Abstract:The effect of surfactant polyoxyethylenesorbitan monolaurate (Tween-20) on the nickel bioleaching from pre-treated chromite overburden (COB), Sukinda with fungal strain Aspergillus niger, was examined in shake flasks. Along with the nickel recovery from COB by the fungal bioleaching, the effect of surfactant on the growth of the A. niger was also investigated. Results show that the addition of surfactant in low concentration was favorable for the recovery of nickel from pre-treated COB. Normally, the carbon source (sucrose) in the culture medium was utilized by the A. niger for its cellular metabolism and organic metabolites (bio acids) were produced, which were responsible for the bioleaching of minerals. However, the addition of surfactant (Tween-20) accelerated the rate of sucrose consumption by the fungi, and thus enhancing the extraction of nickel from pre-treated COB. During the study, around 39% nickel extraction was achieved in A. niger mediated bioleaching performed at 2% pulp density of pre-treated COB at 30 °C, in the presence of surfactant whereas only 24% nickel was extracted without surfactant.

Key words: nickel; surfactant; Tween-20; chromite overburden; Aspergillus niger; microbial extraction; bioleaching; cellular metabolism; organic metabolite