Sorptive–Flotation of Copper(II) from Water Using Different Types of Powdered Activated Carbons as Sorbents and Oleic Acid as Surfactant

Different types of powdered activated carbon, viz. charcoal (PACh), graphite (PG) and three samples (PACI, PACII and PACIII) prepared from olive stones generated as plant wastes and modified with aqueous oxidizing agents, viz. H₂O₂, HNO₃ and (NH₄)₂S₂O₈, were separated from aqueous solution by flotation using oleic acid (HOL) as a surfactant. The effects of initial temperature, initial pH of the suspension, initial carbon and surfactant concentrations, stirring times and the presence of foreign ions on the flotation efficiency of the carbon samples were investigated. Under optimum conditions, separation of the carbon samples was almost complete (~100%).

The separation of Cu^II-loaded carbon was also examined in the presence and absence of sulphide ions as activators. Nearly 100% Cu^II was removed at pH 7 after stirring for 30 min or on raising the temperature of the solution to 30°C or higher. In addition, Cu^II may be separated quantitatively at pH 3 and room temperature if sulphide ions are used as activators. The procedure was extended to the recovery of Cu^II added to some natural water samples. On the basis of IR analyses and neutralization titrations of the surface groups, a mechanism for the sorption and flotation processes is advanced.