Isolation and identification of microorganisms causing microbial degradation of organic phase of the solvent extraction unit in the copper industries

Abstract

Solvent Extraction–Electrowinning (SX–EW) is a hydrometallurgical process involving the dissolution and reprecipitation of copper from solution. The organic phases which are widely used in the SX process are very important economically. On the other hand, there are many poisonous components such as phenol in its chemical construction, so its degradation can be critical at economical and environmental point of view. The organic solutions which are used in the Sarcheshmeh Copper Mine consist of LIX 984N as a main extractant and REYSOL 8411, 8401 and kerosene as diluents. The loss of the organic phase from solvent extraction circuits is a major cost factor for SX/EW operations. Recognized sources of loss include evaporation, entrainment, and biological degradation. The mechanisms for both entrainment and evaporative losses are well recognized. Biological degradation of the organic component has not been as extensively evaluated as the other mechanisms but may be a major source of loss. This paper discusses the impact of biological degradation on an operating plant, potential mechanisms for degradation, conditions under which biodegradation of plant organic can occur and plant conditions that may assist in promoting biodegradation. In this research, isolation and identification of microorganisms which are involved in the degradation of the organic phase of the SX unit in the Sarcheshmeh copper mine were investigated. Samples of soil and activated sludge and a sample from an extraction unit were inoculated into microbial culture media containing organic solution as the only carbon source. After growth and isolation of microorganisms, three genera of bacteria, Acinetobacter, Sphingomonas and Moraxella, and two genera of fungi, Aspergillus and Phialophora, were identified.