A novel 3D heteropoly blue type photo-Fenton-like catalyst and its ability to remove dye pollution

Advances in Polyoxometalates as Electron Mediators for Photocatalytic Dye Degradation

The increasing concerns over the environment and the growing demand for sustainable water treatment technologies have sparked substantial interest in the field of photocatalytic dye removal. Polyoxometalates (POMs), known for their intricate metal-oxygen anion clusters, have received considerable attention due to their versatile structures, compositions, and efficient facilitation of photo-induced electron transfers. This paper provides an overview of the ongoing research progress in the realm of photocatalytic dye degradation utilizing POMs and their derivatives. The details encompass the compositions of catalysts, catalytic efficacy, and light absorption propensities, and the photocatalytic mechanisms inherent to POM-based materials for dye degradation are exhaustively expounded upon. This review not only contributes to a better understanding of the potential of POM-based materials in photocatalytic dye degradation, but also presents the advancements and future prospects in this domain of environmental remediation.

Design and synthesis of three new copper coordination polymers: efficient degradation of an organic dye at alkaline pH

Three new coordination polymers (CPs) based on Cu(II), namely {[Cu₆(H₂L)₄(4,4'-bpy)₆(H₂O)₂]·16H₂O}_n(1), {[Cu(H₃L)(1,4-bib)]·3H₂O}_n(2), and {[Cu₂(H₂L)₂(1,4-bib)₂][Cu(1,4-bib)(H₂O)₂]}_n·4nH₂O(3) (H₅L = 6-(3',4'-dicarboxyphenoxy)-2,3,5-benzene tricarboxylic acid, 4,4'-bpy = 4,4'-bipyridine and 1,4-bib = 1,4-bis(1H-imidazol-1-yl)benzene) were synthesized under hydrothermal conditions and characterized. 1 adopts a three-dimensional structure and can be described with the point symbol {4·5²}₂{4²·5⁴·6⁴·8³·9²}{5·10⁴·12} whereas 2 shows a layered structure. 3 can be perceived as a complex salt of two coordination polymers: the cationic component [Cu(1,4-bib)(H₂O)₂]_n²⁺ (3a) represents a chain polymer and the second anionic moiety [Cu₂(H₂L)₂(1,4-bib)₂]_n^2- (3b) corresponds to a 2D sub-structure. In the presence of H₂O₂, all complexes 1-3 act as efficient photocatalysts for the degradation of the dye methylene blue (MB). The effects of properties such as initial MB concentration, catalyst dosage, pH value, and H₂O₂ concentration on MB degradation were also investigated and analyzed in detail. Compounds 1-3 exhibit excellent structural stability during the catalytic process and can be reused at least three times. The hydroxyl radical (OH˙) and holes (h⁺) were confirmed as the main active species in the degradation process.

Removal of Phenol from Steel Plant Wastewater in Three Dimensional Electrochemical (TDE) Process using CoFe2O4@AC/H2O2

This study investigated the removal of phenol from steel industry wastewater by three dimensional electrochemical (TDE) process using CoFe2O4 nanobiocomposite based activated carbon in the presence of H2O2 (EC-CoFe2O4@AC-H2O2). In this study, CoFe2O4 nanobiocomposite-foundation activated carbon (CoFe2O4@AC) was used as microelectrode, adsorbent, and activator for peroxide hydrogen. The removal efficiency of phenol and COD was investigated through the parameters of pH, contact time, CoFe2O4@AC dosage, current density, and H2O2 concentration. The highest removal rates of phenol and COD were >99% and 98%, respectively. Also, steel plant wastewater under the optimal conditions of pH = 6.5, current density = 15 mA cm−2, contact time = 25 min, H2O2 concentration of 1.0 mM, and CoFe2O4@AC dose = 0.3 g L−1. Kinetic analysis revealed that the adsorption experimental data was best fitted by the pseudo-first-order model.

Fabrication and Highly Efficient Dye Removal Characterization of Beta-Cyclodextrin-Based Composite Polymer Fibers by Electrospinning

Dye wastewater is one of the most important problems to be faced and solved in wastewater treatment. However, the treatment cannot be single and simple adsorption due to the complexity of dye species. In this work, we prepared novel composite fiber adsorbent materials consisting of ε-polycaprolactone (PCL) and beta-cyclodextrin-based polymer (PCD) by electrospinning. The morphological and spectral characterization demonstrated the successful preparation of a series of composite fibers with different mass ratios. The obtained fiber materials have demonstrated remarkable selective adsorption for MB and 4-aminoazobenzene solutions. The addition of a PCD component in composite fibers enhanced the mechanical strength of membranes and changed the adsorption uptake due to the cavity molecular structure via host⁻guest interaction. The dye removal efficiency could reach 24.1 mg/g towards 4-aminoazobenzene. Due to the admirable stability and selectivity adsorption process, the present prepared beta-cyclodextrin-based composite fibers have demonstrated potential large-scale applications in dye uptake and wastewater treatment.

Novel flexible Fenton-like catalyst: Unique CuO nanowires arrays on copper mesh with high efficiency across a wide pH range

Free-standing and flexible Cu@CuO nanowires (NWs) mesh as an easily recycled Fenton-like catalyst is developed for the first time. Dense CuO nanowire arrays were uniformly grown on a copper mesh surface simply by wet etching accompanied with thermal dehydration. These dense CuO NWs provide a large specific area and therefore guarantee excellent catalytic performance toward the degradation of rhodamine B (RhB). With a k-value of 0.23 min^-1, such a Cu@CuO NWs mesh is able to degrade 100% RhB in only 16 min. This Fenton-like catalyst is also appropriate for degrading other organic dyes, including crystal violet, methylene blue, and rhodamine 6G. Unlike the conventional Fenton catalyst implemented at a pH value around 3, the Cu@CuO NWs mesh could adapt to a wide pH range from 2.1 to 12.0. More intriguingly, the Cu@CuO NWs mesh with excellent flexibility could be easily recycled after catalysis, which is a significant advance compared to the previously reported Fenton catalysts in the form of powders or nanoparticles. In addition, the recycling performance of this Cu@CuO NWs mesh was also assessed. On the basis of electron spin resonance (ESR) results, O^2- rather than OH is the main active species for the dye degradation by the Cu@CuO NWs mesh. With a marvelous combination of excellent flexibility, wide pH adaptation, and high efficiency, this easily recycled three dimensional Cu@CuO NWs architecture can afford new ideas for the Fenton chemistry.

EDTA-Fe(III) Fenton-like oxidation for the degradation of malachite green

Industrial waste, urban sewage and aquaculture have led to severely increased grades of environment pollutants such as dyes, pesticides and fertilizer. The use of technologies for purifying contaminated waters can be difficult and toxic due to the anti-photolysis, anti-oxidation and anti-bio-oxidation characteristics of organic pollutants, and there is therefore a significant need for new approaches. Here, we report methods of Fenton oxidation and EDTA-Fe(III) Fenton-like oxidation which can be used to degrade malachite green (MG: a dye and antibiotic-like substance) from contaminated water. Compared with the degradation rate (59.34%) of the Fe(III)/H₂O₂ Fenton process, the EDTA-Fe(III) Fenton-like oxidation got a better degradation rate (92.7%) at neutral pH conditions. By conducting a series of parallel controlled experiments (changing parameters such as the reactant concentration, temperature, and pH), we report the relationships between the degradation effect and different parameters, and we fitted their pseudo first order kinetic curves. Furthermore, we repeated to adjustment of the concentrations of MG in solutions to test the cycle performance and catalytic activities of EDTA-Fe(III)/H₂O₂ system and it showed good repeatability in the first five rounds and all of them keep the degradation efficiencies greater than 80%. By conducting comparative spin-trapping electron paramagnetic resonance (EPR) experiments, we showed indirectly that the OH contributes to the degradation of MG. Additionally, the results of the EPR experiments showed that EDTA contributes to the generation of OH in the EDTA-Fe(III)/H₂O₂ Fenton-like system. By conducting total organic carbon (TOC) analysis experiments, we found that EDTA was also oxidized to some extent during the degradation of MG. In all, the findings of this work widen the range of the optimal pH values up to neutral condition for degradation of MG by use of EDTA-Fe(III) Fenton-like system. And this system could be used as one approach for the degradation of organic pollutants at neutral conditions and provide some initial information regarding EDTA-Fe(III) Fenton-like oxidations. It's significant for the expansion of the homogenous Fenton-like family and its application in the field of water treatment.

Flexible 3D Fe@VO2 core-shell mesh: A highly efficient and easy-recycling catalyst for the removal of organic dyes

Nowadays, it is extremely urgent to search for efficient and effective catalysts for water purification due to the severe worldwide water-contamination crises. Here, 3D Fe@VO₂ core-shell mesh, a highly efficient catalyst toward removal of organic dyes with excellent recycling ability in the dark is designed and developed for the first time. This novel core-shell structure is actually 304 stainless steel mesh coated by VO₂, fabricated by an electrophoretic deposition method. In such a core-shell structure, Fe as the core allows much easier separation from the water, endowing the catalyst with a flexible property for easy recycling, while VO₂ as the shell is highly efficient in degradation of organic dyes with the addition of H₂O₂. More intriguingly, the 3D Fe@VO₂ core-shell mesh exhibits favorable performance across a wide pH range. The 3D Fe@VO₂ core-shell mesh can decompose organic dyes both in a light-free condition and under visible irradiation. The possible catalytic oxidation mechanism of Fe@VO₂/H₂O₂ system is also proposed in this work. Considering its facile fabrication, remarkable catalytic efficiency across a wide pH range, and easy recycling characteristic, the 3D Fe@VO₂ core-shell mesh is a newly developed high-performance catalyst for addressing the universal water crises.