Removal of heavy metals from wastewater effluents by biosorptive flotation

The search for new technologies to remove hazardous metals from wastewaters has focused attention on the metal binding abilities of different biological materials. Various biomaterials have shown promise as sorbents to remove heavy metals from water. Several advantages of peat moss for such applications include its abundance, low, cost, and high metal capacity. Consequently, the adsorption of heavy metals from aqueous solution was studied using a sphagnum peat moss. The adsorption process was found to be pH dependent, and the adsorption capacity increased with initial pH of the solution. The sorption equilibria could be expressed as Freundlich isotherms. The selectivity of the sphagnum pent moss for various heavy metal cations was Pb > Ni > Cu > Cd. The sorption behaviour of cations on the sphagnum peat moss was similar to that of cations on a gel type strong acid resin. Flotation was subsequently shown to be an effective solid-liquid separation process, avoiding the problem for the separation of fine sponge-like moss flocs from the effluent by conventional filtration. A dispersed air flotation column was applied for the generation of fine bubbles to realise the solid-liquid separation. Biosorptive flotation may have practical applications for the removal of hazardous metals from contaminated water supplies. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.