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
Shiwei Liu,Xing Cao,Weichen Yang,Runjie Liu,Lin Fang,Rui Ma,Juan Peng,Shuaifei Zheng,Fei Ji
Higher chlorine (Cl) content than lead (Pb) content in municipal solid waste incineration fly ash (MSWIFA) impeded the practical application of Pb 5 (PO 4 ) 3 Cl-derived magnesium potassium phosphate cement (MKPC) preparation strategy. Herein, Pb/Ca-rich lead slag (LS) was co-blended with MSWIFA to prepare MKPC for the synergistic treatment of both two solid wastes and the Pb-Cl solidification. The results showed that the resulting 15–15 (15 wt% MSWIFA and 15 wt% LS incorporation) sample achieved 25.44 MPa compressive strength , and Pb and Cl leaching toxicity was reduced by 99.18 % and 92.80 %, respectively. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses showed that Pb 2+ , Ca 2+ , phosphate and Cl - formed Pb x Ca 5−x (PO 4 ) 3 Cl in samples. The formation of Pb x Ca 5−x (PO 4 ) 3 Cl was also demonstrated by the high-angle annular dark field scanning transmission electron microscope (HAADF-STEM), while differences in the lattice characteristics of Pb x Ca 5−x (PO 4 ) 3 Cl and Pb 5 (PO 4 ) 3 Cl were found. In-situ XRD indicated that Ca 2+ accelerated the transformation of Pb 2+ to Pb 5 (PO 4 ) 3 Cl. After co-precipitating with Ca 2+ to form Pb x Ca 5−x (PO 4 ) 3 Cl, Pb 2+ continuously substituted Ca 2+ to eventually transform to Pb 5 (PO 4 ) 3 Cl. This work informs the synergistic treatment of MSWIFA and LS and offers new insights into the reaction mechanism between Pb 2+ , phosphate and Cl - under Ca 2+ induction.
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