STUDI PELEPASAN DAN PENANGANAN KROMIUM DARI AIR LIMPASAN TAMBANG PT VALE INDONESIA Tbk

Abstract

Chromium is generally found in lateritic soils, such as in the nickel mining concession of PT Vale Indonesia Tbk in Sorowako. Sources of chromium in mine water are chromite, olivine, pyroxene and sepentine. While the source of chromium in nickel laterite in the limonite zone is found in chromium-spinel minerals and goethite that bind chromium. Chromium bound in minerals can be oxidized when exposed to water and oxygen (air). This mineral oxidation process produces chromate ions (CrO₄^2-) or better known as hexavalent chromium ions (Cr(VI)). This chromium ion is toxic and soluble in water. Thus, these ions are mobile and have the potential to reduce water quality and health for downstream communities. It is necessary to study the presence of this chromium, then build chromium management units at several mine runoff points to ensure that hexavalent chromium can be reduced to trivalent chromium before being released into the environment. The method used in this study relates to the kinetics of chromium release from the soil and the method of decreasing the concentration of Total Suspended Solid (TSS) after the chromium treatment process using FeSO₄ as a chemical to reduce chromium. In the simulation of chromium release by leaching, it can be seen that both top soil and limonite have high chromium release potential, although the specific chromium release rate in limonite soil is faster than top soil. Processing is carried out using the reductant FeSO₄, to reduce Cr(VI) to Cr(III), with the concentration of Fe added between 2-4 times heavier than the concentration of Cr.