Industrial Dye Wastewater Research Articles

A loose polyethersulfone hybrid nanofiltration membrane incorporated with polyethyleneimine-decorated silica nanoparticles for highly-efficient dye/salt separation

Loose nanofiltration (LNF) is a newly-developing technology for desalting dye-containing saline effluents, but suffers from membrane materials with low permeance and poor dye/salt separation selectivity. Herein, a hybrid polyethersulfone (PES) LNF membrane for dye/salt separation was prepared via a nonsolvent-induced phase inversion method, which was carried out using polyethyleneimine (PEI)-modified silica nanoparticles as a dopant. This design not only featured a hybrid PES LNF membrane with high porosity and small mean pore size, but also partially neutralized its charge and enhanced its hydrophilicity. Hybrid PES LNF membrane from a 21-wt% PES solution with 3-wt% PEI-decorated silica nanoparticles addition was demonstrated to achieve high water permeance (92.0 L m−2 h−1 bar−1) and dyes retention ratio (98.4 % for Congo Red, 98.8 % for Nile Blue A, and 95.1 % for Methyl Blue) accompanied with fully-pass for various salts (Na2SO4, NaCl, MgCl2 and CaCl2). In addition, the hybrid membrane exerted excellent resistances to strong acidic, oxidative and hot water (90 °C) environments and exhibited a pH-sensitive permeability. Multicycle test revealed that the hybrid membrane had high permeance recovery ratio (>92.8 %) and maintained its high dye retention and complete salt permeation even after 10 cycles, manifesting its outstanding fouling resistance and recyclability. Besides, the hybrid membrane repelled 92.6 % of dyes from a simulated wastewater consisting of multiple industry-applied direct dyes and salts after 12 h consecutive test, but allow 100 % of mixed salts passing through the membrane, proving its practical applicability to industrial dyeing wastewater. This study provided a simple and economically feasible route to high-performance LNF membrane production for dye/salt separation, thus popularizing LNF process in dyeing wastewater treatment, organic products purification, and resource recovery.

Distinguishable photorecycling of PVDF nanocomposites membrane for reactive yellow 145 dye and real industrial wastewater treatment by different photocatalytic processes

This paper investigates the photocatalytic performance and recyclability of PVDF-MWCNTs-TiO2 nanocomposite membranes for the treatment of textile wastewater under sunlight irradiation. The nanocomposites were fabricated by incorporating varying weight ratios of MWCNTs-TiO2 (1 %, 3 %, 6 %, and 9 %) into PVDF matrices using a solvent casting method. Optimal loading of MWCNTs-TiO2 at 9 wt% resulted in nanocomposites with enhanced surface area (94.15 m2/g), reduced band gap (2.38 eV), uniform dispersion of nanoparticles, and abundant surface hydroxyl groups. Under Xenon lamp irradiation, the optimized PVDF-9 %(MWCNTs-9 %TiO2) nanocomposite achieved a high apparent reaction rate constant (kapp) of 9.92 × 10−3 s−1 for photocatalytic degradation of the model dye Reactive Yellow 145. Significantly, when tested on-site at a Saudi Arabian textile facility over 6 months, this nanocomposite effectively reduced the chemical oxygen demand (COD) of real wastewater samples to regulatory limits of 1000 ppm under natural sunlight irradiation. The COD values were lowered from an initial 5050–6200 ppm to a final range of 785–945 ppm using the PVDF-9 %(MWCNTs-9 %TiO2) membrane. Furthermore, the optimized nanocomposite exhibited good recyclability, retaining around 87 % of its initial activity after 8 reuse cycles for industrial wastewater treatment. The excellent photocatalytic efficiency and reusability of the MWCNTs-TiO2 modified PVDF nanocomposite under solar irradiation highlight its promise as a sustainable membrane technology for environmental remediation.

Multivariate optimization of organic matter and color removal from textile dyeing industry wastewater by ultraviolet-activated oxidants

This study investigated the efficiency of ultraviolet (UV) activation of the oxidants that are used in advanced oxidation processes in textile dyeing industry wastewater treatment with high concentrations of refractory organic matter and strong color. The effect of peroxymonosulfate (PMS), peroxydisulfate (PS), hydrogen peroxide (HP), percarbonate (PC), and chlorine as oxidants in UV-based processes was first evaluated. The two processes with the greatest removal efficiency were determined as UV/PS and UV/PMS. Then the operating parameters for UV/PS and UV/PMS were optimized by the Box-Behnken Design (BBD). Process parameters for both processes were oxidant dosage, initial pH, and reaction time whereas system responses were chemical oxygen demand (COD), UV254, and color removal efficiency. Under optimum conditions in the UV/PS process (pH 5.54, PS dosage 24.4 mM, and reaction time 117 min), COD, UV254, and color removal efficiency were 83.21 %, 92.14 %, and 93.87 %, respectively. Under optimum conditions in the UV/PMS process (pH 5.83, PMS dosage 23.1 mM, and reaction time 120 min), COD, UV254, and color removal efficiency were 66.89 %, 78.45 %, and 96.89 %, respectively. The R2 of all the models that applied for the system responses of both processes was nearly one and the adj R2 values were very near to the R2 values. These findings showed that the BBD is efficient, suitable, and significant in modeling the removal of pollutants in textile dyeing industry wastewater by UV/PS and UV/PMS processes. Electrical Energy per Order (EE/O) calculations for UV/PS and UV/PMS processes were 101 and 167 kWh/m3 for optimum conditions, respectively. The results showed that both UV/PS and UV/PMS processes are effective; however, the UV/PS process is more economical and effective concerning pollutant removal efficiency and EE/O calculations.

Biocatalytic enhancement of laccase immobilized on ZnFe2O4 nanoparticles and its application for degradation of textile dyes

Efficient and convenient treatment of industrial dyeing wastewater is of a great significance to guarantee human and animal health. This work presented the enhanced catalytic activity at pH 3.0 of laccase immobilized on amino-functionalized ZnFe2O4 nanoparticles (ZnFe2O4-laccase) and its application for degradation of textile dyes. Due to the existence of a large number of oxygen vacancies on the surface of the ZnFe2O4 nanoparticles, negative ions accumulated on the magnetic carriers, which resulted in a harsh optimal pH value of the ZnFe2O4-laccase. Laccase activity assays revealed that the ZnFe2O4-laccase possessed superior pH and thermal stabilities, excellent reusability, and noticeable organic solvent tolerance. Meanwhile, the ZnFe2O4-laccase presented efficient and sustainable degradation of high concentrations of textile dyes. The initial decoloration efficiencies of malachite green (MG), brilliant green (BG), azophloxine, crystal violet (CV), reactive blue 19 (RB19) and procion red MX-5B were approximately 99.1%, 95.0%, 93.3%, 87.4%, 86.1% and 85.3%, respectively. After 10 consecutive reuses, the degradation rates of the textile dyes still maintained about 98.2%, 92.5%, 83.2%, 81.5%, 79.8% and 65.9%, respectively. The excellent dye degradation properties indicate that the ZnFe2O4-laccase has a technical application in high concentrations of dyestuffs treatment.

High removal performance of reactive blue 5G dye from industrial dyeing wastewater using biochar in a fixed-bed adsorption system: Approaches and insights based on modeling, isotherms, and thermodynamics study

In an eco-friendly context, an adsorption study was performed in a fixed-bed column system to remove organic pollutants from dyeing wastewater, testing preliminary theoretical models and reactive blue 5G (RB5G) dye as a reference pollutant and tilapia bone-based biochar as an alternative adsorbent. Adsorption approaches in removing RB5G dye molecules from synthetic solutions were performed to understand better based on a reliable mathematical representation and provide insights and strategies into treating dyeing wastewater. Initial dye concentration, pH, temperature, and stirring velocity were used as process variables to search for maximal capacity in batch mode. Thermodynamic analysis and a series of phenomenological kinetic models were applied to understand and interpret the mechanisms and develop a predictive model for a fixed-bed column adsorption system, trying to minimize the total organic carbon (TOC) in dyeing wastewater. An intraparticle mass transfer resistance model and the Langmuir-BET isotherm better represented kinetic and equilibrium data, respectively. In the Langmuir-BET model context, the first monolayer has systematically changed its predicted Langmuir adsorption capacity from 18 mg g−1 to 31 mg g−1 being favored by the increase in temperature of 30 to 60 °C, respectively, with the lowest Gibbs free energies for the multilayer formation ruled by weak physical interaction. Theoretical values of the breakpoint, full saturation time, and useful column height were well predicted related to their experimental ones, including the better fitting of all adsorption curve patterns in a fixed-bed adsorption column system with an adsorption capacity of 30.4 mg g−1 (at 50 °C) for an inlet of 200 mg L−1 RB5G solution resembling almost the same value found in batch mode (30.9 mg g−1). After treating the dyeing wastewater characterized by 75 mg L−1 RB5G dye, the adsorption capacity of 23.3 mg g−1 was attained with a 12% loss in comparison with the expected one for a synthetic RB5G solution due to adsorptive competition with other organic pollutants. Finally, a final TOC value near 5.0 mg L−1, the maximum allowed for the Brazilian environmental council, was attained with an almost zero RB5G concentration after a 5-h breakpoint.

Evaluation of biosynthesized GO@CeO2 nanocomposites as a catalyst for UV-assisted degradation of organic dyes and phytotoxicity studies

The availability of clean water for human use is one of the world's most pressing problems, and scientists are working hard to find a solution. Water that has been treated using nanotechnology is free of harmful microbes and organic dyes, making it superior to older treatment techniques. This research investigated the effects of light on graphene oxide nanocomposites infused with biosynthesized CeO2 nanoparticles. Numerous techniques were applied to characterize the as-prepared nanocomposites, including HRTEM, FTIR, XRD, XPS, UV-Vis, and Raman spectroscopy. Adsorbing and photodegrading CV, MB, and AO from an aqueous solution was accomplished with the help of a GO@CeO2 nanocomposite. Adsorption and photodegradation of the GO@CeO2 nanocomposite occur significantly more rapidly and efficiently in the presence of visible light than in the absence of light. The GO@CeO2 compound was able to eliminate 85 % of CV, 91.81 % of MB, and 87 % of AO in under 90 min. Adsorption alone is ineffective against CV, MB, and AO, but photodegradation in visible light is superior. According to the results of a research study with fenugreek plants, the treated effluents do not have any phytotoxic effects. Degradation of organic dyes in industrial wastewater using the GO@CeO2 catalyst was proven to be an efficient and inexpensive method.

Fabrication of activated carbon from Acacia Crassicarpa bark by carbothermal functionalization for adsorptive removal the dyes in aqueous solution

Activated carbon adsorbent prepared from Acacia Crassicarpa bark has been successfully synthesized via carbonization and chemical activation processes to investigate the elimination of hazardous dyes in industrial wastewater, specifically the anionic dye methyl orange (MO) and the cationic dye methylene blue (MB) in this study. The Acacia Crassicarpa bark was washed with distilled water and dried it in an electric oven at 100 °C. The carbonization process was carried out at a temperature of 1050 °C in the Argon atmosphere and thoroughly was activated by NaOH. The results showed that a high BET surface area of 711.05 m2/g was obtained. XRD pattern presented that the high content of crystalline carbon was formed and carbon content was achieved approximately 83%. Also, SEM images illustrated the average size of carbon is 2.58 μm and surface structure of activated carbon appeared the pores inside the particle. The Langmuir was observed to fit the adsorption data well. The maximum equilibrium adsorption capacities predicted by the Langmuir isotherm were found to be 156.25 mg/g and 144.09 mg/g for MO and MB, respectively. All of those results confirm that the activated carbon originated from Acacia Crassicarpa bark can potentially be applied for water purification treatment. In comparison to traditional charcoal, this activated carbon presents numerous advantages. Notably, it can integrate into the biomass energy cycle, improve filtration capabilities, and result in cost savings.

Evaluation of Adsorbent Biomaterials Based on Coconut Mesocarp for Treatment of Wastewater Contaminated with Tartrazine Dye

The presence of synthetic dyes in industrial wastewater poses significant environmental and health concerns due to their persistent nature and potential toxicity. Tartrazine is a synthetic yellow dye known for its stability and resistance to conventional treatment methods. As a result, its discharge into natural water bodies can lead to adverse ecological impacts and can jeopardize public health. The objective of this work was to functionalize coconut shells (CSs), coconut cellulose (CC), and modified coconut cellulose (MCC) bioadsorbents with cetyl trimethyl ammonium chloride (CTAC) for their use in the elimination by adsorption of the dye tartrazine in aqueous solutions. CC was synthesized through a double extraction with sodium hydroxide, and a chemical treatment was performed with CTAC at 100 mmol L−1. The final dye concentration was determined through UV-Vis at 500 nm. An FTIR analysis showed multiple active sites, represented in groups such as hydroxyl, COO-, NHx-, and hydrocarbon compounds. Increasing the initial concentration had a positive effect on the efficiency of the process, reaching 99% removal with an adsorption capacity of 11.89 mg/g at equilibrium using MCC. The test showed that equilibrium was reached after 30 min. Initially, the removal of the dyes was rapid, about 97% of the contaminant being removed in the first 5 min. The Langmuir and Freundlich models were satisfactorily fitted to the adsorption isotherm, showing physical and chemical adsorption. It can be concluded that MCC is a promising bioadsorbent for the removal of tartrazine dye in aqueous solutions.

Performance evaluation of direct Z-scheme based modified titania composite for photocatalytic degradation of organic pollutants

Ceramic materials are widely used as a photocatalyst due to their low cost synthesis, photostability, suitable bandgap and excellent photodegradation properties. One such material is TiO2 however, it shows very low efficiency because it is only active in UV region (4 % of solar spectrum), have high holes-electrons recombination and low adsorption capacity. To address these limitations, highly active modified TiO2 based ceramic materials like Er2O3/TiO2, Molybdenum loaded TiO2 and TiO2/Er2O3 photocatalysts were synthesized by Sol-gel method. These synthesized photocatalysts were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL) emission spectroscopy, UV–vis spectra, and Brunauer–Emmett–Teller (BET). The incorporation of Er2O3 into TiO2 and metal loading of molybdenum reduced the bandgap of TiO2 from 3.3 eV to 3.25 eV, 3.1 eV, and 3.09 eV for TiO2–Er2O3, Mo loaded TiO2 and Mo loaded TiO2–Er2O3, respectively. BET analysis revealed the enhancement of surface area by adding Er2O3 and Mo (from SBET = 39.9 m2/g to SBET = 67 m2/g) which is one of the crucial factors to increase the photocatalytic activity. The loading of molybdenum enhanced the immobilization of carriers that facilitated the photo-oxidation process and suppressed the electron-holes recombination (from 800 counts to 200 counts) as confirmed by the PL spectroscopy. The photocatalytic activity of these catalysts were evaluated by studying the photodegradation of Methylene blue (MB) under sunlight in standard conditions (1 sun, 1 atm). The synergistic effect of inclusion of Erbium Oxide and loading of molybdenum in titania-Erbium Oxide composite enhanced the photodegration efficiency from 13.2% to 75 %. The photocatalytic activities were in order of Mo@TiO2–Er2O3 > Mo@TiO2 > TiO2–Er2O3 > TiO2. These modifications also improved the conductivity of titania (σ = 4.43 × 10−4 Sm−1 to σ = 5.31 × 10−4 Sm−1) that was confirmed by Hall effect. These results supported the effectiveness of titania-modified composite for the degradation of industrial textile dye wastewater under sunlight and can be used for an optoelectronics applications.

The Biosynthesis of Nickel Oxide Nanoparticles: An Eco-Friendly Approach for Azo Dye Decolorization and Industrial Wastewater Treatment

Wastewater is one of the major concerns for agriculture, and the composition of wastewater depends on its origin. Generally, industrial wastewater consists of azo dyes and heavy metals that contaminate the food chain. In this study, nickel oxide nanoparticles (NiO-NPs) were biosynthesized from Shewnella spp. and characterized by UV–visible spectroscopy (UV–vis), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Azo dye decolorization indicated that NiO-NPs decolorize methylene blue (MB) (82.36%), Congo red (CR) (93.57%), malachite green (MCG) (91.05%), reactive black 5(RB5) (55.17%), reactive red-II(RR-II) (55.45%), and direct blue-I(DB-I) (59.94%) at a dye concentration of 25 mg L−1 after 4 h of sunlight exposure. Additionally, the rate of decolorization was also examined for a 50 mg L−1 concentration of dye. In order to investigate the photocatalytic potential of NiO-NPs, different dyes were also subjected to static and shaking conditions for dye decolorization. The treatment of industrial wastewater with NiO-NPs showed a significant reduction in pH from 8.5 to 6.1, EC (48.38%), chemical oxygen demand (49.24%), total dissolved solids (67.05%), sulfates (52.5%), and phosphates (49.49%). The results of this study indicated that biosynthesized NiO-NPs are an attractive choice for azo dye degradation and industrial wastewater treatment, and they can help save the depleted natural resources of water for agricultural purposes.

Poloxamer 407 Combined with Polyvinylpyrrolidone To Prepare a High-Performance Poly(ether sulfone) Ultrafiltration Membrane.

At present, the design and fabrication of polymer membranes with high permeability and good retention ability are still huge challenges. In this study, the commercial Poloxamer 407 (Pluronic F127) is selected as a multifunctional additive, and polyvinylpyrrolidone is used as a pore-forming agent to modify the poly(ether sulfone) membrane by liquid-liquid phase conversion technology to prepare an ultrafiltration membrane with excellent performance. The hydrophobic poly(propylene oxide) segment in Poloxamer 407 guarantees that this copolymer can be firmly anchored to the poly(ether sulfone) matrix, and the hydrophilic poly(ethylene oxide) segments in Poloxamer 407 impart a stronger hydrophilic nature to the modified membrane surface. Therefore, the permeability and hydrophilicity of the modified membrane are significantly improved and the modified membrane also has good stability. When the amount of Poloxamer 407 added to the casting solution reached 0.6 g, the water flux of the modified membrane was as high as 368 L m-2 h-1, and the rejection rate of bovine serum albumin was close to 98%. In the test to isolate organic small molecule dyes, the retention rate of the modified membrane to Congo red is 94.27%. In addition, the modified membrane shows an excellent water flux recovery rate and antifouling ability. It performs well in subsequent cycle tests and long-term membrane life tests and can be used repeatedly. Our work has resulted in poly(ether sulfone) membranes with good performance, which show great potential in the treatment of biomedical wastewater and the removal of industrial organic dye wastewater, it provides ideas for the development and application of amphiphilic polymer materials.

Boron Bifunctional Catalysts for Rapid Degradation of Persistent Organic Pollutants in a Metal-Free Electro-Fenton Process: O2 and H2O2 Activation Process.

Metals usually served as the active sites of the heterogeneous bifunctional electro-Fenton reaction, which faced the challenge of poor stability under acidic or even neutral conditions. Exploring a metal-free heterogeneous bifunctional electro-Fenton catalyst can effectively solve the above problems. In this work, a stable metal-free heterogeneous bifunctional boron-modified porous carbon catalyst (BTA-1000) was synthesized. For the BTA-1000 catalyst, the yield of H2O2 (294 mg/L) significantly increased. The degradation rate of phenol by BTA-1000 (0.242 min-1) increased by an order of magnitude, compared with the porous carbon catalyst (0.0105 min-1). The BTA catalyst could rapidly degrade industrial dye wastewater, and its specific energy consumption was 5.52 kW h kg-1 COD-1, lower than that in previous reports (6.38-7.4 kW h kg-1 COD-1). DFT and XPS revealed that C═O and -BC2O groups jointly promoted the generation of H2O2, and the -BCO2 group played dominant roles in the generation of •OH because the oxygen atom near the electron-giving groups (-BCO2 group) facilitated the formation of hydrogen bond and H2O2 adsorption. This work gained deep insights into the reaction mechanism of the boron-modified porous carbon catalyst, which helped to guide the development of metal-free heterogeneous bifunctional electro-Fenton catalysts.

Treatment of textile waste water using activated carbon method

The textile industry extensively uses chemicals to dye fabrics, resulting in significant water pollution. The chemicals mix with water and harm the aquatic ecosystem. As a consequence, untreated wastewater from textile industries is discharged, posing a threat to water quality and human health. Several methods exist for treating such wastewater, including chemical and biological processes, and significant developments have been made in managing these wastewaters sustainably and recovering resources from them. Currently, there is a growing shift towards sustainable management of such wastewater, with a focus on resource recovery. This paper explores the most cost-effective methods for treating dye industry wastewater, specifically through filtration techniques. An experimental prototype was developed that utilized a three-layer filtration system composed of natural elements like coconut shell and coir, fine and coarse aggregates, and activated carbon to treat dyed wastewater. The results were compared with pre-treatment and post-treatment samples.

A Phytochemical Approach to the Removal of Contaminants from Industrial Dyeing Wastewater

This study investigates the influence of photoperiod and wastewater concentration on the growth of microalgae and cyanobacteria for the removal of environmentally significant parameters (COD, BOD, Cr, Fe, color, chlorides, nitrogen compounds, and phosphates) from dyeing wastewater. A two-factor central composite design with surface response was employed, involving two algae species (Chlorella and Scenedesmus sp.) and two cyanobacteria species (Hapalosiphon and Oscillatoria sp.). The findings indicated that extended photoperiods (>13 h) and higher wastewater concentrations (70–80% v/v) enhanced biomass production across all strains. However, Hapalosiphon and Chlorella sp. (1.6 and 0.45 g/L) exhibited better tolerance to the wastewater’s high toxicity, resulting in higher biomass concentrations and improved COD and BOD removal by Hapalosiphon sp. (75% and 80%, respectively). Further analysis of the obtained biomass revealed their potential applications. Among the cyanobacteria, Hapalosiphon sp. synthesized the highest concentrations of total proteins and lipids (38% and 28% w/w, respectively), while Oscillatoria sp. displayed a high protein content (42% w/w). In contrast, the algae demonstrated a strong propensity for storing substantial quantities of total carbohydrates (65% and 57% w/w for Scenedesmus and Chlorella sp., respectively). These results signify the feasibility of cultivating photosynthetic microorganisms in industrial dyeing wastewater as a sustainable source of nutrients for targeted metabolite production.

Grafted natural melanin κ-carrageenan hydrogel bead adsorbents: New strategy for bioremediation of cationic dye contamination in aqueous solutions

Pollution of water resources has become a global environmental problem, and the massive discharge of high-color printing and dyeing wastewater has caused serious harm to the natural environment. In this work, we have used repeated alkali solubilization and acid precipitation for an agricultural and forestry by-product, bilberry kernel shells, to obtain Mountain apricot shell Melanin (Mas-Mel), which can be used for the adsorption of cationic dyes. By graft copolymerization with a natural sugar-based polymer, κ-carrageenan (κCA), in a mild manner, we have prepared the adsorbent, Mountain apricot shell Melanin /κ-carrageenan (Mas-Mel/κCA) hydrogel beads, which were physically and chemically analyzed using a variety of spectroscopic and microscopic techniques. The optimum conditions for methylene blue (MB) adsorption and malachite green (MG) on Mas-Mel/κCA hydrogel were: contact time 150 min, adsorbent dose 60 mg, pH 6–7. The results of the adsorption tests followed the Pseudo-second order kinetics (R2 = 0.97 and 0.95), and the maximum adsorption capacity of MB and MG based on the Langmuir isotherm model was 48.63 mg/g and 37.84 mg/g, respectively. In addition, the prepared hydrogel beads still exhibited a high reusability and removal rate (∼50 %) after three consecutive 400-minute cyclic adsorption-resolution cycles. Our results may provide a new strategy for the development of green bio-based adsorbent materials and industrial dye wastewater treatment.

Biowaste derived UV–Visible-NIR active Z-scheme CaO/MoS2 photocatalyst as a low-cost, waste-to-resource strategy for rapid wastewater treatment

There is a need for industries to adopt greener strategies to minimise the environmental impact and overuse of natural resources. In the light of alarming environmental conditions, there is an expanding and progressing centre around the concept of waste to resource strategy. With this inspiration, a low-cost marine biowaste-based CaO/MoS2 photocatalyst synthesized by ball milling is proposed with a viable green route for water remediation. The mass ratio of CaO and MoS2 were optimized for the photocatalytic reduction of cationic methylene blue (MB) as a probe dye and an actual industrial dye wastewater. It was found that 45CaO/55MoS2 (45-CaMo) outperformed all the proportions including the conventionally popular TiO2. 70% of MB got discoloured in 10 min of exposure to natural sunlight following Langmuir-Hinshelwood model with a rate constant of 0.064 min−1 and exhibiting good photo-stability. The morphology and crystallinity were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). UV–Visible-NIR spectroscopy and calculations reveal the activity of the synthesized photocatalyst in UV, visible and IR regions with a direct Z-scheme mechanism as its probable charge modulation technique. This work offers new perspectives and directions for future research using waste-derived resources and renewable energy.

Efficient removal of cationic dye using ZIF-8 based sodium alginate composite beads: Performance evaluation in batch and column systems

The environmental and health risks associated with dye contamination in water sources are alarming. Recently, researchers have been focusing on developing an innovative and susceptible solution using composite beads that effectively combat this issue. In this paper, beads were synthesized using a sodium alginate (SA) and zeolitic imidazolate framework-8 (ZIF-8) through a simple dipping process. Several characterization tests were performed including XRD, FTIR, BET, TGA, and SEM-EDX. The SEM images confirmed that SA effectively coated the cubical structure of the ZIF-8, ensuring optimal performance. The efficiency of the resulting SA@ZIF-8 composite beads was tested on both synthetic malachite green dye and real industrial wastewater samples using batch and fixed bed column reactors. The findings revealed that maximum adsorption of 95.5% was achieved at pH 6 in 120 min of reaction time. FTIR and SEM analysis also confirmed the adsorption of MG dye onto the beads. The Freundlich isotherm model (R2 > 0.99) has a better fit than the Langmuir (R2 > 0.96) for describing the adsorption process. The PSO model predicted the kinetics of the system, whereas the intraparticle diffusion study supported the system's mechanistic analysis. Furthermore, the study also investigated the efficacy of the beads in treating real wastewater effluent samples collected from the dye industry. Overall, using sodium alginate-coated ZIF-8 beads was found to have many advantages over powdered ZIF-8, including higher selectivity, stability, reusability, and practicality, making them a promising alternative for adsorption applications. Therefore, these composite beads have the potential for the removal of the dye from wastewater, which could be widely applied in various industries.

Lead-free and highly-stable double perovskite Cs2SnClXI6-X microcrystals for efficient photocatalytic degradation

In order to protect water bodies and prevent water pollution, the direct use of clean solar energy to degrade the organic dyes in industrial wastewater into innoxious products is a potential strategy and a trending topic. Recently, the lead halide perovskites have been intensively investigated as photocatalysts on account of their unique photoelectric properties. Unsatisfactorily, the lead toxicity and instability of these materials cause irreversible harm to the ecology and low long-term degradation efficiency, limiting their practical applications. For the first time, lead-free double perovskite Cs2SnClXI6-X microcrystals were prepared by solution supersaturation recrystallization method for the photocatalytic degradation of Sudan Red III. The optical band gaps of the Cs2SnClXI6-X microcrystals were adjustable from 4.48 to 1.34 eV upon halogen regulation, while the photodegradation performance of Cs2SnCl4.1I1.9 was even much higher than the recently reported composite photocatalysts under similar conditions. Furthermore, the recycling and storage experiments demonstrated the reusability and excellent environmental stability of the as prepared Cs2SnClXI6-X microcrystals. Based on the results of the free radical trapping tests and electron paramagnetic resonance measurements, the mechanism for the photocatalytic degradation process were discussed in details.

Physiological and transcriptome profiling of Chlorella sorokiniana: A study on azo dye wastewater decolorization

Over decades, synthetic dyes have become increasingly dominated by azo dyes posing a significant environmental risk due to their toxicity. Microalgae-based systems may offer an alternative for treatment of azo dye effluents to conventional physical-chemical methods. Here, microalgae were tested to decolorize industrial azo dye wastewater (ADW). Chlorella sorokiniana showed the highest decolorization efficiency in a preliminary screening test. Subsequently, the optimization of the experimental design resulted in 70% decolorization in a photobioreactor. Tolerance of this strain was evidenced using multiple approaches (growth and chlorophyll content assays, scanning electron microscopy (SEM), and antioxidant level measurements). Raman microspectroscopy was employed for the quantification of ADW-specific compounds accumulated by the microalgal biomass. Finally, RNA-seq revealed the transcriptome profile of C. sorokiniana exposed to ADW for 72 h. Activated DNA repair and primary metabolism provided sufficient energy for microalgal growth to overcome the adverse toxic conditions. Furthermore, several transporter genes, oxidoreductases-, and glycosyltransferases-encoding genes were upregulated to effectively sequestrate and detoxify the ADW. This work demonstrates the potential utilization of C. sorokiniana as a tolerant strain for industrial wastewater treatment, emphasizing the regulation of its molecular mechanisms to cope with unfavorable growth conditions.

An optimized backpropagation neural network models for the prediction of nanomaterials concentration for purification industrial wastewater

In this paper, an optimized backpropagation neural network (BPNN) prediction models have been proposed to estimate the concentration of titanium dioxide (TiO2) nanomaterials required for the removal of Acid Black 24 dye, a type of textile dye, from industrial wastewater. The research gap addressed in this study lies in the investigation of various optimization algorithms for BPNN models and their profound impact on the accuracy of nanomaterial concentration predictions, thus contributing to the advancement of nanotechnology-based wastewater treatment research and its practical applications in industrial settings. Although several studies have predicted the amount of nanomaterial needed to degrade the dyes in industrial wastewater using BPNN, few have investigated the effects of optimized BPNN and how greatly the amount of degradation can vary. Therefore, six different optimization algorithms, including genetic algorithms (GAs), ant colony optimization (ACO), particle swarm optimization (PSO), evaluation strategy (ES), biogeography-based optimization (BBO), and population-based incremental learning algorithm (PBIL), are applied to optimize and evaluate the BPNN models. Experimental data obtained from chemical laboratory experiments are used to train and test the models, with different experiments conducted for various factors like TiO2, H2SO4, NaIO4, K2S2O8, dye, and silver nitrate. The performance of the optimized BPNN models is assessed using metrics such as mean squared error (MSE), root means squared error (RMSE), and R-squared (R2). The results demonstrate the effectiveness of the proposed models, with ACO yielding the best outcomes across all models. The R2 values for the TiO2, H2SO4, NaIO4, and K2S2O8 models after optimization indicate perfect predictions, whereas the R2 values before optimization ranged from 0.888 to 0.984. PSO performs well for most models except for K2S2O8, GA improves most models except for the silver nitrate model, ES enhances only the Dye model, and PBIL does not affect the TiO2 model. Overall, the optimized BPNN models exhibit impressive accuracy in estimating the TiO2 concentration required for removing Acid Black 24 dye from industrial wastewater.