In situ treatment of acidic arsenic-containing wastewater from the non-ferrous metal smelting industry has been a great challenge for cleaner production in smelters. Scorodite and iron arsenate have been proved to be good arsenic-fixing minerals; thus, we used lead slag as an iron source to remove arsenic from wastewater by forming iron arsenate and scorodite. As the main contaminant in wastewater, As(III) was oxidized to As(V) by H2O2, which was further mineralized to low-crystalline iron arsenate by Fe(III) and Fe(II) released by lead slag (in situ generated). The calcium ions released from the dissolved lead slag combined with sulfate to form well-crystallized gypsum, which co-precipitated with iron arsenate and provided attachment sites for iron arsenate. In addition, a silicate colloid was generated from dissolved silicate minerals wrapped around the As-bearing precipitate particles, which reduced the arsenic-leaching toxicity. A 99.95% removal efficiency of arsenic with initial concentration of 6500 mg/L was reached when the solid–liquid ratio was 1:10 and after 12 h of reaction at room temperature. Moreover, the leaching toxicity of As-bearing precipitate was 3.36 mg/L (As) and 2.93 mg/L (Pb), lower than the leaching threshold (5 mg/L). This work can promote the joint treatment of slag and wastewater in smelters, which is conducive to the long-term development of resource utilization and clean production.Keywords:arsenic wastewater;lead slag;iron arsenate;scorodite
Pyrrhotite is a potential source of S 2 − for the sulfide precipitation of nonferrous metal ions in hydrometallurgy and waste water treatment . In this study, different pyrrhotite crystals were prepared using zero-valent iron and sulfur to determine the effects of the pyrrhotite's structure on the sulfide precipitation of copper ions. The results indicate that the sulfide precipitation of copper ions highly depends on the crystal structure and crystallinity of pyrrhotite. Monoclinic pyrrhotite was found to be the most effective for copper sulfide precipitation, which can be used for the selective precipitation of copper ions from arsenic wastewater. More than 96% copper ions were removed with little loss of arsenic, contributing to a copper product of 20.2% Cu and 0.7% As, which can serve as raw materials of copper metallurgy. X-ray diffraction analysis showed the presence of CuS and (Cu x Fe 1 − x )S, indicating that most copper ions precipitated as CuS and some copper ions entered the FeS lattice by a lattice substitution reaction. Therefore, monoclinic pyrrhotite may provide an alternative solution for the selective precipitation of copper from arsenic wastewater.
Sun Xiaolei,Li Qiao,Shen Jinyou,Han Weiqing,Li Jiansheng,Sun Xiuyun
In this study, we report the co-treatment of municipal solid waste incineration fly ash and high arsenic-containing wastewater. The appropriate liquid-solid ratio for co-treatment and the feasibility of co-treatment with 5000 mg/L arsenic in wastewater were investigated, as well as the risk of heavy metals leaching from the co-treated products in the actual leachate. Further, a new index for assessing the risk of heavy metals releasing into the environment was proposed. The results demonstrated that the optimal liquid-solid ratio was 10 mL/ 20 g, considering that it allowed the maximum co-treatment amount of wastewater and would not affect the subsequent disposal of co-treated products in landfills. In the presence of 5000 mg/L arsenic in wastewater, the chemical speciation distribution and leaching toxicity of As, Cr, Cu, and Pb in the co-treated products would not change significantly. The leaching results of co-treated products in actual leachate indicated that the co-treated products can favor the stabilization of As, Cr, and Pb in leachate. The migration and transformation index value of Cu suggested the risk of Cu releasing in a leachate scenario. Through co-treatment, wastewater can be completely absorbed into the fly ash without the need for further treatment, featuring significant economic and environmental benefits. Graphical Abstract
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