Removal of Cadmium(II) from Aqueous Solution by Ion Flotation Using Rhamnolipid Biosurfactant As an Ion Collector

In this research, the potential of cadmium removal from aqueous solution by foam flotation with a rhamnolipid biosurfactant sample was studied. The effects of different major operating conditions, such as rhamnolipid and cadmium concentrations, solution pH, aeration rate, and frother type and concentration, on the cadmium removal were investigated. The selectivity coefficients in the presence of rhamnolipid maintained definite orders as follows: cadmium > zinc, cadmium > copper, and zinc > copper. The selectivity coefficient of cadmium over copper was the highest one. The maximum removals of Cd from clean and Zn- and Cu-contaminated solutions were about 57%, 36%, and 48%, respectively. Kinetic studies indicated that ion flotation of cadmium follows a first-order equation with a kinetic rate of 0.0071 min(-1). Although the removals are rather low, it seems that the use of rhamnolipid biosurfactant can be promising in heavy-metal removal from wastewaters by foam flotation with some modifications.