Self-enhanced and efficient removal of arsenic from waste acid using magnetite as an in situ iron donator. (15th June 2019)

• Record Type: Journal Article
• Authors: Cai, Guiyuan; Zhu, Xing; Li, Kongzhai; Qi, Xianjin; Wei, Yonggang; Wang, Hua; Hao, Fengyan
• Is Part Of: Water research. Volume 157(2019)
• Page Start: 269
• Page End: 280
• Publication Date: 2019-06-15
• Subjects: Arsenic -- Waste acid -- Magnetite -- Scorodite -- Leaching toxicity; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2019.03.067
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: High arsenic-containing waste acid from the heavy nonferrous metallurgical sector (Cu, Pb, Zn, Ni, Sn, etc.), one of the most dangerous arsenic hazardous wastes with extremely high arsenic concentrations, has presented enormous challenges to the environment and caused severe environmental pollution over the past few decades due to the lack of affordable and environmentally friendly disposal technologies. Here, we report a green process for the self-enhanced and efficient removal of arsenic from waste acid using magnetite as an in situ iron donator. Firstly, the room-temperature predissolution of magnetite in waste acid provides initial iron ions as a starting precipitator of arsenic, simultaneously providing a suitable pH range and an active surface that are ready for the nucleation and growth of scorodite. Afterwards, arsenic is precipitated in form the of scorodite, which is driven by a mutually improved cycle composed of arsenic precipitation and magnetite dissolution on the surface of magnetite particles. This cycle creates a low supersaturation of iron and constant pH in the waste acid, ensuring the continuous precipitation of arsenic as well-crystallized and environmentally stable scorodite by using magnetite as an in situ iron donator via the reaction of 2Fe3 O4 + 6H3 AsO4 + H2 O2 = 6FeAsO4 + 10H2 O. Under optimal conditions, including a 6-h room-temperature predissolution, a 12-h atmospheric reaction at 90 °C and a pH of 2.0 with a magnetite dosage at the Fe3 O4 /As molar ratio (the molar ratio of Fe3 O4 in magnetite to As in waste acid) of 1.33, 99.90% of arsenic was successively removed from waste acid with an initial arsenic concentration of 10300 mg/L. In combination with the good adaptability of this process, the performed case study and prospective process show the successful removal of arsenic from waste acid as well as great potential for large-scale applications. Graphical abstract: Image 102 Highlights: Arsenic removal from waste acid using magnetite as in situ iron source. Mutually-improved relationship of arsenic precipitation and magnetite dissolution. Prospective process for the effective treatment of arsenic-containing waste acid.