fluxes of 7.0-71.2 L·m^-2·h^-1 and great rejections of 95.5-99.9% to various dyes at a low operating pressure of 1 bar. At the same time, they have ultralow rejections of less than 10% to inorganic salts (i.e., Na₂SO₄), suggesting that more than 90% of the salts would permeate through the fibers. In addition, the two hollow fibers exhibit outstanding performance stability, low fouling tendency, and great fouling reversibility. Their fluxes can be brought back to be more than 80% of the original values by a simple physical backwash. The newly developed loose NF hollow fiber membranes may have great potential for effective fractionation and treatment of textile wastewater.

Identification and evaluation of bioremediation potential of laccase isoforms produced by Cyathus bulleri on wheat bran

Multiplicity in laccases among lignin degrading fungal species is of interest as it confers the ability to degrade several types of lignocellulosics. The combination of laccases produced on such substrates could be beneficial for treatment of complex aromatics, including dyes. In this study, we report on production of high units (679.6Ug^-1 substrate) of laccase on solid wheat bran (WB) by Cyathus bulleri. Laccase, purified from the culture filtrates of WB grown fungus, was effective for oxidation of veratryl alcohol, Reactive blue 21 and textile effluent without assistance of externally added mediators. De novo sequencing of the 'purified' laccase lead to identification of several peptides that originated from different laccase genes. Transcriptome analysis of the fungus, cultivated on WB, confirmed presence of 8 isozymes, that were re-amplified and sequenced from the cDNA prepared from WB grown fungus. The 8 isozymes were grouped into 3 classes, based on their sequence relationship with other basidiomycete laccases. The isoforms produced on WB decolorized (by ∼57%) and degraded textile effluent far more effectively, compared to laccase obtained from Basal salt cultivated fungus. The decolorization and degradation was also accompanied by more than 95% reduction in phytotoxicity.

Textile dye biodecolourization and ammonium removal over nitrite in aerobic granular sludge sequencing batch reactors

Biodecolourization of azo dye and removal of ammonium by aerobic granular sludge (AGS) was investigated under different growth conditions. AGS not previously exposed to azo dye was able to effectively decolourize azo dye under anaerobic and microaerophilic conditions. Azo dye, total organic carbon and ammoniacal nitrogen removal efficiencies of 89-100%, 79-95% and 92-100%, respectively, were achieved in the AGS reactor operated for 80days under microaerophilic conditions. Removal of carbon, nitrogen and phosphorus was not impacted by azo dye loading. Azo dye, organic carbon and ammonium were majorly removed in the anoxic period wherein bulk dissolved oxygen was ranged from 0.5 and <0.08mgL^-1. Removal of 60mgL^-1 NH₄⁺-N was associated only with smaller amounts of nitrite build-up (∼5mgL^-1 NO₂^--N) and negligible nitrate concentrations. Profiles of nitrogen compounds in individual sequencing batch reactor cycles supported the occurrence of ammonium removal over nitrite pathway. Bacterial community analysis showed enrichment of specific microorganisms capable of decolourizing azo dyes in the dye-decolourizing AGS. Dye decolourization and nutrient removal by AGS under microaerophilic conditions is a novel finding and can be further developed for treating textile wastewaters onsite or after dilution with sewage.

Saline hybrid nanoparticles with phthalocyanine and tetraphenylporphine anions showing efficient singlet-oxygen production and photocatalysis

Gd₄³⁺[AlPCS₄]₃⁴⁻ and La₄³⁺[TPPS₄]₃⁴⁻ ([AlPCS₄]⁴⁻: aluminium(iii) chlorido phthalocyanine tetrasulfonate; [TPPS₄]⁴⁻: tetraphenylporphine sulfonate) inorganic–organic hybrid nanoparticles show efficient ¹O₂ production upon daylight and red-light irradiation.