The ion flotation of copper, nickel, and cobalt using the biosurfactant surfactin

Abstract

Heavy metal contaminated waters are a significant environmental hazard, which require novel treatment methodologies. Further, the metals which might be recovered from these streams have significant intrinsic value, if they can be collected and concentrated. This work demonstrates, for the first time, the use of surfactin, an environmentally benign biosurfactant, for the flotation of metal ions (Cu2+, Ni2+, and Co2+). Surfactin, at a molar ratio of 1:3, has been shown to float 75.2%, 94.7%, and 98.2% of initial 100 μ M solutions of copper nickel and cobalt, respectively. Increasing the gas flow rate modifies the float by increasing the carryover of water into the overflow. A pH of 5 was found to be ineffective (due to surfactin precipitation), while a pH of 10 was less effective than pH 7, likely due to the ionic speciation of the metals in solution tending to hydroxyl precipitates at a high pH. This work demonstrates an opportunity for the recovery of metals (at low concentrations) using biosurfactant-based froth flotation.