A coupled electrochemical process for schwertmannite recovery from acid mine drainage: Important roles of anodic reactive oxygen species and cathodic alkaline

• Published in: Journal of hazardous materials Vol. 451; p. 131075
• Main Authors: Huang, Ziyuan, Ma, Huanxin, Liu, Chengshuai, Meng, Fangyuan, Lee, Jyh-Fu, Lin, Yu-Jung, Yi, Xiaoyun, Dang, Zhi, Feng, Chunhua
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 05.06.2023
• Subjects: Acid mine drainage; Adsorption of arsenic species; Fe(II)-activated oxygen reduction; Reactive oxygen species; Schwertmannite synthesis; Reactive oxygen species; Schwertmannite synthesis; Fe(II)-activated oxygen reduction; Acid mine drainage; Adsorption of arsenic species
• ISSN: 0304-3894; 1873-3336; 1873-3336
• DOI: 10.1016/j.jhazmat.2023.131075

The increasing need for sustainable acid mine drainage (AMD) treatment has spurred much attention to strategic development of resource recovery. Along this line, we envisage that a coupled electrochemical system involving anodic Fe(II) oxidation and cathodic alkaline production will facilitate in situ synthesis of schwertmannite from AMD. Multiple physicochemical studies showed the successful formation of electrochemistry-induced schwertmannite, with its surface structure and chemical composition closely related to the applied current. A low current (e.g., 50 mA) led to the formation of schwertmannite having a small specific surface area (SSA) of 122.8 m2 g−1 and containing small amounts of –OH groups (formula Fe8O8(OH)4.49(SO4)1.76), whereas a large current (e.g., 200 mA) led to schwertmannite high in SSA (169.5 m2 g−1) and amounts of –OH groups (formula Fe8O8(OH)5.16(SO4)1.42). Mechanistic studies revealed that the reactive oxygen species (ROS)-mediated pathway, rather than the direct oxidation pathway, plays a dominant role in accelerating Fe(II) oxidation, especially at high currents. The abundance of •OH in the bulk solution, along with the cathodic production of OH−, were the key to obtaining schwertmannite with desirable properties. It was also found to function as a powerful sorbent in removal of arsenic species from the aqueous phase. [Display omitted] •Schwertmannite is synthesized from AMD using a coupled electrochemical system.•The system involves anodic Fe(II) oxidation and cathodic alkaline production.•High currents result in schwertmannite high in SSA and amounts of –OH groups.••OH plays a dominant role in accelerating Fe(II) oxidation at high currents.•Schwertmannite recovered from real AMD is a powerful sorbent for arsenic species.