XPS study of irreversibly adsorbed arsenic on a Pt(111) electrode

Deep removal of trace arsenic from acidic SbCl3 solution by in-situ galvanically coupled Cu2Sb/Cu particles

Arsenic is a harmful associated element in antimony ore, which might bring out the risk of leakage during complex industrial production of high-purity antimony. Herein, we reported a novel and efficient way to remove the trace arsenic impurity from acidic SbCl3 solution by utilizing copper-system bimetallic particles. Specifically, galvanically coupled Cu2Sb/Cu was in-situ synthesized by introducing precursor copper powder to the specific SbCl3 solution. DFT studies revealed that Sb(III) was easily reduced by Cu to form Cu2Sb due to the strong adsorption of Sb(III) on Cu (111) crystal plane. The Cu2Sb/Cu coupling exhibited excellent activity for As(III) reduction, over 99.4% arsenic were removed under optimal conditions and residual arsenic concentration dropped to only 2.7 mg L-1. Crucially, Sb(III) concentration changes could be neglected. Besides, the dearsenization residues were extensively characterized to analyze the evolvement and cause in the reaction process. The results confirmed that the arsenic removal mechanisms by Cu2Sb/Cu particles were multi-affected, including adsorption, displacement, and precipitation. And the strong electrostatic attraction of AsO+ under high HCl conditions was identified as a key step to achieving dearsenization. This research will provide a theoretical guidance for the green synthesis of high-purity antimony and related products.

Catalytic oxidation mechanism of AsH3 over CuO@SiO2 core-shell catalysts via experimental and theoretical studies

In this study, CuO@SiO₂ core-shell catalysts were successfully synthesized and applied to efficiently remove hazardous gaseous pollutant arsine (AsH₃) by catalytic oxidation under low-temperature and low-oxygen conditions for the first time. In typical experiments, the CuO@SiO₂ catalysts showed excellent AsH₃ removal activity and stability under low-temperature and low-oxygen conditions. The duration of the AsH₃ conversion rate above 90 % for the CuO@SiO₂ catalysts was 39 h, which was markedly higher than that of other catalysts previously reported in the literature. The considerable catalytic activity and stability were attributed to the protection and confinement effects of the SiO₂ shell, which resulted in highly dispersed CuO nanoparticles. Meanwhile, the strong interaction between the CuO core and SiO₂ shell further facilitated the formation of active species such as coordinatively unsaturated Cu²⁺ and chemisorbed oxygen. The accumulation of oxidation products (As₂O₃ and As₂O₅) on the interface between the CuO core and SiO₂ shell and the pore channels of the SiO₂ shell is the main cause of catalysts deactivation. Furthermore, through combined density functional theory (DFT) calculations and characterization methods, a reaction pathway including gradual dehydrogenation (AsH₃*→AsH₂*→AsH*→As*) and gradual oxidation (2As*→As*+AsO*→2AsO*→As₂O₃) for the catalytic oxidation of AsH₃ on CuO (111) surface was constructed to clarify the detailed reaction mechanism. The CuO@SiO₂ core-shell catalysts applied in this study could provide a powerful method for developing AsH₃ catalysts from multiple know AsH₃ removal systems.

Reductive removal of As(V) and As(III) from aqueous solution by the UV/sulfite process: Recovery of elemental arsenic

The removal of arsenic (As(V) and As(III)) from contaminated water has attracted great attention. However, the generation of arsenic-containing hazardous waste by traditional methods has become an inevitable environmental problem. Herein, a UV/sulfite advanced reduction method was proposed to remove As(V) and As(III) from aqueous solution in the form of valuable elemental arsenic (As(0)), thus avoiding the generation of arsenic-containing hazardous waste. The results showed that greater than 99.9% of As(V) and As(III) were reduced to the high purity As(0) (> 99.5 wt%) with the residual arsenic concentration below 10 μg L^-1. The hydrated electrons (e_aq^-), H^• and SO₃^•- radicals are generated by the UV/sulfite process, of which e_aq^- and H^• serve as reductants of As(V) and As(III) while the SO₃^•- radicals inhibit arsenic reduction by oxidizing arsenic. The effective quantum efficiency (Φ) for the formation of As(0) in the As(V) and As(III) removal process is approximately 0.0078 and 0.0055 mol/Einstein, respectively. The reduction of arsenic is favorable under alkaline conditions (pH > 9.0) due to the higher photolysis efficiency of SO₃^2- than HSO₃^- (pK_a = 7.2) and higher stability of e_aq^-/H^• under alkaline conditions. The presence of dissolved oxygen (O₂), NO₂^-, NO₃^-, CO₃^2-, PO₄^3- and humic acid (HA) inhibited arsenic reduction through light blocking or e_aq^-/H^• scavenging effects while Cl^-, SO₄^2-, Ca²⁺ and Mg²⁺ had negligible effects on arsenic reduction. The proposed method can effectively remove and recover arsenic from contaminated water at a low cost, demonstrating feasibility for practical application. This study provides a novel technology for the reductive removal and recovery of arsenic from contaminated water.

Reductive Removal and Recovery of As(V) and As(III) from Strongly Acidic Wastewater by a UV/Formic Acid Process

The removal of arsenic (As(V) and As(III)) from strongly acidic wastewater using traditional neutralization or sulfuration precipitation methods produces a large amount of arsenic-containing hazardous wastes, which poses a potential threat to the environment. In this study, an ultraviolet/formic acid (UV/HCOOH) process was proposed to reductively remove and recover arsenic from strongly acidic wastewater in the form of valuable elemental arsenic (As(0)) products to avoid the generation of hazardous wastes. We found that more than 99% of As(V) and As(III) in wastewater was reduced to highly pure solid As(0) (>99.5 wt %) by HCOOH under UV irradiation. As(V) can be efficiently reduced to As(IV) (H₂AsO₃ or H₄AsO₄) by hydrogen radicals (H^•) generated from the photolysis of HCOOH through dehydroxylation or hydrogenation. Then, As(IV) is reduced to As(III) by H^• or through its disproportionation. The reduction of As(V) to H₄AsO₄ by H^• and the disproportionation of H₄AsO₄ are the main reaction processes. Subsequently, As(III) is reduced to As(0) not only by H^• through stepwise dehydroxylation but also through the disproportionation of intermediate arsenic species As(II) and As(I). With additional density functional theory calculations, this study provides a theoretical foundation for the reductive removal of arsenic from acidic wastewater.

The size effect of Pt nanoparticles: a new route to improve sensitivity in electrochemical detection of As(iii)

The size effect of Pt nanoparticles on detection of arsenic is clarified and the phenomenon is explained by anodic oxygen-transfer reactions and binding energy.