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 indus- try, is one of the most significant problems of this century. Many industrial wastewater streams (ca. the metal working, semiconductor, and copper in- dustries, mine water, etc.) contain heavy metals, which are of great environmental concern and must be removed prior to water discharge or water recy- cling. The present study aims to develop a simple, rapid and economic procedure for Zn 2+ ions removal under the optimum conditions. It is based on the sorption of Zn 2+ 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 parame- ters (namely: solution pH, sorbent, surfactant and zinc concentrations, shaking times, ionic strength, temperature and the presence of foreign ions) in- fluencing the sorptive-flotation process were ex- amined. About 100 % of Zn 2+ ions were removed from aqueous solutions at pH 7 after shaking for 5 min and at room temperature (~25oC). The proce- dure was successfully applied to recover almost Zn 2+