Dye Pollutants Research Articles

S-scheme mechanism in the TiO2/Cu2O@Cu system toward selective degradation of an electron-rich dye pollutant under solar light

This research aims to reach a selective nanocomposite based on Cu and TiO2 nanoparticles (NPs) through a sol–gel followed by chemical reduction. Various methods such as XRD, SEM, TEM, HRTEM, BET, Raman, FTIR, DRS, XPS and PL analysis were used to characterize the prepared NPs. The reduced nature of Cu in nanocomposite was evidenced by its X-ray photoelectron spectral characteristics and its HRTEM image. Due to the presence of Cu NPs, light absorption in solar radiation by nanocomposite was considerably enhanced and caused more efficient charge carriers separation. A CCD was used to evaluate the photoactivity of the solar-driven photocatalyst by degrading methylene blue (MB) as a single model electron-rich organic pollutant. In optimal conditions, the highest photocatalytic activity reached 95.64 %. In this study, band structure and reactive species scavenging results confirmed an S-scheme mechanism for charge carrier transfer during photodegradation. The plasmonic S-scheme TiO2/Cu2O@Cu heterojunction photocatalyst exhibited remarkably strong photocatalytic selectivity toward MB in binary mixtures of MB with eosin B and rhodamine B. A preference for degradation of MB over safranin (Saf) is confirmed by the faster degradation rate of MB than that of Saf. S-scheme mechanism, Cu doping and dye sensitization all contributed to outstanding selective photodegradation performance.

Magnetically retrievable Nb2O5/CoFe2O4 photocatalysts for degradation of crystal violet dye pollutant under solar irradiation

Electrochemical oxidations of complex toxic dyes have been widely investigated on metal–organic-framework, which are often limited by high energy demand or deactivation of organic support. Here, the potential application of a magnetically retrievable solar-driven nanocomposite of Nb2O5-CoFe2O4 for removing crystal violet was explored and compared under simulated solar radiation (60.82 mW/cm2) or darkness. In the synthesized composite, Nb2O5 exists as a dispersed phase on CoFe2O4, forming a core–shell structure. Both the optical and magnetic behaviour of Nb2O5-CoFe2O4 were extensively investigated to optimize their photocatalytic applications in the removal of crystal violet.The nanocomposite was strongly ferromagnetic even after loading Nb2O5 on cobalt ferrite. The photocatalytic performance of the composites showed a positive relationship with the Nb2O5 content, where optimum degradation was observed with 50 % Nb2O5-CoFe2O4. The ferromagnetic property was exploited to retrieve the catalyst from the water after the purification process. This study demonstrates the facile method for the novel Nb2O5-CoFe2O4 synthesis and elucidates its high potential in sustainable remediation of complex toxic dyes using solar energy and as reusable magnetic recovery in aqueous systems. Also, 50 % Nb2O5-CoFe2O4 has been implemented inwater purification processes and pollutant degradation, thereby definitely amplifying the prospects for sustainable development of this research work.

Post-synthetic modification of zirconium-based metal-organic frameworks for enhanced simultaneous adsorption of heavy metal ions and organic dyes

Heavy metal and dye pollution pose a serious threat to human health and ecology, and there is an urgent need to develop novel adsorbent materials for wastewater treatment. In this study, a novel functionalized zirconium-based MOF UiO-66-Gd was prepared by a post-synthetic modification strategy and used for the simultaneous removal of Pb2+, Cu2+ and methylene blue (MB) from wastewater. UiO-66-Gd retained the crystalline structure and morphological features before modification. The specific surface area reached 574.94 m2/g, which can provide abundant active sites for adsorption. The effects of several factors on the adsorptive performance of UiO-66-Gd were investigated by batch adsorption experiments. The adsorption of Pb2+ by UiO-66-Gd reached the adsorption equilibrium in only 5 min. The theoretical maximum adsorption capacities for Pb2+, Cu2+ and MB were 833.33, 354.61 and 564.91 mg/g, respectively. In addition, UiO-66-Gd has excellent anti-interference and regeneration properties with potential for practical applications. Competition adsorption experiments showed that UiO-66-Gd had the greatest affinity for Pb2+. The adsorption of UiO-66-Gd on Pb2+ and Cu2+ was mainly through electrostatic interactions and chelation, and on MB mainly through electrostatic interactions, π-π interactions and hydrogen bonding. Overall, UiO-66-Gd has great potential for application in the removal of Pb2+, Cu2+ and MB.

Methylene blue adsorption on Y-zeolite as a nano-porous adsorbent: equilibrium and kinetic studies

ABSTRACT The elimination of dye pollutants from industrial wastewaters, notably from sectors such as textiles and dyeing, remains a pivotal aspect of pollution mitigation endeavours. This research introduces an innovative strategy employing Y zeolite as a nano-porous adsorbent for eliminating methylene blue (MB), a prevalent cationic dye. Y zeolite was synthesised via hydrothermal technique. Through methodical experimentation, the impact of temperature, contact time, concentration, pH and adsorbent quantity on removal efficiency were examined with optimal conditions achieving 93.83% MB removal. The synthesised Y zeolite underwent characterisation utilising diverse techniques, including SEM, TEM, XRD, BET, and FTIR, which elucidated the structural and chemical characteristics. The surface area and pore diameter of Y zeolite were determined to be 229.1 m2/g and 20.3 Å, respectively. Utilisation of Response Surface Methodology (RSM) using design expert software facilitated the exploration of influential parameters, such as pH, temperature, contact time, adsorbent quantity, and MB concentration. The optimal conditions of pH = 7, temperature = 43°C, contact time = 85 min, adsorbent dosage = 0.5 g/L, and initial concentration = 30 ppm were obtained. Furthermore, reusability and durability of Y zeolite through multiple cycles of MB adsorption was assessed, revealing a retained efficiency of ~ 70% after 5 consecutive cycles. Kinetic studies confirmed pseudo-2nd-order model, emphasising chemisorption as the rate-limiting step. Equilibrium data fitting to the Langmuir isotherm highlighted the homogeneity of active adsorption sites on the zeolite surface, emphasising a high adsorption capacity. In conclusion, this study offers a promising solution for the removal of MB from aqueous solutions using Y zeolite as a nano-porous adsorbent. The findings underscore the importance of zeolite’s porosity and surface characteristics in enhancing adsorption efficiency, providing valuable insights for future applications in water treatment and environmental remediation efforts. This research showed that Y Zeolite is effective, low cost, eco-friendly, and can be regenerated as an adsorbent to eliminate MB from aqueous systems.

Harnessing the hidden environmental power of Bjerkandera adusta laccase: Sustainable production, green immobilization, and eco-friendly decolorization of mixed azo dyes

This research unveils the untapped potential of laccase, derived from the Bjerkandera genus, utilizing it in an immobilized system aimed at detoxifying harmful azo dye effluents from the textile industry, thus contributing to environmental protection. Marking a pioneering achievement, we recorded the highest laccase activity at 94.52 U/g cultivating B. adusta's mycelium on brewer's spent grain, enhanced with lignocellulosic waste, under meticulously optimized conditions −2.69 g of alkali-pretreated beech sawdust, 0.91 g of cypress cone, and 8-day incubation period. The harvested laccase was subjected to an immobilization process on alkali-pretreated beech sawdust, where, through optimization, we established the ideal conditions (30 mg of carrier, pH 7, and 3.5 h), achieving an immobilization efficiency of 72.24% with a residual activity of 57.64%. Remarkably, both free and immobilized forms of the B. adusta TMF1 laccase enzyme demonstrated formidable efficacy in decolorizing a mix of three distinct azo dyes (Orange G, Eriochrome Black T, and Congo Red), eliminating over 63% of the coloration within just 30 min. The immobilized laccase showed consistent performance across four decolorization cycles. Moreover, the breakdown products of the azo dye mix were analyzed using the HPLC method, complemented by evaluations of potential antimicrobial activity, phytotoxicity and cytotoxicity, revealing a non-toxic composition without cytotoxicity, highlighting the process's safety for environmental release. The significance of this research is reflected in the distinguished construction of a green biocatalyst acting as a stable and time-efficient in remediation of targeted azo dye pollution from the textile industry following the principles of circular economy.

Constructing p-n heterojunction in CoO@TiO2 photocatalytic material to enhance the performance of catalytic degradation of Rhodamine B

Traditional Fenton reactions suffer from slow reaction rates and energy wastage degrade dye contaminant. By constructing a heterojunction interface between quantum dots and titanium dioxide, a CoO@TiO2 photocatalyst is prepared to extend the photoresponse range to longer wavelengths. Under infrared light irradiation, RhB is degraded by over 97 % after 120 min. CoO@TiO2 possesses a large surface area, loaded with a substantial amount of quantum dots, forming a p-n heterojunction, significantly enhancing the photocatalytic rate. This study provides a new approach for the efficient preparation of photocatalysts for the degradation of organic dye pollutants.

Lignin-Derived Sustainable Nano-Platforms: A Multifunctional Solution for an Efficient Dye Removal.

In contrast to conventional non-biobased adsorbents, lignin emerges as a cost-effective and environmentally benign alternative for water treatment. This study identifies unexpected and unpredicted multifunctional properties of lignin nanoparticles (LNPs). LNPs, which are prepared by simple physical processes, demonstrated for the first time to behave as multifunctional materials able to adsorb and photodegrade methylene blue (MB) in aqueous medium upon UV irradiation. Furthermore, the synthetic approach adopted to synthesize LNPs - and therefore their surface properties - strongly affects their performances. More specifically, LNPs obtained by solvent-antisolvent nanoprecipitation (SLNPs) show the highest MB adsorption properties (98 % removal), reaching a maximum adsorption capacity of 43.0 mg g-1, and the fastest adsorption kinetics with respect to other lignin-based adsorbents. Conversely, hydrotropic LNPs (HLNPs) exhibit exceptional photocatalytic activity, resulting in 98 % MB degradation over 6 hours of UV irradiation, combined with the ability to be easily recycled and reused. The present effort paves the way for the use of LNPs as efficient multifunctional materials able to perform concurrently adsorption and photocatalytic degradation of dye pollutants, toward the creation of a sustainable biobased water treatment platform.

Standalone Highly Efficient Graphene Oxide as an Emerging Visible Light-Driven Photocatalyst and Recyclable Adsorbent for the Sustainable Removal of Organic Pollutants.

Carbon-based nanostructures are promising eco-friendly multifunctional nanomaterials because of their tunable surface and optoelectronic properties for a variety of energy and environmental applications. The present study focuses on the synthesis of graphene oxide (GO) with particular emphasis on engineering its surface and optical properties for making it an excellent adsorbent as well as a visible light-active photocatalyst. It was achieved by modifying the improved Hummers method through optimizing the synthesis parameters involved in the oxidation process. This controlled synthesis allows for systematic tailoring of structural, optical, and surface functionality, leading to improved adsorption and photocatalytic properties for the sustainable removal of organic pollutants in water treatment. Several spectroscopic and microscopic characterization techniques, such as XRD, SEM, Raman, UV-visible, FTIR, TEM, XPS, BET, etc. were employed to analyze the degree of oxidation, surface chemistry/functionalization, morphological, optical, and structural properties of the synthesized GO nanostructures. The analyses showed excellent surface functionality with surface active sites for better adsorptive removal and a tunable band gap from 2.51 to 2.76 eV exhibiting excellent natural sunlight activity (>99%) for photocatalytic removal of the organic pollutant. Various adsorption isotherms have been studied with excellent adsorption capability (Qmax = 454.54 mg/g) as compared to the literature. The study introduces GO both as a proficient stand-alone (sole) nanoadsorbent as well as a nanophotocatalyst for the efficient removal of organic dye pollutants in water treatment. Additionally, the article highlights the sustainable solar light-induced green chemistry aspects of GO as an excellent recyclable adsorbent as a result of its self-cleaning ability under natural sunlight, demonstrating its potential in real eco-friendly environmental and practical applications.

Chitosan-derived activated carbon/chitosan composite beads for adsorptive removal of methylene blue and acid orange 7 dyes

In this study, a chitosan/activated carbon composite was developed for the sustainable removal of dye pollutants from activated carbon derived from chitosan. First, chitosan was converted into chitosan-derived activated carbon (C-AC) with a large Brunauer-Emmett-Teller (BET) surface area of 2428 m2/g through carbonization using a potassium hydroxide (KOH) chemical activator. To enable simple separation from contaminated water and sustainable use in the adsorption process, the generated C-AC was incorporated into a bead-type, stable three-dimensional chitosan polymer network structure. The prepared C-AC-incorporated chitosan beads showed excellent adsorption capacity for the anionic acid orange 7 (AO) (511.38 mg/g) and the cationic methylene blue (MB) (413.08 mg/g). In addition, it maintained structural stability even in various pH environments and could be easily separated from contaminated water. The C-AC-incorporated chitosan beads showed excellent reusability and durability, maintaining at least 82% and 86% removal efficiencies for AO and MB dyes even after five reuses. This study suggests the potential use of chitosan as an eco-friendly adsorbent that can be utilized simultaneously as an activated carbon precursor and as a matrix for robust bead-like polymer composites.

Photocatalytic degradation of toxic basic blue 41 and reactive orange M2R dyes using green synthesized zinc oxide nanoparticles

Zinc oxide nanoparticles (Cm-ZnO NPs) were synthesized to eliminate organic dye pollutants from textile dye effluents. The present study reports Cucumis maderaspatanus L. leaves utilized as a green reducing/stabilizing agent for Cm-ZnO NPs synthesis. The nanoparticles underwent thorough analysis using techniques such as XRD, UV–vis, TEM, and FT-IR. Photocatalytic degradation of toxic basic blue 41 (BB41) and reactive orange M2R (ROM2R) dyes using Cm-ZnO NPs, showed a degradation rate of 97.69 % and 94.30 % respectively under optimized conditions. The kinetics of photocatalytic degradation of BB41 and ROM2R dyes followed first-order kinetics. The scavenger studies were conducted to identify the photogenerated reactive species involved in dye degradation. The singlet oxygen (1O2) and hydroxyl radicals (●OH) are mainly responsible for the degradation of BB41 and ROM2R dye respectively. LC-MS analysis was used to identify the photocatalytic degraded products, and ECOSAR software assessed their toxicity. The recyclability was performed up to four cycles and the stability of Cm-ZnO NPs was confirmed by XRD analysis. Thus, the as-synthesized Cm-ZnO NPs are suitable for industrial textile wastewater treatment.

Photocatalytic degradation of rhodamine B dye pollutants by Fe3O4/SiO2 core-shell magnetic nanocomposite functionalized with TiO2.

Significant efforts have been dedicated to creating recyclable and efficient methods for treating waste dyes, including rhodamine B (RhB). Nevertheless, challenges such as complex operational techniques, high costs, energy consumption, and inefficacy in dye removal persist. Here, the synthesis and application of TiO2/Fe3O4/SiO2 for photocatalytic degradation of RhB dye pollutants have been explored. This research was initiated with magnetite (Fe3O4) synthesis using the coprecipitation method, followed by silica (SiO2) extraction from rice husk waste using the sol-gel process, and a hydrothermal method for synthesizing titanium dioxide (TiO2) and TiO2/Fe3O4/SiO2 nanocomposite. The crystalline structure of TiO2/Fe3O4/SiO2 was obtained with Fe3O4 as the core, while TiO2 and SiO2 as the shell. The particle size analysis showed the nanosize of TiO2/Fe3O4/SiO2 (1.04 ± 0.46nm). TiO2/Fe3O4/SiO2 nanocomposite boasts a high surface area of 48.025 m2/g, 2.2 times higher than unmodified TiO2. This nanocomposite also displayed paramagnetic properties with a saturation magnetization of 9.117emu/g, facilitating easy separation in photocatalytic applications. The photocatalytic activity of TiO2/Fe3O4/SiO2 exhibited effectively degraded RhB, achieving a degradation rate of 53.58% and an excellent rate constant of 0.7303min-1. The RhB photodegradation in this study requires a moderate irradiation time (60min), uses only a tiny amount of photocatalyst (100mg), and does not need additional chemicals. Moreover, this study has another advantage of utilizing rice husk as a silica source, offering an eco-friendly and sustainable approach.

Dye Removal From Tannery Wastewater Utilizing Footwear Waste: A Sustainable Approach

ABSTRACTWaste‐to‐3R (reduce, reuse, and recycle) is a promising mass balance approach in the leather sector for addressing the current challenge of overproduction of rubber sole waste in the footwear industry and dye pollution in tanneries. In this study, low‐cost charcoal derived from discarded natural rubber (NR) soles was effectively employed to remove anionic and cationic dyes from a model tannery dye solution, aligning with mass balance approaches in the leather sector. Discarded rubber charcoal (DRC) was prepared at 350°C using a self‐fabricated pyrolytic cell. The resulting charcoal was then dried, ground, and separated through 40‐mesh size lab‐scale sieves, and it was subsequently employed for the removal of dyes from tannery wastewater. The dye removal performance was optimized by adjusting parameters such as dosage, pH, contact time, and concentration. The maximum adsorption capacity and removal efficiency of the anionic acid dye (AD) were found to be 158.22 mg/g and 88.39% at pH 1, respectively, while those of the cationic methylene blue dye were 166.18 mg/g and 85.53% at pH 12, respectively, between 15 and 30 min, depending on the DRC conditions. Fresh charcoal and dye‐loaded charcoal were characterized through Fourier transform infrared spectroscopy, x‐ray diffraction, Brunauer–Emmett–Teller, scanning electron microscope (SEM), and transmission electron microscope with Energy‐Dispersive X‐ray (EDX) Spectroscopy for respective functional groups and morphology studies, and zeta potential measurements were employed to characterize the charcoal surface charge. The SEM image revealed that the shape of the DRC particles resembles a honeycomb structure, with an average size of 573.56 µm. The adsorption kinetic study indicates that the Freundlich isotherm model and pseudo‐second‐order kinetics were well‐fitted for dye removal in this study. The charcoal exhibited robust stability, retaining its capacity of 57.42 mg/g of AD and 44.94 mg/g of MB dye after four reuse cycles. This resilience was observed in treatment with various desorption agents, including HCl, CH3COOH, NaOH, and C2H5OH. The findings of this study suggest that NR‐derived charcoal could be used as a successful substitute for commercial activated carbon in wastewater treatment to get rid of the acid and basic dyes of the leather industry. Based on the observed results, a plausible mechanism was also proposed.

Highly Porous Multiwalled Carbon Nanotube-Foam Composite for Batch Adsorption Performances of Dyes.

Treatment of dye pollutants prior to their release into the environment remains a formidable challenge, persisting as a longstanding issue. This study focuses on the development of a multiwalled carbon nanotube-foam (MWCNT-foam) composite through low-temperature chemical fusion (LTFC), resulting in a composite with a remarkably high accessible surface area (>475 m2 g-1). The MWCNT-foam composite exhibits a three-dimensional porous structure and demonstrates a notable affinity for organic dye adsorption. The efficacy of this composite was evaluated against various cationic dyes such as Methylene blue (MB) and Crystal Violet (CV) as well as anionic dyes such as Congo red (CR) and Eriochrome black T (EB), and the composite showed removal rates exceeding 99%. Furthermore, the study delved into the impact of the initial dye concentration, adsorbent dosage, kinetics, and other factors on the performance of the MWCNT-foam composite. The adsorption process achieved equilibrium in 10 min and strongly correlated with the pseudo-second-order kinetic model and Langmuir isotherm. The maximum adsorption capacity of MWCNT-foam for MB, CV, CR, and EB was found to be 168.63, 147.49, 99.50, and 93.11 mg g-1, respectively. In order to showcase the potential of this material for continuous adsorption, a specialized cartridge was designed and employed to treat dye solutions, demonstrating the feasibility of continuous mode adsorption.

Drastic enhancement by in situ CNTs growth of carbon felt activity toward the electrodegradation of an azo dye

A new composite material has been developed for the electro-Fenton process to remove Acid Orange 7 (AO7), an azo dye pollutant, from wastewater. This material features the in situ growth of carbon nanotubes (CNT) at the interface of carbon felt/phenolic resin (CF/PR). Different CF/PR composite materials were manufactured by impregnation of an alcoholic phenolic resin/ferrocene solution on a carbon felt that was treated by acidic oxidation or not. The carbonization step under N2 atmosphere is necessary for the growth of the CNTs at the interface of the CF/PR composite. SEM observations show clearly the presence of CNTs at different levels of growth at the interface CF/PR. They also reveal that oxidizing carbon felts greatly boosts the CNT production in the composite (CF-oxy/CNT/PR). Raman spectroscopy, using the ID/IG ratio, confirmed these findings, matching the conductivity measurements. The formation of CNT via a ferrocene catalyst at the CF/PR interface notably enhanced the composite electrode's conductivity, especially when the carbon felts were oxidized. The elaborated composites were further used as cathodes to carry out the electro-Fenton (EF) process applied to the degradation of Acid Orange 7 (AO7) in the treated effluent. The discoloration of the AO7 solution was achieved in <15 min, demonstrating an effective treatment. In addition, the progress of AO7 mineralization was tracked through measurements of total organic carbon (TOC). Therefore, after 4 h of electro-Fenton treatment, a significant enhancement was evidenced with nearly a complete mineralization of 98 % compared to only 55 % achieved with the raw carbon felt (CF) material as electrode. As a result, the proposed method of modifying the CF/PR composite interface through CNT growth has improved their electrocatalytic activities, showcasing their promising potential for electrochemical applications.

A comprehensive analysis and exploration of the recent developments in the utilization of genetically modified microorganisms for the remediation of hazardous dye pollutants

Innovative and effective remediation techniques are required with regard to growing environmental concerns on hazardous dye pollutants emitted by the textile industries. The review explores on the recent developments in utilization of genetically modified organisms (GMO) for the dye removal. Through improved capacities and specificities towards dye pollutants, genetically modified organisms present a potential strategy towards achieving Sustainable Development Goal (SDG) No. 6 of the UN, focused on clean water and sanitation. The key findings show that genetic engineering methods, including recombinant DNA (rDNA) and CRISPR-Cas9 technologies, can increase the capacity of bacteria to degrade, metabolize, or immobilize dye pollutants, improving degradation efficiency from around 7%–65%. The enzymatic processes are identified as the primary mechanisms involved in dye compound degradation by genetically engineered microbes. The review emphasizes the use of genetic approaches for dye degradation, co-cultivation with native microbial communities, optimizing operational parameters like pH, temperature, and nutrient availability, and omics technologies for a deeper understanding of metabolic networks and regulatory mechanisms with the aim of leading future genetic advancements in dye remediation. The review discusses the practical feasibility and environmental safety challenges of using genetically engineered microbes in sustainable dye remediation, highlighting limitations and future insights.

Dual-function CoNi-LDH hollow porous spheres for morphology-driven adsorptive removal and photo-oxidative degradation of anionic dyes

The layered double hydroxides (LDHs) emerged as a class of low-cost potential adsorbents for organic pollutant separation, whereas the deep study of organic dye separation regulated by LDH hollow morphology under ambient conditions is still lacking. To address this gap, ZIF-67, Bulk-CoNi-LDH, and HPS-CoNi-LDH materials of different morphology and porosity were synthesized and investigated in the dye separation process. Methyl orange (MO), congo-red (CR), methylene blue (MB), and rhodamine B (Rhb) dyes were selected as model dye pollutants. The spectroscopic and structural analysis reveals the HPS-CoNi-LDH exhibits less-aggregated 2D nanosheets, high BET surface area of 163.2 m2/g, large pore size of 12.29 nm, greater positive surface charges (27.5 mV), superior optical (2.18 eV), and charge-separation capabilities as compared to Bulk-CoNi-LDH, Which provides potential sites for adsorptive and photo-degradation for anionic dyes under natural sunlight. Therefore, it achieves a remarkable removal efficiency of 92.6% for methyl orange (15 ppm) with a superior kinetic rate of 3.0×10−2 min−1 within 90 min, outperforming Bulk-CoNi-LDH and ZIF-67 having removal efficiency of 71.7% and 40.8%, and kinetic rate of 1.35×10−2 and 0.5×10−2 min−1, respectively. Poor removal efficiency and kinetic by ZIF-67 was mainly due to its smaller pore size (1.16 nm) and surface-confined charges (6.13 mV). Additionally, HPS-CoNi-LDH exhibits superb selectivity (at a ppm level) and excellent recyclability under ambient conditions. The mechanism of photo-catalytic reaction is discussed. These results delineate the hollow morphological LDH structure could be a worthy candidate for selective wastewater treatment and useful for sustainable conditions, which points the way to other crucial anionic micropollutant remediation.

Photocatalytic nanohybrid UV-light-driven PVDF/GO-NiFe@SiO2 membrane coupled with bentonite adsorption and ozonation process for a sustainable textile wastewater treatment

The textile industries face significant environmental challenges due to the presence of complex pollutant dyes in its wastewater, making it one of the world's major sources of industrial water pollution. Numerous studies have been employed to overcome this problem, including physical, chemical, and biological treatments. However, most of those methods still suffered to achieve higher dye removal performance. This study provides new insight regarding textile wastewater treatment containing indigo red as the main colorant by carrying out a hybrid process combining bentonite adsorption, ozonation, and photocatalytic membrane filtration. For the membrane, we propose a modified polyvinylidene fluoride (PVDF) membrane incorporated with graphene oxide (GO) and nickel-iron doped silica (NiFe@SiO2) photocatalyst, which is named PVDF/GO-NiFe@SiO2 membrane. The membrane was employed under different sets of filtrations (dark and under ultraviolet irradiation) to treat natural dye wastewater from textile industry effluent. Further improvement was achieved when UV light irradiation was subjected to the process. This sequential adsorption-ozonation-membrane process under UV exposure exhibited improved dye removal from 55.11 % to 97.22 %. The results show that the proposed hybrid process successfully improved the membranes' antifouling behavior, thus boosting the membranes' performance and durability. From a broader perspective, our work promotes new insights for the integration of other physical, chemical, and biological treatment methods to improve the performance and durability of membrane-based processes, particularly for dye wastewater treatment.

Reactive oxygen species and NOM-induced surface rejection guarantee effective removal of dye pollutants by cobalt-manganese bimetallic oxide loaded ceramic membrane activating peroxydisulfate

Developing high-efficient, environmental-friendly, stable catalytic membrane is of great significance for the removal of organic pollutants from natural water. Herein, the aim of this study was to fabricate ceramic membranes loaded with cobalt-manganese bimetallic oxides (Co–Mn-M) and evaluate their effectiveness and reaction mechanisms in activating peroxydisulfate (PDS) to degrade organic pollutants. The result showed that Co–Mn-M not only had exceptional effect on dye removal (91.36 %) through PDS activation, but also exhibited synergistic efficacy in mitigating membrane irreversible fouling during filtration. The superiority of the Co–Mn-M/PDS system could be attributed to two reasons. On the one hand, dual redox cycles of Co3+/Co2+ and Mn2+/Mn3+/Mn4+ and oxygen vacancy on membrane surface ensured the continuous activation of PDS to generate abundant reactive oxygen species including SO4•-, •OH, O2•-, and 1O2, among which SO4•- played a predominant contributor to dye degradation. On the other hand, the hydroxylation and carboxylation via radical oxidation could increase the energy barrier for natural organic matter (NOM) adhering to the membrane surface, thereby achieving a NOM-induced surface rejection for contaminants. Consequently, the Co–Mn-M/PDS system showed lesser energy consumption than conventional ceramic membrane filtration. In conclusion, this study presented a promising strategy for dye removal, ensuring the safe reclamation of water resources.

Unmodified Mg/Al layered double hydroxide clay with versatile and specific adsorption capacity over high spectrum type of harmful contaminants

The present study investigates the effectiveness of Mg/Al layered double hydroxide (MATclay) for adsorbing Congo Red dye (CR) from wastewater. MATclay was prepared using a cost-effective co-precipitation method at pH 9.5, ensuring both chemical and mechanical stability. The in-depth physico-chemical characterization of MATclay sample was performed using various techniques, including FE-SEM, FT-IR, XRD, DLS, BET surface area, Zeta potential, TEM, XPS, XAS, and TGA. Batch experiments were performed to evaluate the adsorptive performance under different conditions (30–100 mg/L initial concentration, 298–320 K temperature range, and 5–180 min contact time). The adsorption data fit best with the Langmuir model, indicating monolayer adsorption with a maximum capacity of 60.61 mg/g. Post-adsorption analysis with SEM, XRD, and TGA confirmed the interaction of CR with MATclay. Furthermore, the MATclay material was applied as potential adsorbent for other type of pollutants, namely cationic dye (Methylene Blue) and antibiotics (Metronidazole, Tetracycline, and Cefotaxime), the data obtained in this complementary study showing good results for the removal of Tetracycline and Cefotaxime antibiotics. Overall, MATclay demonstrates potential as an effective adsorbent for CR dye and other pollutants in wastewater treatment.

Green synthesis of magnetite iron oxide nanoparticles using Azadirachta indica leaf extract loaded on reduced graphene oxide and degradation of methylene blue

In the current arena, new-generation functional nanomaterials are the key players for smart solutions and applications including environmental decontamination of pollutants. Among the plethora of new-generation nanomaterials, graphene-based nanomaterials and nanocomposites are in the driving seat surpassing their counterparts due to their unique physicochemical characteristics and superior surface chemistry. The purpose of the present research was to synthesize and characterize magnetite iron oxide/reduced graphene oxide nanocomposites (FeNPs/rGO) via a green approach and test its application in the degradation of methylene blue. The modified Hummer's protocol was adopted to synthesize graphene oxide (GO) through a chemical exfoliation approach using a graphitic route. Leaf extract of Azadirachta indica was used as a green reducing agent to reduce GO into reduced graphene oxide (rGO). Then, using the green deposition approach and Azadirachta indica leaf extract, a nanocomposite comprising magnetite iron oxides and reduced graphene oxide i.e., FeNPs/rGO was synthesized. During the synthesis of functionalized FeNPs/rGO, Azadirachta indica leaf extract acted as a reducing, capping, and stabilizing agent. The final synthesized materials were characterized and analyzed using an array of techniques such as scanning electron microscopy (SEM)-energy dispersive X-ray microanalysis (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction analysis, and UV–visible spectrophotometry. The UV–visible spectrum was used to evaluate the optical characteristics and band gap. Using the FT-IR spectrum, functional groupings were identified in the synthesized graphene-based nanomaterials and nanocomposites. The morphology and elemental analysis of nanomaterials and nanocomposites synthesized via the green deposition process were investigated using SEM–EDX. The GO, rGO, FeNPs, and FeNPs/rGO showed maximum absorption at 232, 265, 395, and 405 nm, respectively. FTIR spectrum showed different functional groups (OH, COOH, C=O), C–O–C) modifying material surfaces. Based on Debye Sherrer's equation, the mean calculated particle size of all synthesized materials was < 100 nm (GO = 60–80, rGO = 90–95, FeNPs = 70–90, Fe/GO = 40–60, and Fe/rGO = 80–85 nm). Graphene-based nanomaterials displayed rough surfaces with clustered and spherical shapes and EDX analysis confirmed the presence of both iron and oxygen in all the nanocomposites. The final nanocomposites produced via the synthetic process degraded approximately 74% of methylene blue. Based on the results, it is plausible to conclude that synthesized FeNPs/rGO nanocomposites can also be used as a potential photocatalyst degrader for other different dye pollutants due to their lower band gap.