Evaluation of tea-derived biosurfactant on removing heavy metal ions from dilute wastewater by ion flotation

The potential of ion flotation to remove cadmium, lead and copper from dilute aqueous solution with a plant-derived biosurfactant tea saponin was investigated. The operating parameters, such as initial solution pH, the collector to heavy metals ratio, and the ionic strength (NaCl), have a marked influence on the performance of ion flotation, as shown in this investigation. The maximum removal of lead, copper and cadmium can reach 89.95%, 81.13% and 71.17%, respectively when the ratio of collector to metal was 3:1. The selectivity coefficients of lead over cadmium, lead over copper and cadmium over copper in the present of tea saponin were observed, and the selectivity coefficient of lead over cadmium was the highest one. The foam products were identified by Fourier transform infrared (FTIR) spectroscopy, and the result indicated that the carboxylate groups and divalent metal ions were formed definite complexation in the bulk solution. (C) 2007 Elsevier B.V. All rights reserved.