Removal of zinc ions from aqueous solutions by sorptive-flotation using limestone as a lowcost sorbent and oleic acid as a surfactant

Environmental pollution, mainly in the aquatic systems, due to developments in industry, is one of the most significant problems of this century. Many industrial wastewater streams (ca. the metal working, semiconductor, and copper industries, mine water, etc.) contain heavy metals, which are of great environmental concern and must be removed prior to water discharge or water recycling. The present study aims to develop a simple, rapid and economic procedure for Zn2+ ions removal under the optimum conditions. It is based on the sorption of Zn2+ ions from aqueous solutions onto limestone fines (LS), which is an inexpensive and widespread over the globe, followed by flotation with oleic acid (HOL) surfactant. The different parameters (namely: solution pH, sorbent, surfactant and zinc concentrations, shaking times, ionic strength, temperature and the presence of foreign ions) influencing the sorptive-flotation process were examined. About 100 % of Zn2+ ions were removed from aqueous solutions at pH 7 after shaking for 5 min and at room temperature (～25°C). The procedure was successfully applied to recover almost Zn2+ ions spiked to some natural water samples. A mechanism for sorption -flotation is suggested.