Recovery of Metals and Stabilization of Arsenic from (Bio-)Leaching Operations by Engineered Biological Processes

Abstract

This paper focuses on the application of biotechnological stabilization of arsenic from (bio-) leaching operations. One of the latest applications of the Thioteq technology is arsenic immobilization. The Thioteq-scorodite biorecovery reactor is an aerobic system to immobilise arsenic in bio-scorodite crystals. In this patented process, biological arsenite oxidation, biological ferrous iron oxidation and crystallisation reactions are simultaneously taking place. Bio-scorodite crystals can be easily harvested by sedimentation due to their relative large size of up to 160 μm. This biogenic material is classified as non-hazardous due to its very low arsenic leaching rates. Furthermore, bioscorodite crystals resemble the colour, crystal morphology, iron and arsenic content, structural water of the mineral scorodite. The operational costs related to scorodite bio-crystallization can be reduced at least 50% compared to chemical precipitation because the use of biological reactions to induce the crystallization of scorodite and the good stability properties of the produced crystals. The Thioteq-scorodite process is a reliable cost effective solution to arsenic removal and immobilization by using biological processes. The stabilization of arsenic in the form of biologically produced scorodite is an attractive technology for the compact and safe immobilization of arsenic from medium to high concentrations of arsenic in acidic process streams.