Effect of pH on oxygen-induced abio-oxidation and removal of As from As-rich acid mine drainage in the co-existence of Zn(II). (May 2022)

• Record Type: Journal Article
• Authors: Yuan, Zidan; Lin, Jinru; Ma, Xu; Yu, Le; Zhang, Peiwen; Wang, Shaofeng; Jia, Yongfeng
• Is Part Of: Applied geochemistry. Volume 140(2022)
• Publication Date: 2022-05
• Subjects: As-rich AMD -- Co-existent Zn(II) -- Abio-oxidation -- Removal -- Stability; Environmental geochemistry -- Periodicals; Water chemistry -- Periodicals; Geochemistry -- Social aspects -- Periodicals; Geochemistry -- Periodicals; 551.9
• DOI: 10.1016/j.apgeochem.2022.105298
• Languages: English
• ISSNs: 0883-2927

Abstract

Abstract: Zn(II) enhances the adsorption of arsenate in heavy metal wastewater onto iron oxides, but the effect of Zn(II) on the removal of As during the oxidation of As(III) to As(V), corresponding to remediation of As-rich acid mine drainage (AMD) via oxidation-precipitation method, is still unclear. The rapid and efficient removal of As from As-rich AMD in the co-existence of Zn(II) was conducted through oxygen-induced abio-oxidation of Fe(II) and As(III) at slightly acidic to alkaline pH in this work. After 8-h reactions, arsenic removal and arsenite oxidation efficiencies reached 91.9–99.9% and 34.6–63.8%, which showed an evident rise at first and then decreased as the pH increased from 3 to 9. Maximum As removal and oxidation with the As-leaching stable solid product was observed at pH 5. Reactive oxygen species (ROS) contents involving Fenton-like reaction degree and solid product species were controlled by pH for As(III), As(V), Fe(II), Fe(III) and Zn(II) liquid-solid distribution as the probable mechanism. Almost all of arsenic and zinc were mainly immobilized by the produced Zn(II)–As(III + V)-bearing SO4 -ferrihydrite at pH 5 with the higher short-term stability of the final solid due to higher As(V) in solid-phase and a small amount of zinc hydrogen arsenate produced. At higher pH, adsorbed-Zn(II) competition with ROS for solid surface sites negatively affected the Fenton-like reaction process for unstable Zn(II)–As(III + V)-bearing magnetite, causing the decrease of As removal and oxidation. Highlights: pH is important to the removal of As from As-rich AMD in the co-existence of Zn(II). 91.9–99.9% and 34.6–63.8% of As removal and oxidation occur in 8 h at pH 3–9. pH 5 is optimal for maximum As removal and oxidation with lowest As-leaching solid. Zn(II)–As(III + V)-bearing SO4 -ferrihydrite is mainly formed for As fixation at pH 5. Zn(II) existence promote the increase of the stability of the solid product at pH 5.