Enhancing AsH3 Detoxification via Electron-Deficient [NiIII-OH (µ-O)] in a Nickel-Modified NaY Zeolite: A Pathway toward As0 Products.

The transformation of toxic arsine (AsH3) gas into valuable elemental arsenic (As0) from industrial exhaust gases is important for achieving sustainable development goals. Although advanced arsenic removal catalysts can improve the removal efficiency of AsH3, toxic arsenic oxides generated during this process have not received adequate attention. In light of this, a novel approach for obtaining stable As0 products was proposed by performing controlled moderate oxidation. We designed a tailored Ni-based catalyst through an acid etching approach to alter interactions between Ni and NaY. As a result, the 1Ni/NaY-H catalyst yielded an unprecedented proportion of As0 as the major product (65%), which is superior to those of other reported catalysts that only produced arsenic oxides. Density functional theory calculations clarified that Ni species changed the electronic structure of oxygen atoms, and the formed [NiIII-OH (µ-O)] active centers facilitated the adsorption of AsH2*, AsH*, and As* reaction intermediates for As-H bond cleavage, thereby decreasing the direct reactivity of oxygen with the arsenic intermediates. This work presents pioneering insights into inhibiting excessive oxidation during AsH3 removal, demonstrating potential environmental applications for recovery of As0 from toxic AsH3.

Removal of SO2 from smelting flue gas by using copper tailings with MnSO4: factors optimization by response surface methodology.

The abatement of SO2 and the utilization of copper tailings are identified as two attention-attracting environmental issues in the copper smelter. In this study, to improve the flue gas desulfurization performance and the utilization of copper tailings, SO2 removal from smelting flue gas by using copper tailings combined with MnSO4·H2O was investigated. The effects of operation variables, including inlet SO2 concentration, absorption temperature, slurry concentration, and MnSO4·H2O amount, on the flue gas desulfurization performance were studied based on the response surface method. It was found that the effect of operation variables on SO2 removal follows the descending order: the inlet SO2 concentration, MnSO4·H2O concentration, absorbent temperature, and solid-liquid ratio. The interaction between the inlet SO2 concentration and MnSO4·H2O concentration is an important factor for breakthrough sulfur capacity. Elevated temperature and high initial SO2 concentration inhibited the efficient removal of SO2. Moreover, a proposed equation exhibits good consistency in the prediction for the breakthrough sulfur dioxide capacity. Therefore, the results can provide a reliable reference and basis for industrial application for flue gas desulfurization with copper tailings.

Leaching of iron from copper tailings by sulfuric acid: behavior, kinetics and mechanism.

Copper tailing is a widespread and intractable solid waste in copper production. Traditional leaching and recovery technology for copper tailing focuses on copper but neglects the leaching of iron. With the increase in applications and demands of iron-containing materials for environment, understanding the leaching behaviors of iron can promote the utilization of copper tailings. In this study, the kinetics and mechanism of the leaching of iron from copper tailings using sulfuric acid were studied. Under optimal conditions (40 °C, sulfuric acid concentration of 0.53 mol L-1, stirring speed of 400 rpm, solid/liquid ratio of 1 : 10 and leaching time of 120 min), 66.45% of Fe, along with 65.32% of Zn and 59.95% of Cu, were leached from the tailings. The leaching of iron was confirmed to be controlled by solid-film diffusion. The reaction orders for sulfuric acid concentration, solid/liquid ratio, and stirring speed were found to be 0.85, -0.70, and 0.40, respectively. Results from XRF, XRD, and SEM indicated that oxides (including CaO, CuO, and ZnO) were leached first, after which Fe2SiO4 was preferentially reacted compared to Fe3O4. The accumulation of CaSO4 and SiO2 inhibited the further leaching of iron.