Dye Removal Research Articles

Unravelling the efficiency of CoAl-LDH / g-C3N4 nanosheets: Type-II heterojunction for photocatalytic hydrogen production and dye degradation under solar light irradiation

The generation of hydrogen fuel, and wastewater treatment according to solar-driven catalysis possesses considerable prospective for establishing a carbon-neutral and ecologically sound power infrastructure. Driven by this problem, we suggest in this study, adopting a simple impregnation method, a customized association of CoAl-LDH and graphitic carbon nitride (CN), a visible light active narrow and wide band gap semiconductors. Several characterization approaches were implemented to understand the CoAl-LDH@g-C3N4 (CACN) composites' physiochemical and optical features. The CACN hetero structural forms exhibited significantly improved solar light-induced photocatalytic H2 generation and dye pollutants decomposition in contrast with pristine materials. The most effective catalyst 5 wt% CoAl-LDH@g-C3N4 (5-CACN) generated the highest hydrogen (∼430.7 μmolg−1h−1), which is 11.9-fold H2 production efficiency compared with CN and depicted significant Brilliant black dye removal efficacy via photocatalytic degradation (up to ∼79%). This was primarily ascribed to the development of the Type-II CACN heterojunctions, which promoted the separation of charges and expanded the abundance of surface-active sites while absorbing the visible spectrum of solar light.

Bioremediation of textile wastewater using Bacillus cereus isolated from refinery site: Comparative analysis of free and immobilized cells systems

The textile industries consume a considerable amount of freshwater and discharge untreated or semi-treated pollutants to the environment. Azo dyes, generally employed in textile manufacturing industries, have a hazardous impact on the ecosystem. Incomplete treatment of wastewater containing azo dyes discharges into the aquatic system, which has recalcitrant and toxic properties. Hence, the need for cost-effective and high-performing technologies is essential. In this direction, bacterial degradation is considered an economically viable and efficient technique for the treatment of Active blue (AB) dye. Polyurethane foam (PUF) is a low-cost and hydrophilic material with a microporous structure, which offers an excellent surface-to-volume ratio. Hence, PUF was preferred for the immobilization of isolated bacterial species. For this, a dye-degrading gram-positive bacteria namely Bacillus cereus GS2 IIT (BHU) was isolated from the petroleum sludge. A comparative analysis between free and immobilized cell systems was carried out by varying the process parameters, i.e., batch time, pH, temperature, glucose concentration, and initial AB dye concentration. The corresponding optimum conditions were found to be 6.0 days, 6.5, 30 °C, 1.0 g/L, and 50 mg/L, respectively. The immobilized cell system exceeds the dye removal efficiency (RE) by 10. 7 % compared to the free cell system. The packed bed bioreactor could be able to deliver 98.56 % of dye removal at an inlet loading rate of 30 mg/L d and 50 mg/L of initial dye concentration.

Integration of orange peel derived carbon quantum dots with TiO2 for enhanced photocatalytic degradation of brilliant green dye

Brilliant green (BG) dye is a non-biodegradable, highly venomous and coloured pigment. BG dye possesses remarkably high visibility even at small concentration that causes diarrhea and abdominal pain in humans when being ingested. In addition, it is harmful to living organisms and polluting aquatic environments. Hence, eliminating BG dye from contaminated water is an urgent need. In this report, a photocatalyst encompasses hydrothermally prepared titanium dioxide (TiO2) integrated with orange peel derived oxygenated carbon quantum dots (O-CQDs) was developed for effective removal of BG dye. The O-CQDs were prepared using a single step eco-friendly hydrothermal process and an intense green fluorescence was observed upon exposing the O-CQDs to far UV light irradiation (254 nm). The formation of TiO2/O-CQDs nanohybrid was confirmed through UV–Visible spectrophotometer, X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) analyses. A random distribution of spherical shaped O-CQDs on the surface of TiO2 was clearly observed in FESEM images. The carboxyl groups present in O-CQDs not only increased interlayer spacing but also led to the attachment of TiO2 effectively. The TiO2/O-CQDs nanohybrid showed 94.70 % efficiency towards photocatalytic degradation of BG dye under UV light irradiation that was ∼20 % higher than the efficiency of pristine TiO2 photocatalyst. The presence of O-CQDs in the TiO2/O-CQDs nanohybrid boosted the photocatalytic degradation efficiency by enhancing UV light absorption and suppressing photo-generated electron–hole recombination. The integration of agricultural waste derived carbon with TiO2 by a facile synthesis method paves a way for large scale synthesis of TiO2/O-CQDs nanohybrid, which is anticipated to broaden its application potential in environmental remediation through photocatalytic degradation of organic compounds.

Bio-sourced multifunctional adsorbent of chitosan and adipic acid activated-dragon fruit peels for organic dye removal from water: Eco-friendly management and valorization of biomass

Employing sustainable biomaterials obtained from waste biomass and biopolymers provides a very promising method for eliminating organic dyes from wastewater. This study presents a novel adsorbent of modified dragon fruit peels and chitosan, addressing wastewater treatment and environmental waste management. Precisely, a bio-sourced multifunctional (high level of functional groups) adsorbent (hereinafter, CHS/DFP-ADP) was developed from chitosan and adipic acid activated-dragon fruit (Hylocereus polyrhizus) peels. This biomaterial was applied to effectively adsorb organic pollutants (safranin O dye, SAF-O) from water. The adsorption variables, namely A: CHS/DFP-ADP dosage (0.02–0.08 g), B: pH (4–10), and C: duration (10–40 min), were modeled and optimized using the Box-Behnken Design (BBD). The results of the BBD model showed the optimum adsorption parameters for achieving the highest level of SAF-O removal (94.83 %) were as follows: CHS/DFP-ADP does = 0.049 g, the pH ∼ 10, and the contact duration = 40 min. The experimental results on the dye adsorption by CHS/DFP-ADP demonstrated conformity with the pseudo-first-order and Freundlich models. The biomaterial demonstrated a significant capability to adsorb SAF-O dye, with an adsorption capacity of 607.2 mg/g. The adsorption process of the cationic dye on the CHS/DFP-ADP involves several interactions, such as Yoshida H-bonding, electrostatic forces, n-π, and H-bonding. This work aligns with the principles of green chemistry and sustainable development, offering an innovative approach to tackle environmental concerns and promote the circular economy. The present effort meets several Sustainable Development Goals (SDGs), such as SDG 6 (Clean Water and Sanitation), SDG 12 (Responsible Consumption and Production), SDG 13 (Climate Action), and SDG 14 (Life Below Water).

Process optimization of victoria blue dye removal using polypyrrole-encapsulated zirconium oxide: Mechanistic pathway and economic assessment

In this study, an organometallic composite, namely a polypyrrole-encapsulated zirconium oxide (ZrO2/PPy) nanocomposite, was developed and used to eliminate Victoria blue dye (VB) from water system. Specific surface area of the ZrO2/PPy obtained from BET study was observed to be 61.822 m2/g. Solution pH of 7.0, ZrO2/PPy nanocomposite dose of 0.8 g/L, sonication period of 40 min and initial VB dye concentration of 50 mg/L were chosen as optimal test parameters, at which 86.23 (±1.15) % of VB dye elimination was observed. The VB dye uptake process follows pseudo-second-order kinetic model and Langmuir isotherm model, with the later providing the maximum VB dye adsorption capacity of ZrO2/PPy nanocomposite as 238.09 mg/g. Thermodynamics study suggests the spontaneous (ΔGo< 0) and endothermic (ΔHo> 0) nature of the adsorption study. Food processing wastewater causes maximum hindrance (∼20 (±0.90) % −25 (±1.03) %) in the VB dye uptake process while the presence of phosphate (PO43−) ions can create highest interference (∼17 (±0.93) % −19 (±1.08) %) in the VB dye uptake process. At the optimum test parameter values (adsorbent dose: 1.3 g/L, initial VB dye concentration: 20 mg/L, sonication period: 70 min) as suggested by response surface methodology (RSM), maximum VB dye elimination of ∼96 % was observed. Electrostatic attraction, π–π interaction and hydrogen bond formation are amongst the major uptake mechanisms. Regeneration study indicates ∼19 (±1.36) % of decrease in VB dye elimination (%) after fifth cycle of reuse. The lab scale and industrial scale fabrication expense of 1.0 kg of ZrO2/PPy nanocomposite were obtained as 75.74 and 22.20 USD, respectively. The findings of this study suggest the potential of ZrO2/PPy nanocomposite as an effective and economically viable adsorbent to eliminate VB dye from wastewater.

Exploration of the role of Hibiscus esculentus (okra) mucilage for the removal of phenothiazinium dyes from water body: Spectroscopic, thermodynamic and molecular modeling study

Environmental pollution poses a major problem now a day. Several dyes, in the form of industrial waste, pollute water body and may cause adverse effects to human health. In this paper ADME and toxicity of fives Phenothiazinium group of dyes Methylene blue (MB), Azure A (AA), Azure B (AB), Azure C (AC) and Toluidine Blue O (TBO) were predicted using Swiss ADME and Protox II tools. Results showed these dyes may herm for living organism due to their carcinogenic, mutagenic and hepatotoxic properties. Removal efficiency of these dyes using okra plant product were determined using spectroscopic, thermodynamic and molecular modeling study. It was revealed that these dyes adsorb on the surface of okra leaf mostly at pH 7.0 and the adsorption isotherms were found to fit in Langmuir and Freundlich isotherm model, while Temkin model fails to do this. Mucilage present in different parts of okra plant plays a significant role on removal of these dyes and is able to remove near about 71–92 % of dyes from water body by itself. As this process did not fit in any of above said adsorption isotherm model, it may be suggested that some other mechanism may happen. Further studies explore that these dyes bound to the hydrophobic pocket of mucilage with binding affinity in the order of 105 M−1 and the bindings were exothermic in nature with enthalpy change in the range of − 2.94 to − 4.28 kcal/mole. Molecular docking study validate all the experimental results obtained from spectroscopic and thermodynamic study and enlighten the role of structure of dyes on their binding affinity to mucilage. This paper will help to systematically understand the role of okra plant products on removal efficiency of Phenothiazinium group of dyes with their structural variations.

Green Synthesis Study: Adsorption of Congo Red Dye with Selenium Nanoparticles Obtained from Prunus Armeniaca L. Leaf Waste

AbstractIn this study, it was aimed to remove Congo Red (CR) dye in aqueous solution by biosynthesized Selenium Nanoparticles from Prunus armeniaca L. (PAL‐SeNPs) leaf wastes by green synthesis method. The characteristic structure of PAL‐SeNPs was determined by UV‐vis spectroscopy, X‐ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscope (SEM), energy dispersive X‐ray (EDX), fourier transform infrared spectroscopy (FTIR), thermogravimetry‐differential thermal analysis (TGA‐DTA), dynamic light scattering (DLS), zetasizer, and point of zero charge (pHpzc). The effects of pH, adsorbent amount, time, initial concentration, and temperature were investigated by batch adsorption studies. 2 different kinetic and 4 isotherm models were tested and error analysis functions were determined for the most suitable model. Accordingly, the particle size, crystallinity, pHpzc value and average surface charge of PAL‐SeNPs were determined as 9.969 nm, 48.50 %, 3.47, and −23.6 mV, respectively. Also, the most suitable kinetic and isotherm models for the removal of CR dye with PAL‐SeNPs were found as Pseudo‐second‐order and Freundlich, with R2 values of 0.996, respectively. Also, where the optimum pH was 7.00, the maximum adsorption capacity was calculated as 96.59 mgCR/gPAL‐SeNPs. The results obtained show that environmentally friendly and low‐cost PAL‐SeNPs produced by the green synthesis method are a suitable alternative for the removal of CR dye.

Removal of Dyes from Waste Water Using Low‐Cost Adsorbents

AbstractThe principal objective of this article is a thorough analysis of the usage of inexpensive adsorbents to eliminate dyes from different aquatic environments. Dyes, commonly employed in industries—textiles, pharmaceuticals, and food, pose a significant environmental concern due to their persistence and potential toxicity. In response, researchers have explored the efficacy of low‐cost adsorbents (LCAs) as sustainable and economical alternatives for dye elimination. An overview of the environmental effects of dye contamination and the difficulties in using traditional dye removal techniques is given at the outset of the paper. It then delves into the diverse range of LCAs, including agricultural by‐products, waste materials, and natural substances, that have shown promise in adsorbing and eliminating dye contaminants. Examples of such adsorbents include activated carbon (AC) derived from agricultural residues, bio‐adsorbents from various plant materials, and industrial by‐products with inherent adsorption properties. Key mechanisms involved in the adsorption process, such as surface chemistry, pore structure, and electrostatic interactions, are elucidated to offer a fundamental understanding of the sorption capabilities of these materials. This comprehensive review consolidates the current knowledge on dye removal utilizing LCAs, offering insights into the challenges, advancements, and future directions in this environmentally significant field. The findings underscore the potential of harnessing readily available, sustainable materials as effective sorbents for mitigating the adverse impacts of dye pollutants in aqueous systems. The adsorption capacity is comparable to supplementary adsorbents suggested for the removal of dyes. The widely accessible adsorption properties of basic and acidic dyes do not significantly differ from one another.

Plasmon and N-vacancy synergistically enhanced tubular carbon nitride-based S-scheme heterojunction photocatalyst with one stone five birds function: Pathways, DFT calculation and mechanism insight

From the perspectives of innovation and broad-spectrum, tubular carbon nitride-based photocatalyst, viz., Ag/AgI/g-C3N4 S-scheme heterojunction photocatalyst, with enhancement of nitrogen vacancy and localized surface plasmon resonance (LSPR) effect is reasonably devised and manufactured via combining hydrothermal, calcination and photo-reduction techniques. The optimal specimen displays high photocatalytic activity in removal of dyes (such as crystalline violet, 100.00 %/60 min), antibiotics (such as levofloxacin, 88.72 %/50 min) and Cr6+ (100.00 %, 30 min), photocatalytic hydrogen evolution (1023.3 μmol h−1 g−1) and H2O2 generation (866.2 μmol h−1 g−1), achieving broad-spectrum natures, viz., realizing the function of “one stone five birds”. The broad-spectrum natures are attributed to the synergisms of nitrogen vacancy, LSPR effect of Ag, hollow tube structure and S-scheme heterojunction, which facilitate the separation and migration of photo-generated carriers and inject “hot electrons” generated by Ag into the conduction band of Ag/AgI/g-C3N4, increase the specific surface area and broaden the spectral response range. Further, the degraded intermediates of crystalline violet and levofloxacin and possible degradation pathways are rationally advanced by the aid of LCMS spectra, and synergistically enhanced photocatalytic mechanism of Ag/AgI/g-C3N4 hollow tube S-scheme heterojunction is confirmed based upon a series of sound experiments, fs-TA spectra, in-situ XPS and DFT calculation, etc.

Optimization study of methylene blue dye adsorption on Chamaerops humilis fibers biosorption using a central composite design

This research explores the effectiveness of Chamaerops humilis (CH) fibers as a biosorbent for the adsorption of Methylene Blue (MB) dye from aqueous solutions. The fibers were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR). To optimize the dye removal process, a Design of Experiments methodology, specifically Central Composite Design (CCD), was applied. Factors such as solution pH, adsorbent dosage, contact time, and temperature were varied. The CCD analysis identified the optimal conditions for maximum removal efficiency (99.87 %) of a 10 mg/L MB solution, which were: 1.06 g/L of CH fiber dosage, pH 9.6, and a contact time of 60 min. The adsorption process aligned well with a pseudo-second-order kinetic model, and the maximum adsorption capacity of CH fibers was determined to be 9.422 mg/g. Thermodynamic parameters, including Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) changes, were calculated, confirming that the adsorption is spontaneous and endothermic. The study highlights the potential of Chamaerops humilis fibers as an efficient and eco-friendly adsorbent for MB dye removal, offering a sustainable and cost-effective solution for wastewater treatment, particularly in industrial effluent management.

Synthesis of novel composite material with spent coffee ground biochar and steel slag zeolite for enhanced dye and phosphate removal.

Rising concerns over water scarcity, driven by industrialization and urbanization, necessitate the need for innovative solutions for wastewater treatment. This study focuses on developing an eco-friendly and cost-effective biochar-zeolite composite (BZC) adsorbent using waste materials-spent coffee ground biochar (CGB) and steel slag zeolite (SSZ). Initially, the biochar was prepared from spent coffee ground, and zeolite was prepared from steel slag; their co-pyrolysis resulted in novel adsorbent material. Later, the physicochemical characteristics of the BZC were examined, which showed irregular structure and well-defined pores. Dye removal studies were conducted, which indicate that BZC adsorption reach equilibrium in 2h, exhibiting 95% removal efficiency compared to biochar (43.33%) and zeolite (74.58%). Moreover, the removal efficiencies of the novel BZC composite toward dyes methyl orange (MO) and crystal violet (CV) were found to be 97% and 99.53%, respectively. The kinetic studies performed with the dyes and phosphate with an adsorbent dosage of 0.5g L-1 suggest a pseudo-second-order model. Additionally, the reusability study of BZC proves to be effective through multiple adsorption and regeneration cycles. Initially, the phosphate removal remains high but eventually decreases from 92% to 70% in the third regeneration cycle, highlighting the robustness of the BZC. In conclusion, this study introduces a promising, cost-effective novel BZC adsorbent derived from waste materials as a sustainable solution for wastewater treatment. Emphasizing efficiency, reusability, and potential contributions to environmentally conscious water treatment, the findings highlight the composite's significance in addressing key challenges for the removal of toxic pollutants from the aqueous solutions. PRACTITIONER POINTS: A novel biochar-zeolite composite (BZC) material has been synthesized. Excellent removal of dyes by BZC (~95%) was achieved as compared to their counterparts The kinetic studies performed suggest a pseudo-second-order model. BZC proves to be highly effective for multiple adsorption studies. Excellent reusability showed potential as a robust adsorbent.

Development of composite ultrafiltration membrane from fly ash microspheres and alumina nanofibers for efficient dye removal from aqueous solutions

In this work, a novel type of ultrafiltration ceramic membranes with the support based on fine fly ash microspheres and selective layer based on the alumina nanofibers with an aluminosilicate binder is proposed. The average pore sizes of the support and selective layer are 0.46 μm and 29 nm, respectively. The membrane is characterized by the compressive strength of 96 MPa and water permeability of 207 L m−2 h−1 bar−1. It is shown that the binder provides structural stability of selective layer and adhesion to the support. With increasing the binder content, the water permeability increases, reaches maximum, and then slightly decreases. The developed membranes are used for ultrafiltration of Blue Dextran dyes aqueous solutions with molecular weights of 70 kDa and 500 kDa and concentrations of 50 and 100 mg/L. The dyes rejection varies in the range 97–99 %, while the permeate flux is 100–140 L m−2 h−1 at the transmembrane pressure of 4 bars. The dye retention occurs via adsorption at the initial stage, which leads to the narrowing of pore size. Further, the dye filtration proceeds mainly due to size effects. The proposed membranes can be employed for dye removal from wastewater, and also allow chemical modification by carbon coating to be employed in electrochemically assisted ultrafiltration. The developed methodology promotes the recycling of thermal energy waste and introduces novel approaches to combine waste and synthesized raw materials in the production of low-cost ceramic membranes.

Synthesis and application of novel sodium carboxy methyl cellulose-g-poly acrylic acid carbon dots hydrogel nanocomposite (NaCMC-g-PAAc/ CDs) for adsorptive removal of malachite green dye

This study aimed on synthesizing novel sodium carboxy methyl cellulose-g-poly acrylic acid carbon dots hydrogel nanocomposite (NaCMC-g-PAAc/ CDs) to remove malachite green (MG) dye from aqueous media. The characterisation of functionalities, morphology, particle size and crystallography of NaCMC-g-PAAc/ CDs nanocomposite both before and after adsorption. The results of the characterization analysis revealed the presence of numerous ionic functionalities such as carboxyl, amino and hydroxyl groups in nanocomposite. The morphological study revealed the presence of porosity, heterogenous and amorphous nature of adsorbent favoring the adsorption of MG. Furthermore, elemental analysis also confirmed the presence of carbon and oxygen as main elemental composition of nanocomposite. The temperature of 30 °C and the nanocomposite (having pHPZC of 3) dose of 0.06g at pH 10 results in achieving 96.92% of MG dye removal. The experimental data fits closely with pseudo-second and Freundlich models. The enhanced MG dye adsorption by NaCMC-g-PAAc/ CDs was attributed to different mechanisms such as electrostatic or H-bonding as well as pi-pi interactions. Thermodynamically, the studied process was spontaneous and is of endothermic kind. Overall, the study reveals adsorptive property of novel NaCMC-g-PAAc/ CDs nanocomposite as a promising adsorbent for MG dye adsorption from water.

Transforming waste to purity: 3D electro-Fenton process boosted with pistachio shell-derived iron-biochar electrode for methyl violet 2B dye catalytic removal

Traditional degradation methods with typical catalysts which have limited negatively charged surfaces are not effectively degrade cationic dyes. A multi-functional iron-biochar was prepared from waste pistachio shells (Fe@PSB) that offers enhanced dye removal due to abundance of negatively charged sites for the degradation of the carcinogenic dye known as methyl violet 2B (MV 2B) in a cutting-edge three-dimensional electrochemical Fenton system (3DEF) with graphite (GP) cathode and Titanium (Ti) anode (3DEF-Ti/GP). Catalytic properties of Fe@PSB were explored for MV 2B dye degradation at broad acidic pH range. At optimum operating conditions of the current of 2.0A, pH 5.0, and Na2SO4 dose of 0.2M, nearly 98.8% of 10mg/L MV 2B dye removal was attained in 60min of electrolysis time. Commercial particle electrodes did not perform as well for the MV 2B dye degradation. The catalytic mechanism of 3DEF-Ti/GP system was investigated by quenching experiments which revealed that the hydroxyl radical (•OH) was responsible for the oxidation of dye molecules. Fe@PSB significantly performed up to four successful cycles. Liquid chromatography-mass spectrometry analysis revealed that de-methylation was the primary degradation pathway. This unique approach not only valorizes agricultural waste but also paving the way for greener environmental solutions.

Chitosan‐Carbon Aerogel for Efficient Removal of Methylene Blue Dye: Synthesis, Characterization, Adsorption Mechanism and Antimicrobial Therapies

AbstractChitosan‐carbon aerogel was synthesized via a facile and eco‐friendly method and characterized for its structural and morphological properties. The composite exhibits remarkable adsorption kinetics and a high potential for removing Methylene Blue (MB) dye, attributed to its enhanced surface area, porous structure, and active functional groups. The adsorption capacity of chitosan‐carbon aerogel increased from 38 to 86.8 mg/g as the pH was raised from 2 to 7. The maximum MB adsorption capacity increased from 22 to 632 mg/g as the initial MB concentration increased from 25 to 2000 mg/L. The saturation adsorption capacity of the chitosan‐carbon aerogel was 668 mg/g. After five reuse cycles, the removal efficiency dropped from 89 % to 73.1 %. Antibacterial tests showed that the width of the inhibition zone for S. enterica was 16.2 ± 0.38 mm, indicating similar antibacterial activity for both chitosan and chitosan‐carbon aerogels. These findings underscore the potential of chitosan‐carbon aerogel as a sustainable and cost‐effective solution for dye removal in wastewater treatment.

Enhanced photocatalytic removal of methyl orange dye employing SiO2/Mn2O3 based nanocatalyst under visible light

Surface water contamination by dye pollutants is a global environmental concern. The treatment of effluent from textile waste using metal oxide-based photocatalysts is a widely employed approach owing to its efficacy and simplicity. Herein, the synthesis and fabrication of novel visible radiation receptive manganese oxide and mesoporous silica nanocomposites (Mn2O3/SiO2) is described. Surface morphology of nanocomposites using scanning electron microscopy (SEM) displayed spherical shaped agglomerated structure. The chemical composition of nanocomposites was examined by using energy dispersive x-ray (EDX) analysis respectively indicating the presence of respective elements. Structural analysis was carried out by using XRD spectroscopy, while optical properties were evaluated by employing UV–visible spectroscopy. The photocatalytic activity of pure Mn2O3 and SiO2 nanoparticles as well as their nanocomposites with two different ratios Mn2O3/SiO2 (1:3) and Mn2O3/SiO2 (3:1) were evaluated by using methyl orange (MO) as a model dye. The band gap energy of Mn2O3/SiO2 (1:3) and Mn2O3/SiO2 (3:1) nanocomposite was 2.39 eV and 1.69 eV respectively. The nanocomposites exhibited improved photocatalytic efficiency as compared to pure nanoparticles as a function of pH and mixing ratio. For instance, at pH 7.0, Mn2O3/SiO2 (1:3) nanocomposite has depicted maximum degradation efficiency of 68 % for degradation of MO as compared to Mn3O4/SiO2 (3:1) nanocomposite, Mn3O4 and SiO2 nanoparticles. However, at pH 2.0 Mn2O3/SiO2 (3:1) nanocomposite had shown maximum degradation efficiency of 99 % as compared to Mn2O3/SiO2 (1:3), Mn2O3 and SiO2 nanoparticles. The degradation reaction followed pseudo first order kinetics. At pH 7.0, the rate constant values of nanocomposites i.e. Mn2O3/SiO2(1:3) and Mn2O3/SiO2(3:1) comes out to be 4.68 × 10−3 min−1 and 2.49 × 10−3 min−1 respectively. At pH 2.0, the rate constant values calculated for Mn2O3/SiO2(1:3) nanocomposite and Mn2O3/SiO2(3:1) nanocomposite was 4.91 × 10−3 min−1 and 1.24 × 10−2 min−1 respectively. The easy fabrication of these nanocomposites coupled with facile tuning of their properties make them suitable contenders for efficient dye degradation in wastewater treatment.

Cationic dye remediation in water treatment with Lizardite–Rice Husk composite: A statistical physics approach

This study presents the development of a novel composite adsorbent, Lizardite-Rice Husk Composite (LRHC), synthesized from lizardite, a mineral derived from chromite ore waste, and rice husk, an agricultural byproduct. The primary objective was to evaluate the efficiency of LRHC in the adsorption of cationic dyes, Malachite Green (MG) and Methylene Blue (MB), from aqueous solutions. Systematic investigations were conducted to assess the influence of adsorbent mass, initial dye concentration, stirring speed, and contact time on adsorption performance. The results revealed that LRHC exhibited optimal adsorption capacities at pH values above 5, with MB and MG adsorption capacities reaching 309.75 mg/g and 51.43 mg/g, respectively. Adsorption equilibrium for MB was achieved within 30 min, indicating rapid dye uptake. Isotherm analysis demonstrated that the Temkin model best described MB adsorption, while the Freundlich model was more suitable for MG, with favorable Langmuir constants. Kinetic studies confirmed that the adsorption followed a second-order model, suggesting chemisorption as the rate-determining step. Intraparticle diffusion and mass transfer were identified as significant contributors to the adsorption process. Thermodynamic studies indicated that MB adsorption was spontaneous (ΔG° = −4.69 kJ/mol for the concentration of 50 mg/L at 298 K) and that MG adsorption was non-spontaneous (ΔG° = 1.52 kJ/mol for the concentration of 50 mg/L at 298 K), with spontaneity increasing at higher initial concentrations. Statistical physics modeling, particularly the monolayer model, provided detailed insights into the adsorption mechanisms and geometry. Furthermore, LRHC demonstrated excellent reusability, maintaining over 80% of its initial adsorption capacity after four regeneration cycles via a heterogeneous Fenton-like reaction. The combination of easy availability, cost-effectiveness, and environmental friendliness makes LRHC a superior adsorbent for the removal of cationic dyes compared to conventional alternatives. This research contributes novel insights into the design and application of composite adsorbents, offering a sustainable solution for water treatment and addressing significant environmental challenges.

Adsorption Behavior of Methylene Blue Onto Activated Coconut Shells: Kinetic, Thermodynamic, Mechanism and Regeneration of the Adsorbent.

Adsorption techniques are widely used to remove some classes of pollutants from waters, especially those which are not easily biodegradable. The removal of Methylene blue (MB), as a pollutant, from waste waters of textile, paper, printing and other industries has been addressed by the researchers. The aim of this study is to eliminate MB by Activated Coconut Shells (ACS) produced at low cost by adsorption in batch mode. The ACS was characterized by the FTIR spectroscopy and point of zero charge (pHpzc: 5.06). Some examined factors were found to have significant impacts on the MB uptake of ACS like the initial dye concentration Co (40-120mg/L), solution pH (2-8), ACS dose (1-12g/L), agitation speed (50-500 r/min), particles size (1.0-1.2mm) and temperature (298-333K). The best capacity was found at pH 6 with an adsorbent dose 8g/L, an agitation speed 200 r/min and a contact time of 60 min. Modeling Kinetics and Isotherms shows that the pseudo-second-order kinetic model with R 2 (0.935 -0.998) and Langmuir adsorption isotherm model provide better fitness to the experimental data with the maximum adsorption capacity of 30.30mg/g at 25°C. The separation factor RL (0.933-0.541) in the concentration range studied (10-120mg/L) shows a favorable adsorption. The isotherms at different temperatures have been used for the determination of the free energy ΔG° (198-9.72kJ/mol); enthalpy ΔH° (82.082kJ/mol) and entropy ΔSo (245.689J/K mol) to predict the nature of MB adsorption process. The positive values of (ΔGo) and (ΔHo) indicate a non-spontaneous and endothermic MB adsorption with a chemisorption. The adsorbent elaborated from Coconut Shells was found to efficient and suitable for the removal of MB dye from aqueous solutions, due to its availability, low cost preparation and good uptake capacity.

Purification of textile wastewater by collective degradation using nanorods of cesium titanium bromide (CsTiBr3) perovskite

The present work recommends a sustainable environmentally safe method for the removal of textile dyes in an economically viable way.The wastewater expelled from the textile dying units contains a mixture of dyes. Here we address the challenge of using a single catalyst for the collective photocatalytic degradation of mixture of six dyes and two samples of textile effluents collected from a local dying unit under direct sunlight. The lead-free perovskite of CsTiBr3 nanorods prepared via the solvothermal process is effective in the collective photocatalytic degradation of dye mixture containing toxic dyes like congo red, crystal violet, malachite green, methylene blue, rhodamine, and methyl orange. The six-dye mixture turned colorless within three hours of direct sunlight exposure. The collective photocatalytic degradation ability of CsTiBr3 perovskite nanorods is successfully exploited for the degradation of the textile effluents. The chemical oxygen demand (COD) analysis guarantees the degradation of dye into non-toxic components. The recycling of wastewater is made possible by the removal of CsTiBr3 catalysts through adsorption using biochar derived from invasive plants. The biochars are extracted from invasive plants such as Acrostichum Aureum, Alternanthera bettzickiana, cyclosorus interrupts, and Quisqualis indica in which Acrostichum Aureum showed maximum adsorption. The scavenger studies using isopropyl alcohol (IPA), ethylene diamine tetra acetic acid (EDTA), and silver nitrate (AgNO3) suggest that holes control the photocatalysis mechanism.

Hydrothermally synthesized Sr-doped In2S3 microspheres for efficient degradation of noxious RhB pollutants in visible light exposure

A series of SrxIn2-xS3 (x = 0, 2, 4, 6 and 8 mol%) microspheres have been prepared at 160°C using hydrothermal approach and examined the impact of Sr doping on its structural, morphological, optical and photocatalytic properties. Structural properties have been investigated using X-ray diffraction (XRD) with Rietveld refinement. Morphology and elemental composition have been analysed using Field emission scanning electron microscopy (FESEM) and Energy dispersive X-ray Spectroscopy (EDX), respectively. Optical band gap energy (Eg) has been determined using Diffuse reflectance Spectroscopy (DRS) and found to range between 2.15 eV to 2.07 eV. Photoluminescence (PL) emission spectra confirm a decrease in charge carrier recombination rate with Sr doping. The negative surface potential has been assessed by the Zeta analyzer, which indicates its suitability for the degradation of cationic dyes such as Rhodamine-B (RhB). Among the SrxIn2-xS3 microspheres, Sr0.04In1.96S3 demonstrated highest photocatalytic efficiency ∼98 % degradation of RhB pollutant (10 ppm) in 240 min. using 10 mg of catalyst per 100 ml. The adsorption kinetics in the presently studied samples obeys the pseudo 2nd order kinetic model. This study highlights the significant impact of Sr doping on the photocatalytic efficiency of SrxIn2-xS3 microspheres, offering promising applications in removal of RhB dye.