Ball-milled magnetite for efficient arsenic decontamination: Insights into oxidation-adsorption mechanism

Abstract

Conventional adsorbents for decontaminating arsenic exhibit low efficacy for the removal of arsenite (As (III)). This study aims to develop a robust As adsorbent from natural magnetite (M-0) via a facile ball milling process, and evaluate their performance for decontaminating As(III) and As(V) in water and soil systems. The ball milling process decreased the particle size and crystallinity of M-0, resulting in pronounced As removal by the ball-milled magnetite (M-m). Ball milling under air facilitated the formation of Fe-OH and Fe-COOH functional groups on M-m interface, contributing to effective elimination of As(III) and As(V) via hydrogen bonding and complexation mechanisms. Synergistic oxidation effects of hydroxyl and carboxyl groups, and reactive oxygen species (O-2(-), and center dot OH) on the transformation of As(III) to As(V) during the adsorption were proposed to explain the enhanced As(III) removal by M-m. A short-term soil incubation experiment indicated that the addition of M-m (10 wt%) induced a decrease in the concentration of exchangeable As by 30.25%, and facilitated the transformation of water-soluble As into residual fraction. Ball milling thus is considered as an eco-friendly (chemical-free) and inexpensive (scalable, one-stage process) method for upgrading the performance of natural magnetite towards remediating As, particularly for tackling the highly mobile As(III).