Speciation characterization of arsenic-bearing phase in arsenic sulfide sludge and the sequential leaching mechanisms

• Published in: Journal of hazardous materials 2022-02, Vol.423 (Pt A), p.127035-127035, Article 127035
• Main Authors: Xu, Shenghang, Dai, Siqin, Shen, Yukun, Yu, Tanna, Zhang, Huibin, Cao, Huazhen, Zheng, Guoqu
• Format: Article
• Language: English
• Subjects: Arsenic; Arsenic sulfide sludge; Arsenicals; As-bearing species; Phase constitution; Sequential leaching process; Sewage; Sulfides; Valuable elements
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2021.127035

Arsenic sulfide sludge (ASS) is a kind of deleterious waste which contains various valuable metallic elements, such as Re and Pb, which are always associated with arsenic-bearing phases in ASS. The leaching speed and efficiency of valuable elements may depend on the phase constitution. Here, we proposed a sequential leaching method to thoroughly understand the constitution of arsenic-bearing phase and the distribution of valuable elements in ASS. The results show that five major arsenic-bearing phases exist in ASS: amorphous As2S3, crystalline As4S4, As2O3, and As atoms dissolved into the lattice of PbS and PbSO4 phases. Re is mainly distributed in As2S3 and As4S4 phases. During the leaching process, the dissolution of As2O3 particles and As2O3 layers on the surface of As2S3/As4S4 particles occurs first. Then, the reaction between As2S3/As4S4 particles and copper sulfate happens. The order of leaching sequence is As2O3, amorphous As2S3 and crystalline As4S4. The majority of Re element exists in the solution while almost all Pb element remains in the solid residues, which is beneficial for the separation and purification valuable elements individually. This work not only detailed determines the arsenic-bearing species, but also provides significant theoretical bases for extracting valuable elements from ASS. [Display omitted] •Arsenic-bearing phase in the arsenic sulfide sludge is characterized.•The order of leaching sequence is As2O3, amorphous As2S3 and crystalline As4S4.•As atoms dissolved into the lattice of PbS and PbSO4 phase can not be leached out.•Three leaching stage can be divided according to the leaching speed of arsenic.