The Study of Inhibition of Arsenopyrite Oxidation by Coating Treatment

Abstract

The chemical and biochemical oxidation of arsenopyrite caused the release of arsenic to environment.In this work, we studied the inhibition arsenopyrite oxidation by coating with sodium silicate. In the experiment,0.001M Na₂SiO₃.9H₂O at pH 1, 3, 5 and 7 was used to coat on the particles (size < 300 μm or average size145 μm) of arsenopyrite mineral. We chose pH at pH 3 and 5 as appropriate condition for the coating since theamount of iron and arsenic detected in solution was less than other condition (Fe conc. < 0.02 ppm, As conc.< 0.05 ppm) Arsenopyrite particles coated with 0.001M Na₂SiO₃.9H₂O at pH 3 and 5 were subject to test forthe surface resistance to chemical oxidation by 0.145M H₂O₂ at pH 2, 4 and 5. It was found surface coating atpH 3 resisted to chemical oxidation superior than that of coating at pH 5. In the microbial adsorption experimenton arsenopyrite coated and uncoated surfaces using Thiobacillus ferrooxidans, it demonstrated that there wassome difference in the number adsorbed cells. Since the adsorption followed the Langmuir adsorption isotherm,therefore we could analyze the maximum adsorption capacity (XAM) of the particle surface. It was found XAMfor the coated and uncoated arsenopyrite surface was 4.710 x 10⁹ and 7.231 x 10⁹ cells/g of FeAsS respectively.So we concluded that coated sodium silicate suppressed the adsorption of Thiobacillus ferrooxidans.

Keywords : Coating / Oxidation / Arsenopyrite / Thiobacillus ferrooxidans /Langmuir Adsorption Isotherm