Stabilization treatment of arsenic-alkali residue (AAR): Effect of the coexisting soluble carbonate on arsenic stabilization

• Published in: Environment international 2020-02, Vol.135, p.105406-105406, Article 105406
• Main Authors: Wang, Xin, Ding, Jiaqi, Wang, Linling, Zhang, Shuyuan, Hou, Huijie, Zhang, Jingdong, Chen, Jing, Ma, Miao, Tsang, Daniel C.W., Wu, Xiaohui
• Format: Article
• Language: English
• Subjects: Arsenate minerals; Arsenic stabilization; Arsenic-alkali residue; Coexisting soluble carbonate; Ferrous sulfate; Lime
• ISSN: 0160-4120; 1873-6750
• DOI: 10.1016/j.envint.2019.105406

[Display omitted] •Ferrous iron is more efficient and greener than lime for As stabilization in AAR.•Formation of arsenate minerals is the predominant stabilization mechanism.•Coexisting carbonate has a slight effect on As stabilization by ferrous iron.•As stabilization by lime is severely blocked by coexisting carbonate. Arsenic-alkali residue (AAR) from antimony smelting is highly hazardous due to its ready leachability of As, seeking for proper disposal such as stabilization treatment. However, As stabilization in AAR would be challenging due to the high content of coexisting soluble carbonate. This study conducted the stabilization treatments of AAR by ferrous sulfate and lime, respectively, and revealed the significant influence of coexisting carbonate. It was found that ferrous sulfate was more efficient than lime, which required only one-tenth of dosages of lime to reduce the As leaching concentration from 915 mg/L to a level below 2.5 mg/L to meet the Chinese regulatory limit. The combining qualitative and quantitative analyses based on XRD, SEM–EDS, and thermodynamic modeling suggested that the formation of insoluble arsenate minerals, ferrous arsenate or calcium arsenate, was the predominant mechanism for As stabilization in the two treatment systems, and their efficiency difference was primarily attributed to the coexisting carbonate, which had a slight effect on ferrous arsenate but severely obstructed calcium arsenate formation. Moreover, the examination of As leaching concentrations in 1-year-cured samples indicated that the long-term stability of ferrous sulfate treatment was far superior to that of lime treatment. This study provides ferrous salts as a promising and green scheme for stabilization treatment of AAR as well as other similar As-bearing solid wastes with coexisting soluble carbonate.