Degradation of methylene blue in a heterogeneous Fenton reaction catalyzed by chitosan crosslinked ferrous complex

Polymer-Supported Heterogeneous Fenton Catalysts for the Environmental Remediation of Wastewater

Materials based on polymer hydrogels have demonstrated potential as innovative Fenton catalysts for treating water. However, developing these polymer-supported catalysts with robust stability presents a significant challenge. This paper explores the development and application of polymer-supported heterogeneous Fenton catalysts for the environmental remediation of wastewater, emphasizing the enhancement of metal incorporation into catalysts for improved efficiency. The study begins with an introduction to the heterogeneous Fenton process and its relevance to wastewater treatment. It further delves into the specifics of polymer-supported heterogeneous Fenton catalysts, focusing on iron oxide, copper complexes/nanoparticles, and ruthenium as key components. The synthesis methods employed to prepare these catalysts are discussed, highlighting the innovative approaches to achieve substantial metal incorporation. Operational parameters such as catalyst dosage, pollutant concentration, and the effect of pH on the process efficiency are thoroughly examined. The catalytic performance is evaluated, providing insights into the effectiveness of these catalysts in degrading pollutants. Recent developments in the field are reviewed, showcasing advancements in catalyst design and application. The study also addresses the stability and reusability of polymer-supported heterogeneous Fenton catalysts, critical factors for their practical application in environmental remediation. Environmental applications are explored, demonstrating the potential of these catalysts in addressing various pollutants. The Conclusions offers future perspectives, underlining the ongoing challenges and opportunities in the field, and the importance of further research to enhance the efficacy and sustainability of polymer-supported heterogeneous Fenton catalysts for wastewater treatment.

Preparation of Activated Carbon-Reinforced Composite Beads Based on MnO2/MCM-41@Fe3O4 and Calcium Alginate for Efficient Removal of Tetracycline in Aqueous Solutions

Tetracycline (TC) is a common antibiotic; when untreated TC enters the environment, it will cause a negative impact on the human body through the food chain. In the present study, MnO2/MCM-41@Fe3O4 (FeMnMCM) prepared using a hydrothermal and redox method and Camellia oleifera shell-activated carbon (COFAC) prepared through alkali activation were encapsulated using alginate (ALG) and calcium chloride as a cross-linking matrix to give the composite beads COFAC-FeMnMCM-ALG. The resultant COFAC-FeMnMCM-ALG composite beads were then carefully characterized, showing a high immobilization of MnO2/MCM-41@Fe3O4, with porous COFAC as an effective bioadsorbent for enriching the pollutants in the treated samples. These bead catalysts were subsequently applied to the oxidative degradation of TC in a Fenton oxidation system. Several parameters affecting the degradation were investigated, including the H2O2 concentration, catalyst dosage, initial TC concentration, and temperature. A very high catalytic activity towards the degradation of TC was demonstrated. The electron paramagnetic resonance (EPR) and quenching results showed that ·OH and ·O2- were generated in the system, with ·OH as the main radical species. In addition, the COFAC-FeMnMCM-ALG catalyst exhibited excellent recyclability/reusability. We conclude that the as-prepared COFAC-FeMnMCM-ALG composite beads, which integrate MnO2 and Fe3O4 with bioadsorbents, provide a new idea for the design of catalysts for advanced oxidation processes (AOPs) and have great potential in the Fenton oxidation system to degrade toxic pollutants.

Synthesis of the MnO2-Fe3O4 catalyst support on amorphous silica: a new Fenton's reagent in the degradation of the reactive blue-19 in aqueous solution

In this study, a new Fenton's reagent was synthesized via two steps: (1) the dispersed Fe₃O₄ nanoparticles were immobilized on the surface of the SiO₂ carrier via the precipitation process, and (2) the MnO₂ nano-sheets were coated on the surface of Fe₃O₄/SiO₂ via hydrothermal method. The SiO₂ carrier has been synthetically utilized from Vietnamese rice husk. The successful formation of the MnO₂-Fe₃O₄/SiO₂ composite has been analytically characterized by the XRD (X-ray diffraction), SEM (scanning electron microscope), EDS (energy dispersive spectrometry)-mapping, FTIR (Fourier transform infrared), S_BET (Brunauer-Emmett-Teller specific surface area), and adsorption/desorption isotherms. This Fenton system was employed to catalyze degradation process of the reactive-blue 19 (RB19) with approximately 100% of removal efficiency after 25 min at the optimal condition of 0.15 g/100 mL of catalyst dosage, pH = 3, and the H₂O₂ concentration of 3 mL/100 mL. Moreover, the catalyst could be reused at least six times with high catalytic activity that was more than 90%. In conclusion, this study showed that the mesoporous MnO₂-Fe₃O₄/SiO₂ composite has a great potential for the removal application of dyes from wastewater, and the application of Vietnam rice husk in environmental treatment was developed.

Glucose-Activated Nanoconfinement Supramolecular Cascade Reaction in Situ for Diabetic Wound Healing

Supramolecular nanofunctional materials have attracted increasing attention from scientific researchers due to their advantages in biomedicine. Herein, we construct a nanosupramolecular cascade reactor through the cooperative interaction of multiple noncovalent bonds, which include chitosan, sulfobutylether-β-cyclodextrin, ferrous ions, and glucose oxidase. Under the activation of glucose, hydroxyl radicals generated from the nanoconfinement supramolecular cascade reaction process are able to initiate the radical polymerization process of vinyl monomers to form hydrogel network structures while inhibiting resistant bacterial infection. The results of the diabetic wound experiment confirmed the capacity of the glucose-activated nanoconfinement supramolecular cascade reaction in situ for potent antimicrobial efficacy and wound protection. This strategy of "two birds with one stone" provides a convenient method for the application of supramolecular nanomaterial in the field of biomedicine.

Visible-Light-Driven Bio-Templated Magnetic Copper Oxide Composite for Heterogeneous Photo-Fenton Degradation of Tetracycline

The development of a visible-light-driven, reusable, and long-lasting catalyst for the heterogeneous photo-Fenton process is critical for practical application in the treatment of contaminated water. This study focuses on synthesizing a visible-light-driven heterogenous bio-templated magnetic copper oxide composite (Fe3O4/CuO/C) by a two-step process of bio-templating and hydrothermal processes. The prepared composite was characterized by field emission-scanning electron microscope (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), electrical impedance spectroscopy (EIS), and vibrating sample magnetometer (VSM). The results reveal that the prepared composite retains the template’s (corn stalk’s) original porous morphology, and a substantial amount of CuO and Fe3O4 particles are loaded onto the surface of the template. The prepared Fe3O4/CuO/C composite was employed as a catalyst for heterogeneous photo-Fenton degradation of tetracycline (TC) irradiated by visible light. The prepared Fe3O4/CuO/C catalyst has high efficiency towards TC degradation within 60 min across a wide pH range irradiated by visible light, which is attributed to its readily available interfacial boundaries, which significantly improves the movement of photoexcited electrons across various components of the prepared composite. The influence of other parameters such as initial H2O2 concentration, initial concentration of TC, and catalyst dosages was also studied. In addition to high efficiency, the prepared catalyst’s performance was sustained after five cycles, and its recovery is aided by the use of an external magnetic field. This research paper highlights the development of a heterogeneous catalyst for the elimination of refractory organic compounds in wastewater.

Fe-chitosan complexes for oxidative degradation of emerging contaminants in water: Structure, activity, and reaction mechanism

Versatile and ecofriendly methods to perform oxidations at near-neutral pH are of crucial importance for processes aimed at purifying water. Chitosan, a deacetylated form of chitin, is a promising starting material owing to its biocompatibility and ability to form stable films and complexes with metals. Here, we report a novel chitosan-based organometallic complex that was tested both as homogeneous and heterogeneous catalyst in the degradation of contaminants of emerging concern in water. The stoichiometry of the complex was experimentally verified with different metals, namely, Cu(II), Fe(III), Fe(II), Co(II), Pd(II), and Mn(II), and we identified the chitosan-Fe(III) complex as the most efficient catalyst. This complex effectively degraded phenol, triclosan, and 3-chlorophenol in the presence of hydrogen peroxide. A putative ferryl-mediated reaction mechanism is proposed based on experimental data, density functional theory calculations, and kinetic modeling. Finally, a film of the chitosan-Fe(III) complex was synthesized and proven a promising supported heterogeneous catalyst for water purification.

Starch, cellulose, pectin, gum, alginate, chitin and chitosan derived (nano)materials for sustainable water treatment: A review

Natural biopolymers, polymeric organic molecules produced by living organisms and/or renewable resources, are considered greener, sustainable, and eco-friendly materials. Natural polysaccharides comprising cellulose, chitin/chitosan, starch, gum, alginate, and pectin are sustainable materials owing to their outstanding structural features, abundant availability, and nontoxicity, ease of modification, biocompatibility, and promissing potentials. Plentiful polysaccharides have been utilized for making assorted (nano)catalysts in recent years; fabrication of polysaccharides-supported metal/metal oxide (nano)materials is one of the effective strategies in nanotechnology. Water is one of the world's foremost environmental stress concerns. Nanomaterial-adorned polysaccharides-based entities have functioned as novel and more efficient (nano)catalysts or sorbents in eliminating an array of aqueous pollutants and contaminants, including ionic metals and organic/inorganic pollutants from wastewater. This review encompasses recent advancements, trends and challenges for natural biopolymers assembled from renewable resources for exploitation in the production of starch, cellulose, pectin, gum, alginate, chitin and chitosan-derived (nano)materials.

Treatment of methyl orange by the catalytic wet peroxide oxidation process in batch and continuous fixed bed reactors using Fe-impregnated 13X as catalyst

Fe-impregnated 13X (Fe-13X) catalysts were prepared for catalytic wet peroxide oxidation (CWPO) of methyl orange (MO) solution in batch and continuous fixed bed reactors. A systematical study was carried out to investigate the influence of the main operating parameters on the batch reactor performance. The kinetic curves were analyzed by using a pseudo-first-order kinetic equation over the 30-70 °C temperature range. In addition, the effects of catalysts filling amount and feed flow rate on the catalytic performance of Fe-13X catalysts in a fixed bed reactor were studied. The experimental results showed that the Fe-13X catalysts achieved the highest activity (100% MO conversion and 74.5% chemical oxygen demand (COD) elimination ratio, respectively) at 25 min with trace mount of Fe leaching concentration (<2.1 mg/L) at the optimized reaction conditions (namely 1.0 g/L catalyst concentration, pH 2.0, 17.6 mM H₂O₂, 70 °C) in a batch reactor. Kinetic studies showed that two different reaction regions existed, and an activation energy of 51.9 kJ/mol for the second region was found. Under the optimal operating conditions found (namely, catalysts filling amount of 3.5 g, feed flow rate of 4 mL/min), the Fe-13X catalysts displayed high MO conversion (99.4%) and COD elimination ratio (77.1%) after continuously ran for 200 min in a fixed bed reactor.

Functionalizing bottom ash from biomass power plant for removing methylene blue from aqueous solution

In order to seek a possible path for utilization bottom ash, the solid waste from biomass incineration for power generation, its basic characteristics were investigated, and removing methylene blue (MB) from aqueous solution was attempted as well. Results indicated bottom ash dominantly contained Si and Ca-related minerals with >35 mineral elements, meanwhile, it was typically characterized by alkalinity (pH of 9.5) and low specific surface area (14.5m²/g). As the only bottom ash was employed for removing MB, removal efficiency was lower than 44%, however, it was greatly improved to 100% as hydrogen peroxide was supplemented (final concentration of 4.0%). Based on the elucidated mechanisms, Fenton-like reaction was triggered by bottom ash, which was dominantly responsible for removing MB, rather than the adsorption by bottom ash. Besides, increasing reaction temperature and duration dramatically promoted MB removal by bottom ash with the aid of hydrogen peroxide (HBA). A great promotion on MB removal from 92.3mg/g to 143.9mg/g was achieved as pH was adjusted from 2.0 to 5.0, indicating MB removal was pH-dependent. The maximum removal of 260.9mg/g was achieved by HBA at a relatively high initial MB concentration of 2000.0mg/L, suggesting a great potential in treating dye wastewater by functionalizing bottom ash with the aid of hydrogen peroxide. Moreover, the released heavy metals and derived by-products from MB removal were acceptable in consideration of their potential environmental risks. Thus, the current work offers a new path to valorize the solid waste in biomass electricity generation plant.

Preparation of magnetite nanoparticles by high-energy planetary ball mill and its application for ciprofloxacin degradation through heterogeneous Fenton process

In this study, the heterogeneous Fenton oxidation of ciprofloxacin (CIP) in an aqueous solution was examined over the nano-sized magnetite (Fe₃O₄) as a catalyst supplied through high-energy planetary ball milling process. To characterize the magnetite samples after and before ball milling operation, the X-ray diffraction (XRD), High-resolution scanning electron microscopy (HR-SEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET) and Fourier transform infrared spectroscopy (FTIR) analysis were applied. The catalytic properties of the magnetite were considerably improved because of the enhancement in its physical properties, resulted from milling process. The findings also indicated that 6 h ball-milled magnetite demonstrated better properties for elimination of CIP of about 89% following 120 min reaction at optimal conditions of H₂O₂ 12 mM, Fe₃O₄ 1.75 g L^-1, CIP 10 mg L^-1 and pH 3.0. The effects of various operational parameters, including the initial pH of the solution, H₂O₂ initial concentration, catalyst dosage, milling time and CIP initial concentration was investigated. Application of organic and inorganic scavengers considerably decreased the CIP removal efficiency. Correspondingly, with respect to the leached iron values at pH 3, it was concluded that CIP elimination was mainly occurred through heterogeneous Fenton procedure. This process included the adsorption and oxidation phases in which the hydroxyl radicals (OH) played a significant role. GC-MS analysis was used for recording of the generated intermediates of the CIP removal in the course of heterogeneous Fenton process.