MODEL OF THE FORMATION OF CR(VI) FROM LATERITIC NICKEL ORE AND ITS FACTORS

• Main Author: Clementine da Costa, Janice
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/87985
• Institution: Institut Teknologi Bandung

Chromium is an element that humans need in limited quantities to help metabolism, but there are chromium ions that have carcinogenic effects and are harmful to humans, namely the six-valent chromium ion, Cr(VI). The presence of Cr(VI) found in surface water flows near nickel laterite mining areas is a concern because it can be a source of contaminants for the surrounding area and its potential to contaminate groundwater aquifers. In an effort to determine the potential for Cr(VI) pollution in laterite nickel mining areas, especially in voids and sediment ponds, laboratory-scale research was conducted with an experimental approach to determine the factors that influence the formation of Cr(VI). Simulations were conducted for ten days on two nickel laterite ores from different sources which were then soaked by rainwater. Data collection on the physical-chemical properties of water was carried out every day and water samples were taken for laboratory testing to see changes in the physical-chemical properties of water and changes in the chemical composition of water, especially dissolved metals in water including total Cr and Cr(VI). The results of laboratory measurements and tests show that laterite nickel ores containing many serpentine minerals and alterations produce more Cr that can be oxidized to Cr(VI), especially in limonite and saprolite, while bedrock cannot release Cr during the simulation. The factor that determines the formation of Cr(VI) is the pH of the water, where an alkaline pH can oxidize Cr and keep Cr(VI) stable but the pH of rainwater can only oxidize Cr(VI) in FeOxrich environments. The duration of UV irradiation and the presence of O2 gas favor the formation of Cr(VI) in greater amounts in FeOx-rich environments, indicating that Cr(VI) enrichment in water interacting with laterite nickel ore outcrops is formed through photochemical oxidation processes.