Biosorptive flotation for metal ions removal: the influence of surface tension Original Research Article

The removal of divalent metal ions mixture, such as zinc, copper and nickel, from dilute aqueous solutions or effluents was investigated by applying effectively the intergraded ‘‘biosorptive flotation’’ treatment method. The presence (as alternative cheap sorbent or biosorbent) of nonliving fungi biomass, that is, a waste by-product from industrial fermentation, in a stirred tank contactor was found to assist the removal of toxic metals by adsorption and their subsequent separation by flotation. Parallel laboratory measurements, including surface tension, electrokinetic and contact angle measurements, which are among the major physicochemical parameters influencing this system, were found to correlate quite satisfactorily with the process effectiveness. Under the optimized experimental conditions, the removal of metals by sorption and the recoveries of biomass by flotation were found to be in the order of 95% (or even more) at pH around 7, whereas the surface tension measurements were lowered and the contact angles were increased in this system, hence improving the biomass floatability. On the contrary, although zeta-potential measurements showed a small decrease toward more negative values, this was not found to influence substantially the overall treatment process.