Application of Fe2V4O13 as a new multi-metal heterogeneous Fenton-like catalyst for the degradation of organic pollutants

Copper(II) containing chitosan hydrogel as a heterogeneous Fenton-like catalyst for production of hydroxyl radical: A quantitative study

The Fenton reaction, which generate hydroxl radical as a powerful oxidizing agent, is of interest due to its role in biological systems and wastewater treatment. However, unlike the ferrous/ferric system that is active only in acidic condition, the copper ion can operate over a wide pH range as a Fenton-like system. In this research a copper containing hydrogel (Cu/CH) was prepared by loading the Cu²⁺ ions into a hydrogel based on chitosan, acrylamide (AAM), and acrylic acid (AA), and used for production of hydroxyl radical in a Fenton-like reaction. The prepared catalyst was characterized by using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and energy dispersive X-ray analysis (EDAX). The catalytic activity of the hydrogels was quantitatively investigated by measuring the hydroxyl radical using the photoluminescence (PL) technique. Various parameters such as contact time, amount of metal ion, dose of hydrogen peroxide, and dose of Cu/CH were investigated. A catalytic mechanism was proposed for production of hydroxyl radical. The reusability studies showed that the Cu/CH can be reused several times without loss of its catalytic activity. In addition, various metal ions were loaded into the hydrogel and their performance in the production of hydroxyl radical were investigated.

Binary and Ternary Vanadium Oxides: General Overview, Physical Properties, and Photochemical Processes for Environmental Applications

This review article is a comprehensive report on vanadium oxides which are interesting materials for environmental applications. Therefore, a general overview of vanadium and its related oxides are presented in the first two parts. Afterwards, the physical properties of binary and ternary vanadium oxides in single and mixed valence states are described such as their structural, optical, and electronic properties. Finally, the use of these vanadium oxides in photochemical processes for environmental applications is detailed, especially for the production of hydrogen by water splitting and the degradation of organic pollutants in water using photocatalytic and photo-Fenton processes. The scientific aim of such a review is to bring a comprehensive tool to understand the photochemical processes triggered by vanadium oxide based materials where the photo-induced properties are thoroughly discussed based on the detailed description of their intrinsic properties.

A microwave-activated coal fly ash catalyst for the oxidative elimination of organic pollutants in a Fenton-like process

Raw coal fly ash was first activated by microwave irradiation to promote its catalytic potential and then used as a Fenton-like catalyst to treat polyacrylamide-contaminated wastewater. The optimal activation conditions of the raw coal fly ash (microwave power = 700 W, irradiation time = 10 min, mixing speed = 120 rpm, and raw coal fly ash loading = 20 g L-1) were determined by the orthogonal test. The significance of each effective parameter follows the order: raw coal fly ash loading > microwave power > irradiation time > mixing speed. Microwave irradiation can change the surface morphology and remarkably increase the specific surface area and pore volume. More than 75% of the TOC in the polyacrylamide-contaminated wastewater can be removed under the optimized treatment conditions ([H2O2] = 12 mg L-1, catalyst loading = 10 g L-1, [polyacrylamide] = 200 mg L-1, T = 313 K). The kinetic study shows that the variation in the catalyst loading and the polyacrylamide concentration can change the degradation path of the polyacrylamide, whereas the variation in the H2O2 dosage can accelerate the degradation of polyacrylamide. The Fenton-like process studied herein has a wider optimal pH range (2-5) than that of the classic Fenton process (3). The catalyst has weak catalytic capacity but better catalytic persistence than that of Fe2+. During the five runs of the catalyst, some heavy metallic and toxic elements (Fe, Al, Ti, Cr, Mn, etc.) can be detected but under the limits of the GB8978-1996 standard. Leaching can weaken the catalytic capacity (i.e., stability) of the catalyst. The catalytic process is caused by the synergism of multiple metals and consists of heterogeneous and homogeneous processes.

Magnetic multi-metal co-doped magnesium ferrite nanoparticles: An efficient visible light-assisted heterogeneous Fenton-like catalyst synthesized from saprolite laterite ore

Magnetic nanoparticles of multi-metal co-doped magnesium ferrite (MgFe₂O₄) were synthesized from saprolite laterite ore by a hydrothermal method, and firstly proposed as a heterogeneous photon-Fenton-like catalyst for degradation of Rhodamine B (RhB). The factors that influence the degradation reaction including pH value, the concentration of H₂O₂ and the amount of catalyst, were systematically investigated. The doped MgFe₂O₄ exhibited a degradation efficiency up to 96.8%, and the chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiencies about 85.6% and 68.3%, respectively, under visible light illumination for 180min. The high activity is mainly attributed to the high specific surface area of the catalyst and the synergistic interaction between photo-catalytic oxidation and Fenton-like oxidation. Moreover, the catalyst also showed good stability and recycling performance for degrading RhB. After five consecutive degradation cycles, the activity decayed no more than 10%. Compared to other catalysts prepared from pure chemical agents, the multi-metal co-doped MgFe₂O₄ is more competitive due to its high activity, good stability, ease of recollection, and especially the use of saprolite laterite ore as precursor. This work may provide a new avenue to synthesize efficient ferrite catalysts for degrading organic pollutants in wastewater by using natural minerals.

SrCo1-xTixO3-δ perovskites as excellent catalysts for fast degradation of water contaminants in neutral and alkaline solutions

Perovskite-like oxides SrCo_1-xTi_xO_3-δ (SCT_x, x = 0.1, 0.2, 0.4, 0.6) were used as heterogeneous catalysts to activate peroxymonosulfate (PMS) for phenol degradation under a wide pH range, exhibiting more rapid phenol oxidation than Co₃O₄ and TiO₂. The SCT_0.4/PMS system produced a high activity at increased initial pH, achieving optimized performance at pH ≥ 7 in terms of total organic carbon removal, the minimum Co leaching and good catalytic stability. Kinetic studies showed that the phenol oxidation kinetics on SCT_0.4/PMS system followed the pseudo-zero order kinetics and the rate on SCT_0.4/PMS system decreased with increasing initial phenol concentration, decreased PMS amount, catalyst loading and solution temperature. Quenching tests using ethanol and tert-butyl alcohol demonstrated sulfate and hydroxyl radicals for phenol oxidation. This investigation suggested promising heterogeneous catalysts for organic oxidation with PMS, showing a breakthrough in the barriers of metal leaching, acidic pH, and low efficiency of heterogeneous catalysis.

Selective Fenton-like oxidation of methylene blue on modified Fe-zeolites prepared via molecular imprinting technique

A facile strategy to increase the selectivity of heterogeneous Fenton oxidation is investigated. The increase was reached by increasing selective adsorption of heterogeneous Fenton catalyst to a target pollutant. The heterogeneous Fenton catalyst was prepared by a two-step process. First, zeolite particles were imprinted by the target pollutant, methylene blue (MB), in their aggregations, and second, iron ions were loaded on the zeolite aggregations to form the molecule imprinted Fe-zeolites (MI-FZ) Fenton catalyst. Its adsorption amount for MB reached as high as 44.6 mg g^-1 while the adsorption amount of un-imprinted Fe-zeolites (FZ) is only 15.6 mg g^-1. Fenton removal efficiency of MI-FZ for MB was 87.7%, being 33.9% higher than that of FZ. The selective Fenton oxidation of MI-FZ for MB was further confirmed by its removal performance for the mixed MB and bisphenol A (BPA) in solution. The removal efficiency of MB was 44.7% while that of BPA was only 14.9%. This fact shows that molecular imprinting is suitable to prepare the Fe-zeolites (FZ)-based Fenton catalyst with high selectivity for removal of target pollutants, at least MB.

Factorial experimental design application in modification of volcanic ash as a natural adsorbent with Fenton process for arsenic removal

This paper describes an experimental design technique for the modification of volcanic ash with Fenton reagent (FMVA) to be used as a natural adsorbent in the removal of As(III) and As(V) from aqueous solution. The influence of pH, contact time and Fe(2+)/H2O2 on arsenic removal by the modified volcanic ash was investigated. It was observed that the arsenic removal efficiency was influenced by two of these parameters. The Fe(2+)/H2O2 ratio is an important factor that affects both As(III) and As(V) adsorption (P = 0.000). The pH affects As(V) adsorption (P = 0.003) more significantly than As (III) adsorption (P = 0.02). It was observed that the maximum As(III) adsorption by the FMVA was obtained at pH 2, Fe(+2)/H2O2 = 0.06 and 30 min of contact time (39 microg As(III) per mg FMVA), whereas the maximum As(V) adsorption was obtained under the conditions of pH 5, Fe(+2)/H2O2 = 0.06 and 30 min of contact time (41 microg As(V) per mg FMVA).

Simultaneous degradation of refractory contaminants in both the anode and cathode chambers of the microbial fuel cell

In this study, the microbial fuel cell (MFC) was combined with the Fenton-like technology to simultaneously generate electricity and degrade refractory contaminants in both anode and cathode chambers. The maximum power density achieved was 15.9 W/m(3) at an initial pH of 3.0 in the MFC. In the anode chamber, approximately 100% of furfural and 96% COD were removed at the end of a cycle. In the cathode chamber, the Fenton-like reaction with FeVO(4) as a catalyst enhanced the removal of AO7 and COD. The removal rates of AO7 and COD reached 89% and 81%, respectively. The optimal pH value and FeVO(4) dosage toward degrading AO7 were about 3.0 and 0.8 g, respectively. Furthermore, a two-way catalyst mechanism of FeVO(4) and the contaminant degradation pathway in the MFC were explored.