Preparation of a novel water-soluble organosilane coating and its performance for inhibition of pyrite oxidation to control acid mine drainage at the source

Abstract

Acid mine drainage (AMD) produced by the oxidation of sulfide ore, especially pyrite, pollutes water and soil. Therefore, it is particularly important to control the oxidation of pyrite and the production of acid mine wastewater at the source. Through optimization by orthogonal and conditional tests, the methyltrimethoxysilane (MTMS) coatings successfully formed in a water environment, under the conditions of passivator concentration = 8 v%, hydrolysis pH = 3, hydrolysis temperature = 40 °C, condensation temperature = 50 °C, curing temperature = 80 °C, hydrolysis time = 45 min and condensation time = 100 min. Total Fe content released from the uncoated and coated pyrite with the MTMS coating after chemical oxidation was measured. The results showed that MTMS coating can effectively inhibit the oxidation of pyrite. The release of the total Fe was 10 mg/L after chemical oxidation of 7 h, and the passivation rate reached over 80%. Using ATR-FTIR and XPS, the mechanism of suppression was revealed as a formation of a dense membrane which connected with the surface of pyrite by Fe-O-Si bonds and possessed a cross-linking network of Si–O–Si. The water-based MTMS coating was highly effective in suppressing pyrite oxidation, with great promise for controlling AMD at the source.