Arsenic removal from hydrometallurgical waste sulfuric acid via scorodite formation using siderite (FeCO3)

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 424; p. 130552
• Main Authors: Su, Rui, Ma, Xu, Yin, Xiuling, Zhao, Xiaoming, Yan, Zelong, Lin, Jinru, Zeng, Xiangfeng, Zhang, Danni, Wang, Shaofeng, Jia, Yongfeng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.11.2021
• Subjects: Arsenic; Scorodite; Siderite; Stability; Waste sulfuric acid; Waste sulfuric acid; Scorodite; Stability; Arsenic; Siderite
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2021.130552

[Display omitted] •An economical and efficient method for the treatment of As in WSA is proposed.•The removal efficiency of As from WSA can reach up to 99.99%.•The leaching concentration of As of products is as low as 0.13 mg/L.•Different iron arsenate phases formed during the reaction.•Both ferric arsenate and adsorbed As contribute to the high As removal efficiency. High concentration of arsenic (As) in waste sulfuric acid (WSA) generated from hydrometallurgical mineral processing must be removed and immobilized for protecting local environments. However, the economical and efficient treatment method for WSA is still lacking. We proposed the precipitation of As in WSA as scorodite by using economical siderite (FeCO3) as an Fe source through a three-step process. Firstly, the WSA is neutralized to pH ~ 1 with Ca(OH)2 via precipitation of gypsum with low As content (~ 7.1 × 10-2 < 1 g/kg As). Secondly, As(III) in the WSA is oxidized to As(V) with H2O2. Thirdly, the produced As(V) is immobilized as scorodite through a mutual cycle composed of siderite dissolution-oxidation by O2(g) and Fe(III)-As(V) precipitation-crystallization. Slow dissolution-oxidation of siderite produces a low supersaturation of Fe(III), ensuring the continuous Fe(III)-As(V) precipitation as well as scorodite crystallization. Under the optimal condition (pHinitial = 1.1, Fe/As = 2, Temperature = 95 °C, and Time = 10 h), the removal efficiency of As in WSA reached up to 99.99%. The produced solid residue displayed a good stability with leaching As concentration as low as 0.13 mg/L via the TCLP methods due to the formation of different ferric arsenate minerals and the adsorption of As on undissolved siderite and FeOOH minerals. Our findings provide an economical method for safe treatment of As-bearing hydrometallurgical WSA and shed new light on the understanding of As-Fe precipitation in acidic solution.