Photoredox catalysis of As(III) by constructed CSnS bonds: Using biomass as templates leads to bio‑carbon/SnS2 nanosheets capable of the efficient photocatalytic conversion of As(III) and calcium arsenate capture

TiO2/Fe2O3 and Fe2O3/TiO2 heterojunction nanocomposites applied to As(III) decontamination

Arsenic contamination in water, particularly in its toxic form As(III), is a significant environmental issue in Brazil and globally. To address this, simple oxides of Fe2O3 and TiO2, along with heterojunction structures TiO2/Fe2O3 and Fe2O3/TiO2, were synthesized using an adapted Pechini method for the decontamination of As(III) via heterogeneous photocatalysis. TiO2 exhibited only the anatase phase, while Fe2O3 showed only the hematite phase (α-Fe2O3). The Fe2O3/TiO2 structure displayed both the hematite and anatase phases, whereas the TiO2/Fe2O3 heterojunction exhibited the anatase, rutile, hematite, and maghemite (γ-Fe2O3) phases. The materials displayed micro/mesoporous characteristics, with surface areas ranging from 20 to 45 m2 g-1, and band gap energies in the range of 2.1 to 3 eV. Hematite was the most effective adsorbent for arsenic. Under UV light irradiation, photolysis achieved 87% oxidation of As(III) in 20 min. The decontamination efficiencies achieved were 63%, 88%, 88%, and 99% for Fe2O3, TiO2, Fe2O3/TiO2, and TiO2/Fe2O3, respectively. Catalyst reuse tests demonstrated excellent stability, with all catalysts maintaining over 80% decontamination efficiency after four cycles. These results highlight the promising potential of TiO2/Fe2O3 heterojunctions for efficient and sustainable As(III) decontamination from contaminated water.

Ball-milling preparation of ZnFe2O4/AgI nanocomposite with enhanced photocatalytic activity

Semiconductor photocatalytic technology is increasingly being utilized in wastewater treatment due to its high efficiency, low energy consumption and environmental friendliness. However, single photocatalysts often exhibit low catalytic performance. In this study, a ZnFe2O4/AgI composite photocatalyst was initially prepared using a high-energy ball-milling method. For the first time, it was applied to the photocatalytic dehydrogenation of diethyl 1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylate (1,4-DHP), as well as photocatalytic degradation of harmful substances such as amaranth (AM), methyl orange (MO) and indole present in wastewater. The composite photocatalyst exhibited superior catalytic performance compared to ZnFe2O4 and AgI under visible light irradiation (λ ≥ 400 nm). With optimized composition, the pseudo-first-order rate constants of ZnFe2O4/AgI-50% were approximately 6, 20, 64 and 38 times higher than that of AgI for the photooxidation of 1,4-DHP, AM, MO and indole, respectively. The enhanced catalytic activity of the composite was attributed to the formation of heterojunction between ZnFe2O4 and AgI, which facilitated the separation and transfer of photogenerated charge carriers. Mechanism studies revealed that photogenerated holes (h+) and superoxide radical anions (˙O2 -) played pivotal roles in the photocatalytic reaction process.

Synthesis of a novel solid mediator Z-scheme heterojunction photocatalysis Fe3O4/C/uio66-nh2: Used for oxidation of Rh6G in water

A novel mediator Z-scheme photocatalyst, Fe3O4/C/UiO-66-NH2, was designed, synthesized, and characterized using SEM, TEM, FTIR, XRD, EPR, and XPS. Formulas #1 to #7 were examined using dye Rh6G dropwise tests. Carbonization of glucose forms the mediator carbon, which connects two semiconductors, Fe3O4 and UiO-66-NH2, to construct the Z-scheme photocatalyst. Formula #1 generates a composite with photocatalyst activity. The band gap measurements of the constituent semiconductors support the mechanisms for the Rh6G degradation using this novel Z-scheme photocatalyst. The successful synthesis and characterization of the proposed novel Z-scheme confirm the feasibility of the tested design protocol for environmental purposes.

Synthesis and Applications of Dimensional SnS2 and SnS2/Carbon Nanomaterials

Dimensional nanomaterials can offer enhanced application properties benefiting from their sizes and morphological orientations. Tin disulfide (SnS₂) and carbon are typical sources of dimensional nanomaterials. SnS₂ is a semiconductor with visible light adsorption properties and has shown high energy density and long cycle life in energy storage processes. The integration of SnS₂ and carbon materials has shown enhanced visible light absorption and electron transmission efficiency. This helps to alleviate the volume expansion of SnS₂ which is a limitation during energy storage processes and provides a favorable bandgap in photocatalytic degradation. Several innovative approaches have been geared toward controlling the size, shape, and hybridization of SnS₂/Carbon composite nanostructures. However, dimensional nanomaterials of SnS₂ and SnS₂/Carbon have rarely been discussed. This review summarizes the synthesis methods of zero-, one-, two-, and three-dimensional SnS₂ and SnS₂/Carbon composite nanomaterials through wet and solid-state synthesis strategies. Moreover, the unique properties that promote their advances in photocatalysis and energy conversion and storage are discussed. Finally, some remarks and perspectives on the challenges and opportunities for exploring advanced SnS₂/Carbon nanomaterials are presented.

Synthesis of a novel solid mediator Z-scheme heterojunction photocatalysis CuFe2O4/Cu/UiO-66-NH2 for oxidation of dye in water

Metal mediator Z-scheme photocatalyst comprises three elements: two semiconductors and a sandwiched metal mediator, so the catalyst can effectively degrade pollutants using visible lights. Proper design and synthesis of Z-scheme with targeted performance has not been systematically proposed. This work proposed the protocol to design and synthesize a Z-scheme photocatalyst with targeted performance. A novel metal mediator Z-scheme photocatalyst CuFe₂O₄/Cu/UiO-66-NH₂ was used to implement the design proposal. After determining synthesis protocol from the theory, the concentrations of three reagents - glucose, l-cysteine, and precursor of UiO-66-NH₂ for synthesizing Z-scheme photocatalyst were revised to achieve successful photocatalyst. Dropwise photocatalytic tests were performed to confirm the activities of the synthesized catalysts using 0.112 mmol/mL UiO-66-NH₂ precursor, 10 mmol/mL glucose, and 1 mmol/mL l-cysteine yielded effective photocatalyst to degrade rhodamine 6G. The dye degradation tests and EPR tests confirmed the successful synthesis of the designed Z-scheme photocatalyst.

Enhanced As(III) transformation and removal with biochar/SnS2/phosphotungstic acid composites: Synergic effect of overcoming the electronic inertness of biochar and W2O3(AsO4)2 (As(V)-POMs) coprecipitation

The activation of carbon atoms in biochar is an important approach for realizing the reuse of discarded woody biomass resources. In this work, a strategy for the construction of carbon-based catalysts was proposed with Magnoliaceae root biomass as a carbon source, doped by SnS₂ and further decorated with heteropoly acid. The introduction of SnS₂ can activate the carbon atom and destroy the electronic inertness of the disordered biochar with 002 planes. In addition, the synergy between the Keggin unit of phosphotungstic acid and biochar/SnS₂ can suppress recombination of e^--h⁺ carriers. The adsorption and photocatalysis experiments results showed that the efficiency of removing As(III) by biochar/SnS₂/phosphotungstic acid (biochar/SnS₂/PTA) systems was 1.5 times that of biochar/SnS₂ systems, and the concentration of total arsenic in the biochar/SnS₂/PTA composite system gradually decreased during the photocatalysis process. The formation of As-POMs can simultaneously realize As(III) photooxidation and As(V) coprecipitation. The phase transfer of arsenic by As-POMs could significantly increase the As adsorption capacity. Specifically, the composites achieved the conversion of S atoms at the interface of biochar into SO₄^•- radicals to enhance the As(III) photooxidation performance.