Suppression of Arsenopyrite Surface Oxidation by Coating with MTMOS Sol-Gel Film: An Electrochemical Characterization

Abstract

Oxidation of arsenopyrite (FeAsS) in mine tailings is considered as the major cause of arsenicreleasing in groundwater around mine sites. The oxidation rate is accelerated by the biooxidation ofchemolithotropes bacteria, such as Acidithiobacillus ferrooxidans via the adsorption mechanism.Hence, coating with thin films as a physical barrier for oxidants approaching the mineral surface isone of the effective abatement strategies. In preliminary work, we confirmed the effectiveness ofmethyltrimethoxysilane (MTMOS) coating by biochemical and chemical oxidations. In this work, weexamined the effectiveness by the technique of the resistance of MTMOS film coated on arsenopyriterod under immersion in 3 wt% NaCl electrolyte with electrochemical impedance spectroscopy (EIS).The coating resistance was 108 ohm/cm2 and slightly decreased to a steady state value around 107ohm/cm2 after 3 d immersion.

Keywords : Arsenopyrite / Sol-Gel / Acidithiobacillus ferrooxidans / Electrochemical ImpedanceSpectroscopy (EIS) / Methyltrimethoxysilane (MTMOS)