Strong Pyro-Electro-Chemical Coupling of Elbaite/H2O2 System for Pyrocatalysis Dye Wastewater

Elbaite is a natural silicate mineral with a spontaneous electric field. In the current study, it was selected as a pyroelectric catalyst to promote hydrogen peroxide (H2O2) for dye decomposition due to its pyro-electro-chemical coupling. The behaviors and efficiency of the elbaite/H2O2 system in rhodamine B (RhB) degradation were systematically investigated. The results indicate that the optimal effective degradability of RhB reaches 100.0% at 4.0 g/L elbaite, 7.0 mL/L H2O2, and pH = 2.0 in the elbaite/H2O2 system. The elbaite/H2O2 system exhibits high recyclability and stability after recycling three times, reaching 94.5% of the degradation rate. The mechanisms of RhB degradation clarified that the hydroxyl radical (·OH) is the main active specie involved in catalytic degradation in the elbaite/H2O2 system. Moreover, not only does elbaite act as a pyroelectric catalyst to activate H2O2 in order to generate the primary ·OH for subsequent advanced oxidation reactions, but it also has the role of a dye sorbent. The elbaite/H2O2 system shows excellent application potential for the degradation of RhB.

Novel Sodium Alginate/Polyvinylpyrrolidone/TiO2 Nanocomposite for Efficient Removal of Cationic Dye from Aqueous Solution

The combination of adsorption and photodegradation processes is an effective technique for the removal of dye contaminants from water, which is motivating the development of novel adsorbent-photocatalyst materials for wastewater treatment. Herein, novel nanocomposite porous beads were developed using titanium dioxide (TiO2) nanotubes embedded in a sodium alginate (SA)/polyvinylpyrrolidone (PVP) matrix using calcium chloride solution as a crosslinker. The prepared nanocomposite beads’ performance was examined as an adsorbent-photocatalyst for the breakdown of methylene blue in aqueous solutions. Several operation factors influencing the dye decomposition process, including photocatalyst dosage, illumination time, light intensity, and stability were investigated. The findings demonstrated that the removal activity of the beads changed with the TiO2 weight ratio in the composite. It was found that SA/PVP/TiO2-3 nanocomposite beads presented the greatest deterioration efficiency for methylene blue dye (98.9%). The cycling ability and reusability of the prepared SA/PVP/TiO2 nanocomposite beads recommend their use as efficient, eco-friendly materials for the treatment of wastewaters contaminated with cationic dyes.

Fabrication, Characterization and Photocatalytic Activity of Copper Oxide Nanowires Formed by Anodization of Copper Foams

In recent paper anodization of copper foams in 0.1 M K2CO3 is reported. Anodization was performed in the voltage range of 5–25 V and in all the cases oxides with a developed surface area were obtained. However, anodizing only at 20 and 25 V resulted in the formation of nanostruc-tures. In all the cases, the products of anodizing consisted of crystalline phases like cuprite (Cu2O), tenorite (CuO), parameconite (Cu4O3) as well as spertiniite (Cu(OH)2). Copper foams after ano-dizing were applied as catalysts in the photocatalytic decolorization of a model organic compound such as methylene blue. The highest photocatalytic activity was observed for samples anodized at 25 V and closely followed by samples anodized at 5 V. The anodized copper foams proved to be a useful material in enhancing the photocatalytic efficiency of organic dye decomposition.

Development of Heavy Metal-Free Photocatalytic RhB Decomposition System Using a Biodegradable Plastic Substrate

The heavy-metal-free photocatalytic system, in which carbon nitride is coated on polylactic acid (PLA) as biodegradable plastic through a simple dip coating method, was used for dye decomposition under visible light irradiation. Solvent selection, solvent concentration, and the number of coatings for dip coating were investigated to optimize the conditions for loading carbon nitride on PLA. Carbon nitride cannot be coated on PLA in water, but it can be strongly coated by decomposing the surface of PLA with ethanol or chlorobenzene to promote physical adsorption and activate surface. The number of dip coatings also affected the photocatalytic decomposition ability. The photocatalytic system was able to decompose the dye continuously in the flow method, and dye (rhodamine B) was decomposed by about 50% at a residence time of 12 min (flow rate 0.350 mL/min) for 30 h.

New Insights into Cd2+/Fe3+ Co-Doped BiOBr for Enhancing the Photocatalysis Efficiency of Dye Decomposition under Visible-Light

Uniform flowerlike microspheres Cd2+/Fe3+ co-doped BiOBr were prepared with the aid of the microwave hydrothermal process. The results indicate that the degradation performance of Bi1−xCdxOBr and Bi1−xFexOBr are 1.31 and 2.05 times that of BiOBr for RhB, respectively. Moreover, the novel Cd2+/Fe3+ co-doped BiOBr photocatalysts with ~0.42 eV impurity bands presented remarkably enhanced photocatalytic activities with being 3.10 times that of pure BiOBr, by achieving e−/h+ efficient separation and narrowed bandgap with the ions synergistic effect of Cd2+ and Fe3+. Based on DFT insights, the photodegradation mechanism was systematically studied that the conversion of multivalent Fe3+ ions promoted the production of •O2−, and Cd2+ ions worked as electron transfer mediators, which elucidated that the •O2− and h+VB mainly participated in the catalytic reaction. The experimental and theoretical results show that the synergistic effects of multi-ion doping have great potential in the field of photocatalysis.