Dye Wastewater Research Articles

Stability and photocatalytic performance enhancement of sodium-doped CsPbBr3/Cs4PbBr6 nanocomposites for dye wastewater degradation

The extremely poor stability of lead halide perovskites has always been a challenge. In this paper, CsPbBr3 nanocrystals, CsPbBr3/Cs4PbBr6 nanocomposites and Na-CsPbBr3/Cs4PbBr6 nanocomposites were prepared by thermal injection and ligand-assisted reprecipitation method. The photocatalytic effect and stability of CsPbBr3 in aqueous systems were significantly improved by sodium ions doping and complexation with Cs4PbBr6. The results showed that the photocatalytic degradation rate of 5% Na-CsPbBr3 for Sudan red (III) was 57.8% within 180 min, while that of pure CsPbBr3 was only 14.47%. In the CsPbBr3/Cs4PbBr6 nanocomposites, Na-CsPbBr3/Cs4PbBr6 nanocomposites photocatalyzed nearly 94% of Sudan red (III) in 120 min, while CsPbBr3/Cs4PbBr6 photocatalyzed only 56% of organic dyes in the same time. Cs4PbBr6 can passivate CsPbBr3 in situ to enhance the stability of the perovskite material. In the four cyclic degradation experimental tests in aqueous systems, the nanocomposites maintained good stability performance. This study provides a new way to improve the catalytic performance and stability of perovskite materials.

Empowering TiO2–coated PVDF membranes stability with polyaniline and polydopamine for synergistic separation and photocatalytic enhancement in dye wastewater purification

Photocatalytic membranes are effective in removing organic dyes, but their low UV resistance poses a challenge. To address this, self-protected photocatalytic PVDF membranes were developed using polyaniline (PANI) and polydopamine (PDA), whaich are anti-oxidation polymers, as interlayers between the membrane and TiO2. PVDF membranes were first modified by a self-polymerization layer of either PANI or PDA and then coated with titanium dioxide (TiO2). The TiO2 remained firmly attached to the PANI and PDA layer, regardless of sonication and prolonged usage. The PANI and PDA layers enhanced the durability of PVDF membrane under UV/TiO2 activation. After 72 h of irradiation, PVDF–PDA–TiO2 and PVDF–PANI–TiO2 membranes exhibited no significant change. This process improved both separation and photocatalytic activity in dye wastewater treatment. The PVDF–PDA–TiO2 and PVDF–PANI–TiO2 membranes showed enhanced membrane hydrophilicity, aiding in the rejection of organic pollutants and reducing fouling. The modified membranes exhibited a significant improvement in the flux recovery rate, attributed to the synergistic effects of high hydrophilicity and photocatalytic activity. Specially, the flux recovery rate increased from 17.7% (original PVDF) to 56.3% and 37.1% for the PVDF–PDA–TiO2 membrane and PVDF–PANI–TiO2 membrane. In dye rejection tests, the PVDF‒PDA‒TiO2 membrane achieved 88% efficiency, while the PVDF‒PANI‒TiO2 reached 95.7%. Additionally, the photodegradation of Reactive Red 239 (RR239) by these membranes further improved dye removal. Despite an 11% reduction in flux, the PVDF–PDA–TiO2 membrane demonstrated greater durability and longevity. The assistance of PANI and PDA in TiO2 coating also improved COD removal (from 33 to 58–68%) and provided self-protection for photocatalytic membranes, indicating that these photocatalytic membranes can contribute to more sustainable wastewater treatment processes.

Removal of malachite green by in-situ N-doped biochar derived from wheat bran: kinetics, isotherms, and adsorption mechanism study

The biomass-based adsorbents offer a promising solution for wastewater decolorization owing to their superior specific surface area, low-budget, high adsorption capacities, and environmental sustainability. In this work, wheat bran (WB) was used as raw material for the production of in situ N-doped biochar through a molten salt template method, and the adsorption characteristics of Malachite Green (MG) onto biochars prepared from WB by immersing and non-immersing (BC–NaK and BC–NaK-n) in the mixed salt solution (NaCl and KCl) were investigated. The experimental results indicated that the adsorption capacity of MG onto the BC–NaK was significantly better than BC–NaK-n, which was attributed to the rich functional groups and well-developed pore structure of BC–NaK. The adsorption equilibrium data of MG onto the BC–NaK was fitted well to Sips and Koble-Corrigan isotherm models and adsorption process of MG was spontaneous and endothermic. Meanwhile, the pseudo-second-order model was successfully applied to depict the adsorption process of MG. Furthermore, the adsorption of MG onto BC–NaK was primarily regulated by H-bonding, π–π interaction, hydrophobic interaction, electrostatic interaction. The maximum saturated adsorption capacity of the BC–NaK was 880.14 ± 9.35 mg g−1 at 298 K, further demonstrating that biochar prepared from wheat bran provided a long-term development strategy for dye wastewater treatment.

A Piezoelectric Electrospun Nanofiber mat (Kaolin/PVDF) for the Degradation of Methylene Blue in Water

Organic compounds of various classes have been identified as major pollutants commonly detected in several environmental freshwaters. As a potential solution, electrospun mat-like nanofibers comprising polyvinylidene fluoride (PVDF) nanofibers and kaolin clay composite were synthesized for the degradation of methylene blue dye in wastewater using piezocatalytic technique. The kaolin/PVDF composites were characterized with SEM, XRD, FTIR, Chronoamperometry and electrochemical impedance spectroscopy. The poling of the piezoelectric charges of the electrospun mat-like nanofibers, enhanced by the presence of the crystalline nature of the kaolin clay occasioned the generation of reactive species upon exposure to ultrasonic vibration. Moreover, ultrasound waves in the system prevented passivation of the mat’s active surface during piezocatalysis through continuous cleaning action. A degradation efficiency of 100% was obtained from the degradation of methylene blue dye using the synthesized kaolin/PVDF composites during piezocatalysis. This result positions the nanofiber as an effective catalyst in wastewater treatment applications.Graphical

Enhanced photodegradation of textile dye wastewater using silane/polymer doped ZnO nanocomposites and antibacterial activity

Accumulation of textile dye wastewater is major global issue that causes negative impact to the ecosystem. This study focuses on industrial textile dye effluent treatment by photodegradation, and degradation of Malachite green dye under sunlight, visible and UV light. ZnO demonstrated hexagonal wurtzite structure with average crystallite size 38 nm for ZnO/PEG, 21 nm for ZnO/PEG/VTES and 17 nm for ZnO/PEG/VTMS. Field Emission Scanning Electron Microscopy and Energy Dispersive Spectroscopy revealed nanometer sized particles and purity. Bandgap energy and particle size of ZnO/PEG/VTMS is 102 nm and 3.134 eV is lesser than ZnO/PEG (147 nm, 3.181 eV) and ZnO/PEG/VTES (109 nm, 3.151 eV). Photoluminescence analysis revealed reduced recombination rate of ZnO/PEG/VTMS. Antibacterial efficacy of ZnO/PEG/VTMS was tested against Staphylococcus aureus (35 mm) and Escherichia coli (29 mm). Photodegradation of textile dye wastewater by ZnO/PEG/VTMS under visible and UV light exposure revealed an effective way for textile dye effluent treatment, which maintained its efficiency even after five photodegradation cycles.

Synthesis of bare and modified zerovalent iron nanoparticles and their use in porous polylactic acid composites for methyl orange removal

The main objective of this study was to assess the efficacy of two types of immobilised zerovalent iron nanoparticles (nZVI) incorporated into a porous biopolymer matrix of polylactic acid (PLA) as a novel multifunctional composite system for potential use in dye wastewater treatment. The study involved the preparation of unmodified and 2,6-pyridinedicarboxylic acid (PDCA) modified nZVI material using liquid phase reduction method. Zeta potential measurement and UV-Vis spectrophotometry revealed that the ligand-modified nZVI particles exhibited better dispersion stability in aqueous media than bare particles. SEM-EDS analysis showed a higher oxidation state of the ligand-modified nZVI particles and good dispersion and adhesion of nZVI particles in the mesoporous structure of PLA matrix. The removal efficiency of methyl orange was determined spectrophotometrically where a high efficiency (above 90 %) for high concentration of bare nZVI was detected. Its composites also showed an efficiency of 75 – 100 %. However, modified nZVI showed much lower efficiency, especially after embedding in the PLA matrix.

A Zn-Ca-Based Metallic Glass Composite Material for Rapid Degradation of Azo Dyes.

The catalytic capabilities of metals in degrading azo dyes have garnered extensive interest; however, selecting highly efficient metals remains a significant challenge. We have developed a Zn-Ca-based metallic glass composite which shows outstanding degradation efficiency for Direct Blue 6. This alloy comprises a Zn2Ca crystalline phase and an amorphous matrix, allowing for the degradation of azo dyes within minutes in a wide temperature range of 0-60 °C. Kinetic calculations reveal an exceptionally low activation energy of 8.99 kJ/mol. The rapid degradation is attributed to the active element Ca and the unique amorphous structure of the matrix, which not only facilitates abundant redox conditions but also minimizes the hydrolysis of the active element. The newly developed metallic glass composite exhibits a notably higher azo dye degradation rate compared to those of general metallic glasses, offering a new avenue for the rapid degradation of azo dyes. This paper holds significant importance for the development of novel azo dye wastewater treatment agents.

Defects-rich MgFe LDH: A high-capacity adsorbent for methyl orange wastewater

Dye pollution is a common pollutant in wastewater that poses a serious threat to human health. Layered double hydroxide (LDH) is a commonly used adsorbent for dye removal. However, its adsorption efficiency is significantly limited by the limited adsorption active sites of the adsorbent. In this paper, a defects-rich MgFe LDH adsorbent for anionic dye wastewater was synthesized by a simple hydrothermal method and alkaline etching. Different analytical techniques, such as XRD, FT-IR, SEM, TEM, XPS, and N2 adsorption-desorption isotherm, were used to verify the chemical composition and surface characteristics of the materials, and the effects of pH, temperature, and contact time on the adsorption effect of methyl orange and the adsorption mechanism were analyzed. Alkaline etching of Al and Zn in the laminate generated defects that expose unsaturated coordination centers and create abundant adsorption sites, which can electrostatically attract and coordinate with dye ions. At 25°C, the adsorption capacity of MgFe LDH with Al etched and MgFe LDH with Zn etched for methyl orange dye reached 1722 mg/g and 1685 mg/g, respectively, much higher than that of MgFe LDH (544 mg/g). This work provides a promising method for the removal of dye wastewater by adsorption and a new idea for the design and development of high-performance dye wastewater adsorbents.

Heterogeneous Fenton catalytic degradation of organic dyes and the optimization using the central composite design − Response surface methodology

Heterogeneous Fenton catalysts are extremely important in the degradation of organic dyes in wastewater. In this study, a novel heterogeneous Fenton catalyst with sand grains as the carrier was investigated its performance in degrading organic dyes. The catalyst endows with excellent dye degradation efficiency in H2O2 solution, and the degradation rate of Methylene blue (MB), Crystal Violet (CV), and Congo Red (CR) is 84.0 %, 87.2 %, and 76.0 % within 80 min at the catalyst concentration of 0.1 g/L, respectively. The influences of degradation conditions on the degradation rate of MB wastewater were studied. The results shows that dye concentration, pH value, degradation temperature, H2O2 concentration, and catalyst concentration all affect the degradation rate. The dye degradation model was built based on the central composite design (CCD) − response surface method (RSM). It shows that pH value, degradation temperature, H2O2 concentration, and catalyst concentration are significant influencing factors of degradation rate; the order of importance for these factors is: catalyst concentration > H2O2 concentration > pH value > degradation temperature; the optimal degradation conditions are the pH value of 4.00, the degradation temperature of 36 °C, the H2O2 concentration of 0.96 mol/L, the catalyst concentration of 0.21 g/L, and the degradation rate of MB reaches 96.27 %, which is much higher than the optimal value of 92.50 % obtained by single factor method at the same dye concentration.

Effect of spunbond nonwoven microplastics on dye wastewater treatment via hydrogen peroxide–based catalyst–assisted advanced oxidation processes

The increasing prevalence of microplastics (MPs) in textile wastewater poses significant challenges for treatment processes. This study evaluates the impact of MPs on the decolorization of Reactive Red 239 (RR239) dye using hydrogen peroxide–based advanced oxidation processes, specifically UV/H2O2, H2O2/Fe2+ (Fenton) and H2O2/Fe2+/UV (photo–Fenton). UV/H2O2 oxidation exhibited superior decolorization efficiency compared to both Fenton and photo–Fenton processes. The optimal decolorization efficiency for RR239 was achieved at 94.1% at pH 3 in the Fenton process with H2O2 and Fe2+ concentrations of 2.5 mg/L and 12.5 mg/L, respectively. For UV/H2O2 oxidation, complete decolorization was achieved in 60 min at an optimal UV light intensity of 11 W and H2O2 of 75 mg/L at neutral pH. The presence of spunbond nonwoven MPs in RR239 wastewater significantly inhibited decolorization efficiency and kinetic rate constants. The pseudo–second–order rate constant (Kapp) for the Fenton process without MPs was 0.0101 M–1 min–1, whereas the presence of MPs reduced the Kapp to a range of 0.0026 to 0.0034 M–1 min–1. The UV/H2O2 process maintained a Kapp of 0.1301 min–1 as pseudo–first–order regardless of MP content but was affected by MP size. MPs in the size range of 200–500 µm improved decolorization efficiency, while larger MPs (500–1000 µm) reduced it. The results highlight the necessity of separating MPs to maintain high decolorization efficiency in dye wastewater treatment processes. The findings suggest that optimizing these parameters can enhance the efficacy of advanced oxidation processes in treating dye wastewater containing MPs.

One-Pot Preparation of Layered Double Hydroxide-Engineered Boric Acid Root and Application in Wastewater.

Heavy metals and organic pollutants are prevalent in water bodies, causing great damage to the environment and human beings. Hence, it is urgent to develop a kind of adsorbent with good performance. Anion interlacing layered double hydroxides (LDHs) are a promising adsorbent for the sustainable removal of heavy metal ions and dyes from wastewater. Using aluminum chloride, zinc chloride and ammonium pentaborate tetrahydrate (NH4B5O8 · 4H2O, BA) as raw materials, the LDHs complex (BA-LDHs) of B5O8- intercalation was prepared by one-step hydrothermal method. The BA-LDHs samples were characterized by a X-ray powder diffractometer (XRD), scanning electron microscope (SEM), Fourier transform infrared spectrometer (FT-IR) and the Brunauer-Emmett-Teller (BET) method. The results showed that B5O8- was successfully intercalated. Adsorption experimental results suggested that BA-LDHs possess a maximum adsorption capacity of 18.7, 57.5, 70.2, and 3.12 mg·g-1 for Cd(II), Cu(II), Cr(VI) and Methylene blue (MB) at Cs = 2 g·L-1, respectively. The adsorption experiment conforms to the Langmuir and Freundlich adsorption models, and the kinetic adsorption data are well fitted by the pseudo-second-order adsorption kinetic equation. The as-prepared BA-LDHs have potential application prospects in the removal of heavy metals and dyes in wastewater. More importantly, they also provide a strategy for preparing selective adsorbents.

Economic and environmentally friendly anionic flocculant synthesized by starch-acrylic acid-itaconic acid grafting and efficient treatment of cationic dye wastewater

Starch-based flocculants are environmentally friendly and high-performance products, potentially applied in wastewater treatment with low operation cost and ecological risk. In this study, we successfully synthesized a ternary anionic copolymer of starch-acrylic acid-itaconic acid (SAI) through graft copolymerization. The synthesis conditions were optimized based on flocculation efficiency against cationic crystal violet (CV), and subsequent applicability was conducted under various environmental conditions. The results indicate that SAI exhibited outstanding decolorization efficiency under wide scopes of pH, temperature, and ionic strength. Most importantly, SAI achieved a remarkable decolorization rate of 91.2 % for 100 mg/L CV dye at a low concentration of 25 mg/L, accounting for one-fourth of the cost operated with commercial polyacrylamide. Compared to binary flocculants, SAI demonstrates superior flocculation performance too. The flocculation mechanism is primarily attributed to the combined effects of charge neutralization, bridging, and sweeping. SAI flocculants possess characteristics of high efficiency, environmental friendliness, and cost-effectiveness, thus presenting broad prospects for the treatment of dye wastewater.

Electrocatalytic hydrogen evolution coupled with dye hydrogenation reactions for sustainable wastewater treatment using transition-metal (Fe, Co, Ni, Cu) nanoparticles with ZnO nanowire supports

A water electrolysis coupled with chemical reduction strategy is proposed to realize sustainable wastewater treatment. Correspondingly, a series of transition-metal (e.g., iron, cobalt, nickel and copper) nanoparticles anchored on zinc oxide nanowire array (ZnO NA) with bifunctional catalytic activity for hydrogen evolution reaction together with dye hydrogenation reaction (HER/DHR) are developed, while their catalytic activity are comparatively investigated at the same time. This renewable strategy with environmental and economic benefits exhibits high-efficiency treatment capability towards various dye wastewaters. For example, a typical system based on nickel nanoparticles with ZnO NA supports, which exhibits higher catalytic activity towards the HER/DHR than those of other three counterparts under the same conditions, can transform waste 4-nitrophenol into valuable 4-aminophenol with an apparent rate constant of 36.95 × 10-3 min−1 and a conversion rate of 98.32 %, thereby achieving dye decolorization and resource regeneration simultaneously. Its efficiency is significantly superior to that of chemical method dependent on traditional reducing agents and commercial nickel materials, demonstrating its stronger competitiveness. It is mainly benefited from the interface synergistic effect of nickel nanoparticles and zinc oxide nanowires. This novel system is expected to replace conventional sewage remediation technologies for efficient, inexpensive, and eco-friendly dye degradation, and thus is very important for energy and environmental sustainability.

Waste-Derived Carbon Nano-Onions for the Removal of Organic Dye from Wastewater and Phytotoxicity Studies.

Dyes are extensively employed in industries, namely, textiles, cosmetics, paper, pharmaceuticals, tanning, etc. The effluent released from these industries contains various kinds of harmful dyes that adversely impact living beings and the environment due to their recalcitrant and toxic nature. In this study, an effort has been made to eliminate the methylene blue (MB) from wastewater using carbon nano-onions (CNOs) produced from waste frying oil (WFO) using an economical and eco-friendly wick pyrolysis method. The impact of process variables, namely, pH, temperature, process time, MB dye concentration, and adsorbent, was examined for optimum dye removal. The dye removal efficiency (RE) of 99.78% was obtained in 20 min under optimum conditions. The pseudo-second-order model demonstrated a better kinetic fitting with the experimental data. The Langmuir model represented the maximum adsorption capacity (q max) of 43.11 ± 2.56 mg g-1. The regeneration studies demonstrated that the CNOs achieved ∼99.6% MB dye removal over three cycles. Brassica nigra seeds irrigated in treated wastewater showed better growth (3.29 cm) than untreated dye wastewater, which confirms the environmental sustainability of the overall process.

Computational intelligence modelling of methylene blue adsorption by metal-organic frameworks

ABSTRACT Computational intelligence models for wastewater treatment utilise mathematical algorithms to simulate and optimise the processes involved in the removal of pollutants from wastewater, aiding in the design and operation of the wastewater treatment plant. The aim of this work was to compare the efficiency of computational models in modelling the dynamic adsorption of dyes. Metal-organic frameworks (MOFs) are considered as adsorbents because of their excellent properties. Further, the dataset used for this study was sourced from literature pertaining to the adsorption of methylene blue (MB), which is one of the commonly found dyes in wastewater. Adsorption parameters considered for the study are initial concentration, bed height, flow rate, pH and time, for the continuous adsorption process. The efficacy of the selected computational models was compared by employing various statistical metrics. Moreover, the results show the efficiency of artificial neural network and radial basis function neural network models is superior to other models based on R2 and mean square error, which were in the range of 0.95–0.999 and 10–3–10–5, respectively. In summary, the computational intelligence models serve as the best tools for the prediction of the adsorption performance of MOFs for MB.

Preparation and performance of quaternary ammonium salt‐containing methacrylate copolymer‐based ultrafiltration membranes

AbstractUltrafiltration (UF) membranes with excellent dye removal and antibacterial activity are highly desired in dye wastewater treatment, and more importantly environmental protection puts high demands on polymeric membrane materials. In this work, three methacrylate copolymers containing quaternary ammonium salt were synthesized to cast UF membranes. The physicochemical property, structural evolution, dye separation, and antibacterial activity of as‐prepared membranes were systematically investigated. With increased content of the hydrophilic monomer allyl polypropylene glycol (APPG) in the feed, the wettability and positive charge of the resultant membranes were enhanced. Remarkably, the supporting layer of membranes changed from finger‐like pore structure to sponge‐like pore structure by increasing APPG content, and the sponge‐like membranes showed higher retention rates for dyes (99.78% for victoria blue B, 90.49% for methylene blue, and 97.43% for methyl blue) compared with the finger‐like membranes. Besides, the sponge‐like membranes exhibited high rejection for vctoria blue B (>99%) in dye/salt mixture and simultaneously low rejection for salts (<10%), indicating effective selective separation to dye/salt mixture, and also achieved easy regeneration. It was also found that increased hydrophilicity and positive charge endowed membranes with better antibacterial activity. This work will provide an alternative for dye/salt selective separation in dye effluent treatment.

Enhanced filtration membranes with graphene oxide and tannic acid for textile industry wastewater dye removal

ABSTRACT A novel modification technique employing a layer-by-layer (LbL) self-assembly method, integrated with a pressure-assisted filtration system, was developed for enhancing a commercial polyethersulfone (PES) microfiltration (MF) membrane. This modification involved the incorporation of tannic acid (TA) in conjunction with graphene oxide (GO) nanosheets. The effectiveness of the LbL method was confirmed through comprehensive characterization analyses, including ATR-FTIR, SEM, water contact angle (WCA), and mean pore size measurements, comparing the modified membrane with the original commercial one. Sixteen variations of PES MF membranes were superficially modified using a three-factorial design, with the deposited amount of TA and GO as key factors. The influence of these factors on the morphology and performance of the membranes was systematically investigated, focusing on parameters such as pure water permeability (PWP), blue corazol (BC) dye removal efficiency, and flux recovery rate (FRR). The membranes produced with the maximum amount of GO (0.1 mg, 0.55 wt%) and TA as the inner and outer layers demonstrated remarkable FRR and significant BC removal, exceeding 80%. Notably, there was no significant difference observed when using either 0.2 (1.11 wt%) or 0.4 mg (2.22 wt%) in the first layer, as indicated by the Tukey mean test. Furthermore, the modified membrane designated as MF/TA0.4GO0.1TA0.4 was evaluated in the filtration of a simulated dye bath wastewater, exhibiting a BC removal efficiency of 49.20% and a salt removal efficiency of 27.74%. In conclusion, the novel PES MF membrane modification proposed in this study effectively enhances the key properties of pressure-driven separation processes.

Facile single-step synthesis of ZnFe2O4@biochar for synergistic adsorption and photo-Fenton degradation of RB and RBR binary dyes

BackgroundBiochar ferrite composites have attracted widespread interest in adsorption and photocatalysis. MethodsZnFe2O4@biochar (ZnFe2O4@C) photo-Fenton catalyst was synthesized by single-step pyrolysis strategy and characterized by SEM-EDS, FT-IR, XRD, BET, XPS, VSM, UV–vis DRS. The activity of ZnFe2O4@C was investigated via rhodamine B (RB) and reactive brilliant red X-3B (RBR) binary dyes photo-Fenton degradation. Significant FindingsZnFe2O4 was uniformly anchored on biochar and formed magnet-separable ZnFe2O4@C. ZnFe2O4@C exhibited synergistic adsorption and photo-Fenton activity. Combination ZnFe2O4 with biochar reduced the recombination rate of photo-generated carriers, and effectively accelerated the degradation of RB and RBR binary dyes. Under the optimal conditions, the removal efficiency of RB and RBR were both more than 99.00%, and the reaction rate constants were 0.1276 min–1 and 0.0928 min–1, respectively. The photo-generated holes and •OH were the main active species. The possible degradation pathways were involved in cleavage of C–N, N-de-ethylation, chromophore cleavage and benzene ring opening for RB, and deionization, cleavage of N = N and C–N, oxidization and benzene ring opening for RBR. This work provided a facile single-step synthesis strategy for ZnFe2O4@biochar photo-Fenton catalyst, which was magnet-separable, environment-friendly, pH adaptability-widely, and there was the potentiality for organic dyes wastewater treatment.

Assessment of Natural Bentonite Efficacy for Dye Removal in Textile Wastewater Treatment : Implication for Mitigating River Citarum Pollution

Textile industries contribute significantly to the economy but release harmful pollutants into the environment, especially rivers. The effluent from the textile industry contained toxic dyes that can harm the river ecosystem. Several studies have been conducted to reduce toxic dyes in a river system using bentonite as an adsorbent to reduce river pollution effectively. However, the effectiveness of bentonite still needs to be tested again using textile liquid waste that has not gone through any waste processing at all. Citarum is one of the main rivers on Java Island, which suffers from textile effluent, especially azo dyes which are toxic, mutagenic and carcinogenic which can harm the aquatic ecosystem. Therefore, this study aims to implement natural bentonite as an adsorbent to remove dyes from textile wastewater. We performed a laboratory test to adsorption on bentonite and textile wastewater considering the variation of adsorbent weight of 10 g and 20 g in 100 mL of textile wastewater stirred in an Erlenmeyer flask at room temperature for 0-300 minutes. The initial concentration of textile wastewater used was 10%, 30%, and 50%. We found that the maximum dye removal efficiency was 91.25% with 10% initial concentration treatment, 20 g adsorbent weight, and 60 minutes contact time. Longer contact time will increase the removal efficiency and adsorption capacity, while higher adsorbent dosage will decrease the concentration of dyes in wastewater. Efficient textile wastewater treatment has improved water quality, effectively meeting river water quality standards and environmental regulations.

Bi-doped g-C3N4/Bi2WO6 ternary composites for superior photocatalytic degradation of reactive orange 16 under visible light irradiation

Because of unrestricted disposal, the concentration of reactive dyes in wastewater is gradually increasing. Owing to their eco-toxicity their removal becomes so crucial. In this regard, Bi(0)-doped g-C3N4/Bi2WO6 (g-C3N4/Bi@Bi2WO6) nanocomposites were prepared by wet impregnation followed by calcination. Remarkably, the Bi(0) doping occurs concertedly during the preparation of Bi2WO6 without the addition of any extra reducing agent. The efficacy of the photocatalyst for eliminating reactive orange 16 was evaluated under visible light irradiation. XRD, FESEM, HRTEM, DRS, XPS, BET, etc., were employed to characterize these hybrids. The presence of Bi(0) was confirmed by HRTEM and XPS. Increasing the g-C3N4 content enhances the specific surface and reduces the charge transfer resistance. Among the various photocatalysts, the 20 wt% g-C3N4/Bi@Bi2WO6 hybrid owned the highest degradation efficiency of 89 % after 300 min of reaction time. The controlled experiments confirm the participation of holes and superoxide anions during the reactions. The various reaction intermediates were detected by HRMS providing the necessary evidence about the mechanism. The heterostructure possesses excellent reusability and stability. Due to enhanced catalytic activity, high stability, and ease of synthesis, the reported composite can be considered as a promising catalyst for the degradation of pollutants.