Enhanced photocatalytic removal of Safranin-T dye under sunlight within minute time intervals using heulandite/polyaniline@ nickel oxide composite as a novel photocatalyst

Tailored bimetallic Zn/Ni and Zn/Ag MCM-41 photocatalysts for enhanced visible-light photocatalytic tetracycline degradation

Novel bimetallic-doped-MCM-41(Mobil Composition of Matter No. 41) (Zn/Ni-MCM-41 (ZNM)) and (Zn/Ag-MCM-41 (ZAM)) catalysts were synthesized and characterized for their structural, textural, morphological, and optical properties. XRD analysis confirmed metal incorporation into the MCM-41 framework, while N2 adsorption-desorption isotherms indicated a decrease in specific surface area (1210 in pure MCM-41 to 722.86 and 700.36 m2/g for ZNM and ZAM, respectively) due to partial pore filling. TEM images verified this finding. Boosted absorption extending into the visible light region was detected in the metal incorporated (ZNM and ZAM) samples with additional band gaps, related to transitions in Zn2+, Ag+ and Ni2+ ions. Photoluminescence studies revealed efficient charge carrier separation in ZNM and ZAM. Both catalysts exhibited superior tetracycline (TC) removal from aqueous solution with efficiency (95.59% and 95.30% within one hour for ZNM and ZAM, respectively) with pronouncing visible light photocatalytic capability compared to pure MCM-41. The degradation process followed pseudo-first-order kinetics. The enhanced photocatalytic activity of ZNM and ZAM is attributed to the synergistic effects of metal incorporation, increased light absorption, and efficient charge carrier dynamics. Additionally, a possible photocatalytic mechanism for degradation of TC over ZNM and ZAM has been proposed and involvement of superoxide radicals (O2•-) and holes (h+) as reactive species is elucidated by radical trapping experiments. A distinct pH-dependent trend was observed in TC degradation efficiency using the ZAM photocatalyst. The efficiency gradually increased with increasing pH until reaching a maximum at pH 7, followed by a decline at higher pH values. These results demonstrate the potential of ZNM and ZAM as promising materials for removal of tetracycline antibiotic from water.

Exploring zeolite-based composites in adsorption and photocatalysis for toxic wastewater treatment: Preparation, mechanisms, and future perspectives

Water scarcity has become a critical global concern exacerbated by population growth, globalization, and industrial expansion, resulting in the production of wastewater containing a wide array of contaminants. Tackling this challenge necessitates the adoption of innovative materials and technologies for effective wastewater treatment. This review article provides a comprehensive exploration of the preparation, applications, mechanisms, and economic environmental analysis of zeolite-based composites in wastewater treatment. Zeolite, renowned for its versatility and porous nature, is of paramount importance due to its exceptional properties, including high surface area, ion exchange capability, and adsorption capacity. Various synthetic methods for zeolite-based composites are discussed. The utilization of zeolites in wastewater treatment, particularly in adsorption and photocatalysis, is thoroughly investigated. The significance of zeolite in adsorption and its role in the photocatalytic degradation of pollutants are examined, along with its applications in treating volatile organic compounds (VOCs), dye wastewater, oil-field wastewater, and radioactive waste. Mechanisms underlying zeolite-based adsorption and photocatalysis, including physical and chemical adsorption, ion exchange, and surface modification, are elucidated. Additionally, the role of micropores in the adsorption process is explored. Furthermore, the review delves into regeneration and desorption studies of zeolite-based composites, crucial for sustainable wastewater treatment practices. Economic and environmental analyses are conducted to assess the feasibility and sustainability of employing zeolite-based composites in wastewater treatment applications. Future recommendations are provided to guide further research and development in the field of zeolite-based composites, aiming to enhance wastewater treatment efficiency and environmental sustainability. By exploring the latest advancements and insights into zeolite-based nanocomposites, this paper aims to contribute to the development of more efficient and sustainable wastewater treatment strategies. The integration of zeolite-based materials in wastewater treatment processes shows promise for mitigating water pollution and addressing water scarcity challenges, ultimately contributing to environmental preservation and public health protection.

Zeolite 13X incorporated with Zn-Ce oxide nanocatalyst for removal of Reactive Red 120 dye: RSM-based approach

In this study, the photocatalytic removal of Reactive Red 120 (RR120) dye was examined using zeolite 13X incorporated with Zn-Ce under UV irradiation. The synthesis of Zn-Ce nanoparticles incorporated with zeolite 13X was conducted through the co-precipitation method, and the features of the prepared nanocatalyst were analyzed using various techniques. The SEM and BET analyses indicated successful incorporation of ZnO-Ce oxides on the surface of zeolite 13X and a specific surface area of 359.39 m2/gm, respectively. Further, the average size of crystal grains was 28 nm. The response surface methodology (RSM) approach was employed to optimize operating parameters. The quadratic model suggested by the RSM approach, characterized by a high regression coefficient (R2 = 0.9632), indicates a high level of reliability. Moreover, under optimal conditions (catalyst loading of 4 mg, pH of 3, H2O2 amount of 0.2 mL, UV power of 25 W, and reaction time of 60 min), the highest RR120 dye removal percentage was 99.97%. Kinetic data indicated an increase in the reaction rate constant from 0.0631 to 0.1796 min-1. The zeolite 13X incorporated with Zn-Ce photocatalyst exhibited excellent stability over 5 cycles, with only a 5.50% decrease in RR120 dye removal yield. This study demonstrates the promising potential of zeolite 13X incorporated with Zn-Ce nanoparticles for the removal of RR120 dye from aqueous suspension.

Nickel-Based Bifunctional Cocatalyst to Enhance CdS Photocatalytic Hydrogen Production

The design of nanocomposites as a light-capturing system applied in photocatalytic water splitting is an emerging area of research. In our study, a simple in situ photodeposition method was proposed for the synthesis of CdS nanoflowers modified by nickel-based bifunctional, i.e., Ni/Ni(OH)2, cocatalysts. The introduction of cocatalysts has demonstrated a notable enhancement in the photocatalytic hydrogen evolution efficiency of CdS. The quantity of cocatalysts supported on CdS played an important role in governing the light absorption capability and photocatalytic efficacy. Ni-CdS-10 showed the best photocatalytic activity of 30.51 mmol g-1 h-1, which was 1.8 times and 2.6 times higher activity than Pt-CdS-1 wt % and pure CdS, respectively. Mechanism studies with UV-vis DRS, photoluminescence, and Mott-Schottky plots revealed the intrinsic electric field created at the p-n Ni(OH)2/CdS junctions, which can effectively implement the transport and separation of photoinduced carriers. From linear sweep voltammetry, electrochemical impedance spectroscopy, and DFT calculation, both Ni(OH)2 and Ni can effectively decrease the Gibbs free energies of hydrogen adsorption and reduce the overpotential of hydrogen evolution. As a result, the efficiency of generating H2 through photocatalysis experienced significant improvement, and the participation of bifunctional cocatalysts further reduced the photocorrosion of CdS, enhanced stability, improved low price, and efficient photocatalyst production.

Enhanced Photocatalytic Degradation of Malachite Green Dye Using Silver-Manganese Oxide Nanoparticles

Efficient and excellent nanoparticles are required for the degradation of organic dyes in photocatalysis. In this study, silver-manganese oxide nanoparticles (Ag-Mn-NPs) were synthesized through a wet chemical precipitation method and characterized as an advanced catalyst that has enhanced photocatalytic activity under sunlight irradiation. The nanoparticles were characterized using scanning electron microscopy (SEM), XRD, UV-vis light spectra, and energy-dispersive X-ray (EDX) spectroscopy, revealing their spherical and agglomerated form. The EDX spectra confirmed the composition of the nanoparticles, indicating their presence in oxide form. These bimetallic oxide nanoparticles were employed as photocatalysts for the degradation of malachite green (MG) dye under sunlight irradiation in an aqueous medium. The study investigated the effects of various parameters, such as irradiation time, catalyst dosage, recovered catalyst dosage, dye concentration, and pH, on the dye's photodegradation. The results showed that Ag-Mn oxide nanoparticles exhibited high photocatalytic activity, degrading 92% of the dye in 100 min. A longer irradiation time led to increased dye degradation. Moreover, a higher catalyst dosage resulted in a higher dye degradation percentage, with 91% degradation achieved using 0.0017 g of the photocatalyst in 60 min. Increasing the pH of the medium also enhanced the dye degradation, with 99% degradation achieved at pH 10 in 60 min. However, the photodegradation rate decreased with increasing dye concentration. The Ag-Mn oxide nanoparticles demonstrate excellent potential as a reliable visible-light-responsive photocatalyst for the efficient degradation of organic pollutants in wastewater treatment.

Synthesis and characterization of NiO/Cr2O3 nanocomposite with effective sunlight driven photocatalytic degradation of organic dyes

In this paper, nanocomposite NiO/Cr₂O₃ has been synthesized by a simple chemical reduction method to study its photocatalytic activity under sunlight irradiation. Various advanced analytical techniques including powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), elemental mapping, Fourier transform infrared spectroscopy (FTIR), and UV-visible spectroscopy have been utilized to characterize the synthesized NiO/Cr₂O₃ nanocomposite. SEM images show the sheet-shaped morphology of NiO/Cr₂O₃ nanocomposite. These sheets have a rough surface with nano to micro size cracks. These cracks play important role in the enhancement of photocatalytic activity by increasing surface active sites for the adsorption of dye molecules on the surface of the photocatalyst. The organic dyes crystal violet (CV) and methylene blue (MB) have been chosen to study the photocatalytic behavior of NiO/Cr₂O₃ nanocomposite under sunlight irradiation. The photocatalytic efficiency of NiO/Cr₂O₃ nanocomposite has been obtained 88.47% and 93.63% against crystal violet and methylene blue respectively. The results of the photocatalytic kinetics exhibit that degradation rate constant value for crystal violet dye is higher as compared to methylene blue dye. Obtained kinetic results indicate that synthesized nanocomposite acts as an efficient photocatalyst for the degradation of both crystal violet dye and methylene blue dye. NiO/Cr₂O₃ nanocomposite also exhibited reusability and stability for photocatalytic degradation of both organic dyes. Photoelectrochemical measurements as photocurrent, electrochemical impedance spectroscopy (EIS), and Mott-Schottky plot were also performed for synthesized NiO/Cr₂O₃ nanocomposite. Consequently, this synthesized NiO/Cr₂O₃ nanocomposite can be utilized for environmental remediation of harmful dyes.

Superior removal of methylene blue using green fabricated pomegranate peel/nano-hematite composite: reusability, isotherm and kinetics study

Green hematite nanoparticles were synthesized using pomegranate peel extract of different concentrations (2 g, 4 g, and 6 g) and in the presence of the peel residuals. The obtained products defined as PP/GNH (I), PP/GNH (II), and PP/GNH (III) referring to the hematite nanoparticles at different concentrations compositing with pomegranate peel residuals. The products were addressed as green adsorbents for methylene blue dye contaminants in water. They exhibit superior adsorption properties with theoretical q_max of 666, 1111, and 909 mg/g for PP/GNH (I), PP/GNH (II), and PP/GNH (III), respectively. The equilibration times were attained after 480 min for the three products. The isotherm and kinetic studies indicate that the adsorption systems for the synthetic materials are of chemisorption type. The adsorption behaviors of these systems can be demonstrated according to Pseudo-second order as well as Elovich kinetic model. Furthermore, the adsorption results reflected a mono-layer uptake form which was more suitable for the Langmuir model than other investigated models. The products also showed high performances when it comes to remove the dyes investigated such as methylene blue Congo red, safranin, methyl orange, and crystal violet. Finally, green fabricated nano hematite/pomegranate peel composites are of high stability and can be reused for five cycles.Communicated by Ramaswamy H. Sarma.

Comprehensive Review on Zeolite-Based Nanocomposites for Treatment of Effluents from Wastewater

All humans and animals need access to clean water in their daily lives. Unfortunately, we are facing water scarcity in several places around the world, and, intentionally or unintentionally, we are contaminating the water in a number of ways. The rise in population, globalization, and industrialization has simultaneously given rise to the generation of wastewater. The pollutants in wastewater, such as organic contaminants, heavy metals, agrochemicals, radioactive pollutants, etc., can cause various ailments as well as environmental damage. In addition to the existing pollutants, a number of new pollutants are now being produced by developing industries. To address this issue, we require some emerging tools and materials to remove effluents from wastewater. Zeolites are the porous aluminosilicates that have been used for the effective pollutant removal for a long time owing to their extraordinary adsorption and ion-exchange properties, which make them available for the removal of a variety of contaminants. However, zeolite alone shows much less photocatalytic efficiency, therefore, different photoactive materials are being doped with zeolites to enhance their photocatalytic efficiency. The fabrication of zeolite-based composites is emerging due to their powerful results as adsorbents, ion-exchangers, and additional benefits as good photocatalysts. This review highlights the types, synthesis and removal mechanisms of zeolite-based materials for wastewater treatment with the basic knowledge about zeolites and wastewater along with the research gaps, which gives a quality background of worldwide research on this topic for future developments.

Design and Characterization of Zeolite/Serpentine Nanocomposite Photocatalyst for Solar Hydrogen Generation

In this work, a low-cost, high-yield hydrothermal treatment was used to produce nanozeolite (Zeo), nanoserpentine (Serp), and Zeo/Serp nanocomposites with weight ratios of 1:1 and 2:1. At 250 °C for six hours, the hydrothermal treatment was conducted. Various methods are used to explore the morphologies, structures, compositions, and optical characteristics of the generated nanostructures. The morphological study revealed structures made of nanofibers, nanorods, and hybrid nanofibril/nanorods. The structural study showed clinoptilolite monoclinic zeolite and antigorite monoclinic serpentine with traces of talcum mineral and carbonates. As a novel photoelectrochemical catalyst, the performance of the Zeo/Serp (2:1) composite was evaluated for solar hydrogen generation from water splitting relative to its constituents. At -1 V, the Zeo/Serp (2:1) composite produced a maximum current density of 8.44 mA/g versus 7.01, 6.74, and 6.6 mA/g for hydrothermally treated Zeo/Serp (1:1), Zeo, and Serp, respectively. The Zeo/Serp (2:1) photocatalysts had a solar-to-hydrogen conversion efficiency (STH) of 6.5% and an estimated hydrogen output rate of 14.43 mmole/h.g. Consequently, the current research paved the way for low-cost photoelectrochemical catalytic material for efficient solar hydrogen production by water splitting.

UV activated sodium percarbonate to accelerate degradation of atrazine: Mechanism, intermediates, and evaluation on residual toxicity by metabolomics

Efficient and safe removal of widely used herbicides such as atrazine has become a recent hotspot. Herein, UV driven sodium percarbonate system (UV/SPC) was established to have many advantages in remediation of atrazine contamination. The mechanism and environmental risk of intermediates were explored, which provided information for the feasibility of UV/SPC. The degradation efficiency of atrazine was significantly enhanced as the increasing dosage of SPC. Quenching assay identified that •OH and CO3•- were committed to degrading atrazine. Humic acid and HPO42- remarkably inhibited atrazine degradation. Several intermediates were generated through the dealkylation, dechlorination-hydroxylation, alkylic-hydroxylation, alkyl oxidation and olefination reactions. Toxicity prediction proved that acute toxicity and bioaccumulation of intermediates were mitigated comparing with atrazine. Based on metabolomics results, the alteration of key metabolites such as citrate, L-kynurenine, malic acid, putrescine, glutamine, spermine, ethanolamine and phytosphingosine in various metabolic pathways of E.coli verified that the toxicity of atrazine was weakened after UV/SPC treatment. The application of UV/SPC on atrazine removal in real waters was influenced by environmental factors, and might be improved through coupling with other treatment technologies.

Post-fabrication structural changes and enhanced photodegradation activity of semiconductors@zeolite composites towards noxious contaminants

This review article provides the recent progress in semiconductor-based zeolite photoactive materials for the application of noxious contaminants removal. The rapidly expanding industrialization and globalization cause serious threats to the environment or water bodies. The semiconductor@zeolite photocatalysts were implemented for water quality management/sustainment. The exclusive properties of zeolite material have been elaborated with their role in the photocatalysis process. The photoactive material's properties like single-atom catalysts (SACs), distribution of metal in the zeolite crystal were elaborated along with their role in catalytic reactions. Differently prepared semiconductor@zeolite composites such as TiO₂@zeolite, binary and ternary composites, Fe/Ag/bismuth-modified/ZnO/ZnS/NiO/g-C₃N₄/core-shell/quantum dots modified zeolite composites, were systematically summarized. The research progress in morphologies, structural effect, degradation mechanism were recapitulated and tabulated form of % degradation with their optimal parameters such as catalyst dose, pollutant concentrations, pH, light source intensities were also provided. The significance of zeolite frameworks, the structural properties of semiconductor@zeolite photoactive materials to enhance the degradation efficiencies was explored. Analysis of the intermediate products of Norfloxacin, TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin), TCDF (2,3,7,8-tetrachlorodibenzofuran), diclofenac contaminants were systematically represented and structurally identified by GC-MS/HPLC-MS techniques.

Highly Efficient Photocatalyst Fabricated from the Chemical Recycling of Iron Waste and Natural Zeolite for Super Dye Degradation

In this paper, Fe2O3 and Fe2O3-zeolite nanopowders are prepared by chemical precipitation utilizing the rusted iron waste and natural zeolite. In addition to the nanomorphologies; the chemical composition, structural parameters, and optical properties are examined using many techniques. The Fe2O3-zeolite photocatalyst showed smaller sizes and higher light absorption in visible light than Fe2O3. Both Fe2O3 and Fe2O3-zeolite are used as photocatalysts for methylene blue (MB) photodegradation under solar light. The effects of the contact time, starting MB concentration, Fe2O3-zeolite dose, and pH value on photocatalytic performance are investigated. The full photocatalytic degradation of MB dye (10 mg/L) is achieved using 75 mg of Fe2O3-zeolite under visible light after 30 s, which, to the best of our knowledge, is the highest performance yet for Fe2O3-based photocatalysts. This photocatalyst has also shown remarkable stability and recyclability. The kinetics and mechanisms of the photocatalytic process are studied. Therefore, the current work can be applied industrially as a cost-effective method for eliminating the harmful MB dye from wastewater and recycling the rusted iron wires.

Recent progress in g-C3N4, TiO2 and ZnO based photocatalysts for dye degradation: Strategies to improve photocatalytic activity

Water contamination by dyes is a matter of concern for human health and the environment. Various methods (membrane separation, coagulation and adsorption) have been explored to remove/degrade dyes. However, now the exploitation of semiconductor assisted materials using renewable solar energy has emerged as a potential candidate to resolve the issue. Although, single component photocatalysts (ZnO, TiO₂, ZrO₂) were experimented, due to their low efficiency and stability due to the high recombination rate electron-hole pair and inefficient visible light absorption, composites of semiconductor materials are being used. Semiconductor heterojunction systems are developed by coupling two or more semiconductor components. The synergistic effect of their properties, such as adsorption and improved charge carrier migration, is observed to increase overall stability. This review covers recent progress in advanced nanocomposite materials based on g-C₃N₄, TiO₂ and ZnO used as photocatalysts with details of enhancing the photocatalytic properties by heterojunctions, crystallinity and doping. The conclusion at the end displays a summary, research gaps and future outlook. A holistic analysis of recent progress to demonstrate the efficient heterojunctions for photodegradation with optimal conditions, this review will be helpful for the development of efficient heterostructured systems for photodegradation. This review covers references from the year 2017-2020.

Facile fabrication and application of poly(ortho-phenetidine) nanocomposite coating for solid-phase microextraction of carcinogenic polycyclic aromatic hydrocarbons from wastewaters

The waters and wastewaters around industrial areas are heavily polluted and have adverse effects on the ecosystems. The present study is mainly focused on the electropolymerization of ortho-phenetidine and co-deposited on a steel wire along with graphene oxide nanosheets as a novel coating for solid-phase microextraction of polycyclic aromatic hydrocarbons (PAHs) from aqueous media prior to gas chromatography-mass spectrometry. PAHs are composed of multiple aromatic rings which have been linked to skin, lung, bladder and liver. Cancer is a primary human health risk of exposure to PAHs. To obtain a firm and stable coating, several empirical factors relevant to the electrochemical process were investigated. Characterization for chemical structure and surface morphology of the synthesized nanocomposite was conducted with FT-IR spectroscopy and FE-SEM, respectively. XRD and TGA were applied to study the other properties of the nanocomposite. Some essential items involved in microextraction process were also checked in details. Under optimized case, validation parameters were assessed. Wide linearity (0.005-5.0 ng mL^-1), low detection limits (0.4-4.3 pg mL^-1) and good repeatability (3.6-9.5%) and reproducibility (7.6-11.8%) were achieved. The developed method was utilized to analyze contaminated real samples such as wastewater samples from coal processing industries and agricultural water samples collected from the vicinity of the industry in different seasons and high recoveries were obtained, finally.

Enhanced decontamination of levofloxacin as toxic pharmaceutical residuals from water using CaO/MgO nanorods as a promising adsorbent

Novel MgO/CaO nanocomposite (MgO/CaO NRs) was synthesized by the hydrothermal method using diatomite porous frustules as a substrate under the microwave irradiation. The composite appeared as well crystalline rod-like nanoparticles with 52.3 nm as average particle size and 112.8 m²/g as BET surface area. The synthetic MgO/CaO NRs were addressed as a novel adsorbent for promising removal of levofloxacin (LVX) as pharmaceutical residuals. The adsorption studies revealed effective uptake of levofloxacin by MgO/CaO NRs with theoretical q_max of 106.7 mg/g and the equilibrium time of 720 min considering the best pH value (pH 7). The equilibrium studies highly fitted with the Langmuir model of monolayer adsorption considering the values of Chi-squared (χ²) and determination coefficient. The estimated adsorption energy from Dubinin–Radushkevich (0.2 kJ/mol) signifies physisorption mechanisms that might be coulombic attractive forces considering the kinetic studies. The thermodynamic addressing for the reactions verified their spontaneous and exothermic nature within a temperature range from 303 to 333 K. Additionally, the prepared MgO/CaO NRs show significant recyclability properties to be used in realistic remediation process and its uptake capacity is higher than several studied adsorbents in literature.

Enhanced photocatalytic degradation of acephate pesticide over MCM-41/Co3O4 nanocomposite synthesized from rice husk silica gel and Peach leaves

Novel green nanocomposite from mesoporous MCM-41 and Co₃O₄ was synthesized from rice husk based silica gel and using the green extract of Peach leaves as reducing reagent. The composite was labeled as RH-MCM-41/Co₃O₄ and characterized by different techniques as green photocatalyst in the degradation of Acephate pesticide under visible light illumination. The composite showed well developed spherical MCM-41 particles decorated by nano Co₃O₄ nanoparticles with stunning surface area and low bandgap energy (1.51 eV). The composite displayed superior photocatalytic activities in the oxidation of Acephate which reflected in a complete degradation of different concentrations of it after 40 min (50 mg/L), 60 min (100 mg/L), 100 min (150 mg/L) and 140 min (200 mg/L) using 0.25 g of the composite. The complete removal of the present TOC for treatment of 100 mg/L acephate was achieved using 0.25 g after 70 min reflecting the formation of intermediate compounds during the oxidation steps. The reported intermediate compounds are CH₃C(O)NH₂, CH₃O(CH₃S)P(O)NH₂, (CH₃O)₂P(O)SCH₃, CH₃OP(O)(OH)₂, CH₃SS(O)₂CH₃, and (COOH)₂. All the formed intermediate compounds were degraded under the visible light photocatalytic activity of RH-MCM-41/Co₃O₄ into NO₃^-, SO₄^2-, PO₄^3-, and CO₂ as final products.

Removal of atrazine by biochar-supported zero-valent iron catalyzed persulfate oxidation: Reactivity, radical production and transformation pathway

Atrazine is a widely used herbicide whose presence poses a potential threat to agriculture and human living environment. This work studied the degradation performances and mechanisms of zero-valent iron and biochar composite (ZVI/BC) activated persulfate (PS) for atrazine. The results showed that the removal percentage of atrazine reached 73.47% within 30 min. Furthermore, the optimal parameters (175 mg/L ZVI/BC, 2 mM PS and initial pH of 3) were obtained through response surface methodology. Meanwhile, the high atrazine removal percentage (83.77%) was obtained under the optimal conditions. Radical quenching studies and electron spin resonance revealed that active substances produced during PS activation, as well as that SO₄·^- and HO· were dominant active species for the atrazine degradation. According to iron corrosion products and XPS analysis, the reaction mechanism of ZVI/BC-PS system was proposed as that ZVI loaded on the composites further activated PS to produce SO₄·^- and HO· which accompany with the valent changing of iron and finally causing degradation of atrazine. In addition, the degradation pathways of atrazine in ZVI/BC-PS system included dealkylation, alkyl oxidation and dechlorination-hydroxylation by the results of GC-MS and LC-MS. These findings demonstrated that ZVI/BC activated persulfate may be an efficient technique for the degradation of atrazine.

Effective oxidation of methyl parathion pesticide in water over recycled glass based-MCM-41 decorated by green Co3O4 nanoparticles

Pieces of glass as solid wastes were recycled in the synthesis of highly order MCM-41 that decorated by green fabricated Co₃O₄ nanoparticles using the green extract of green tea leaves forming novel green nano-composite. The synthetic Co₃O₄/MCM-41 exhibit high surface area, low bandgap energy (1.63 eV), and typical spherical morphology decorated by Co₃O₄ nanoparticles. The composite was evaluated as green photocatalyst in effective oxidation of methyl parathion pesticide in the presence of a visible light source. The degradation results revealed complete removal of 50 mg/L and 100 mg/L after 60 min and 90 min, respectively using 0.25 of the catalyst at pH 8. The detection of the TOC in the treated methyl parathion solution gives strong indications about the formation of organic intermediate compounds during the oxidation steps. The main detected intermediate compound are C₆H₅OH(NO₂), C₆H₅OH, (CH₃O)₃P(S), C₆H₄(OH)₂, C₆H₃(OH)₃, C₆H₄(NH₂)OP(O)(OCH₃)₂, (CH₃O)₂P(O)OH, (CH₂)₂C(OH)OH(CHO)OC(O), and HO₂C(CH₂)₂C(O)CHO. The detected intermediate compounds converted into SO₄^2-, PO₄^3-, NO₃^-, and CO₂ under the extensive photocatalytic of them over Co₃O₄/MCM-41. The oxidizing species trapping test verified the controlling of the methyl parathion degradation pathway by the hydroxyl radicals. Finally, the composite showed significant reusability properties and applied five times in the oxidation of methyl parathion with considerable degradation percentages.

Photocatalytic degradation of malachite green dye using chitosan supported ZnO and Ce-ZnO nano-flowers under visible light

Two types of chitosan-based composites (chitosan/ZnO and chitosan/Ce-ZnO composites) were synthesized under microwave irradiation and characterized as advanced catalysts of enhanced photocatalytic activity under the visible light. The morphological investigation reflected the formation of ZnO and Ce doped ZnO at stunning micro flowers of nano limps. Additionally, the optical studies reflected a reduction in the bandgap of ZnO from 3.3 eV to 2.85 eV and 2.5 eV after supporting it onto chitosan chains and after doping it with cerium, respectively. The synthetic composites were applied in photocatalytic removal of malachite green dye under a visible light source. The synthetic CH/ZnO and CH/Ce-ZnO showed enhancement in the photocatalytic removal of M.G by 54% and 87%, respectively, as compared to the pure ZnO. The synthetic composites are of high stability and can be reused for five photocatalytic degradation cycles at stunning removal percentages. The main oxidizing radicals during the removal of M.G by CH/ZnO are the generated electron-hole pairs as well as the hydroxyl radicals. The effective species in CH/Ce-ZnO photocatalytic system are the photogenerated hydroxyl radicals followed by the electron-hole pairs.

A Bi2WO6/Ag2S/ZnS Z-scheme heterojunction photocatalyst with enhanced visible-light photoactivity towards the degradation of multiple dye pollutants

A novel visible-light-driven Z-scheme heterojunction, Bi2WO6/Ag2S/ZnS, was synthesized and its photocatalytic activity was evaluated for the treatment of a binary mixture of dyes, and its physicochemical properties were characterized using FT-IR, XRD, DRS and FE-SEM techniques. The Bi2WO6/Ag2S/ZnS Z-scheme heterojunctions not only facilitate the charge separation and transfer, but also maintain the redox ability of their components. The superior photocatalytic activity demonstrated by the Z-scheme Bi2WO6/Ag2S/ZnS attributes its unique properties such as the rapid generation of electron-hole pairs, slow recombination rate, and narrow bandgap. The performance of the Bi2WO6/Ag2S/ZnS was evaluated for the simultaneous degradation of methyl green (MG) and auramine-O (AO) dyes, while the influences of the initial MG concentration (4-12 mg L-1), initial AO concentration (2-6 mg L-1), pH (3-9), irradiation time (60-120 min) and photocatalyst dosage (0.008-0.016 g L-1) were investigated through the response surface methodology. The desirability function approach was applied to optimize the process and results revealed that maximum photocatalytic degradation efficiency was obtained at optimum conditions including 6.08 mg L-1 of initial MG concentration, 4.04 mg L-1 of initial AO concentration, 7.25 of pH, 90.58 min of irradiation time and 0.013 g L-1 of photocatalyst dosage. In addition, a possible photocatalytic mechanism of the Bi2WO6/Ag2S/ZnS heterojunction was proposed based on the photoinduced charge carriers.

The preparation of thin-walled multi-cavities β-cyclodextrin polymer and its static and dynamic properties for dyes removal

Thin-walled multi-cavities β-cyclodextrin polymers (Hβ-CDs) were prepared by the suspension polymerization method using SiO₂ nanoparticles as a template. The components and morphology structure of Hβ-CDs were characterized by FTIR, BET, SEM, and TEM. The adsorption performances of the prepared nano-adsorbent Hβ-CDs on crystal violet (CV), heavy metal ions, some cationic, neutral, and anionic dyes were investigated. The influences of the pH and ionic strength on CV adsorption by the Hβ-CDs were explored. The correlation coefficient (R²) of pseudo-second-order kinetic model reached 0.9984 and the adsorption isotherm was closer to the Langmuir model. As the temperature increased, the R² of the Freundlich isotherm model rose. Compared to anionic ones and heavy metal ions, Hβ-CDs had a better adsorption efficiency for cationic dyes. Dynamic adsorption also indicated the thin-walled multi-cavities structure was beneficial for improving absorptivity and application of β-cyclodextrin polymers. In addition, the Hβ-CDs exhibited potentially applicable for the regeneration and reuse with the removal efficiency of CV was as high as 89% in the fourth cycle.

Activation of persulfate by CoO nanoparticles loaded on 3D mesoporous carbon nitride (CoO@meso-CN) for the degradation of methylene blue (MB)

A simple and facile synthesis method is developed for the fabrication of CoO loaded ordered mesoporous carbon nitride (CoO@meso-CN) composites, at various CoO loadings, and used, for the first time, to activate persulfate (PS) for methylene blue (MB) degradation. The interfacial interaction between the ultrafine CoO nanoparticles, immobilized by high surface area, regular mesopores, and graphitic nature of the meso-CN support can further enhance the catalytic activation of PS for methylene blue (MB) degradation. Among all catalysts studied, the 5-wt% CoO@meso-CN exhibits the best catalytic performance with a k_obs of 0.264 min^-1. High initial pH, especially at pH-11, is more beneficial for PS activation. Furthermore, the CoO@meso-CN nanocatalyst is highly stable with a consistently high degree of MB degradation and negligible cobalt leaching for at least 5 consecutive catalytic cycles. Both SO₄^- and OH are the major reactive species based on results of EPR and quenching experiments. The degradation intermediates of MB are also identified by HPLC/MS/MS and the possible degradation pathway is proposed. Results clearly demonstrate that CoO@meso-CN is a promising green catalyst with enormous potential for the remediation of hazardous chemicals using PS.

Novel rare earth (RE-La, Er, Sm) metal doped ZnO photocatalysts for degradation of Congo-Red dye: Synthesis, characterization and kinetic studies

Synthesis and characterization of novel ZnO:RE nanostructured materials doped with 1% rare-earth elements (RE = La, Er, Sm) and their testing for photocatalytic applications were reported. The materials were obtained via electrospining, followed by calcination at 700 ^°C. The samples were characterized in terms of surface morphology (SEM, TEM), crystalline structure (XRD) and band gap energies. TEM results showed the formation of a unidimensional structure (ZnO) with an average fiber diameter of 600 nm and a morphology consisting of interconnected nanoparticles having dimensions in the range 25-134 nm (ZnO doped with RE). Optical properties were explored by using UV-VIS reflectance spectra and the band gap values were determined with the Kubelka-Munk function (KM) by plotting [F(R_∞)hν]²vs. hʋ. The photocatalytic activity was assessed by studying the degradation of a water-soluble anionic dye (Congo-Red) under UV-light irradiation. The data related to photodegradation kinetics were reasonably fitted to the pseudo-first-order kinetic model. Results revealed that the values of the rate constants ranged from 10^-3 to 10^-2 min^-1, depending on the material type and initial dye concentration. In addition, Langmuir-Hinshelwood (LH) model was utilized to explain the kinetics of photodegradation reactions of CR in the presence of (ZnO:Sm) sample. The LH approach suggested that both adsorption and photocatalysis phenomena prevailed in the process of dye removal. Optimal conditions of experiments were determined empirically by employing the gradient method. Thus, a maximal value of color removal efficiency (95.8%) was observed experimentally for the initial dye concentration of 10.7 mg/L and 0.236 g/L catalyst dosage (ZnO:Sm). Furthermore, a successful recovery of the spent catalyst was accomplished by thermal activation.

Quirks of dye nomenclature. 11. Safranine and its relatives

Safranine was one of the earliest coal tar dyes following mauveine. By the end of the 19th century, many alkylated derivatives of safranine had been made. The history, identity, names, manufacture, analysis, toxicity, textile dyeing, and biological staining applications, plus some nonstaining uses of safranine, phenosafranine, methylene violet, amethyst violet, azocarmine, and Magdala red are described here.