Alternative materials for adsorption of heavy metals and petroleum hydrocarbons from contaminated leachates.

In the present work, waste products from forest industries (sawdust, pine bark and fibre sludge ash), as well as some biological materials (peat, shrimp shells and seaweed), have been investigated with respect to their capacities to adsorb metals and hydrocarbons from contaminated waters. Batch and column experiments were carried out with artificial metal ion solutions and contaminated leachates from an industrial landfill. The fibre sludge ash and the Sphagnum peat showed the highest sorption capacities for metals among the materials studied in batch experiments with single-metal solutions. The uptake of metals by the fibre ash for the metals studied was: Cu and Pb 112 microg g(-1), Zn 115 microg g(-1) and Cr 97 microg g(-1). For peat the uptake was: Pb 109 microg g(-1), Cu 105 microg g(-1), Zn 100 microg g(-1) and Cr 99 microg g(-1). These materials were also effective in adsorption of diesel oil, and the n-alkanes C16 and C12. Peat and ash adsorbed respectively 36.6 and 36.4 mg g(-1) of C12, 1.84 and 1.94 mg g(-1) of C16 and for both 0.98 mg g(-1) of diesel oil. Bark adsorbed diesel oil to 0.83 mg g(-1). In the column experiments, the removal of metals from a contaminated landfill leachate by ash and peat was lower than from artificial solutions with only a few metals. The results suggest interference from other components in the leachates, such as competition of ions for the same active sites. It is quite clear that laboratory tests can overestimate the performance of adsorbents and that experiments should be specific for the intended application. For most of the metals studied in columns, peat appeared to be the best adsorbent, with respect to both sorption capacity and service time. The addition of 10% by weight of fibre ash to the peat gave higher adsorption capacities for Cd, Ni and Pb but lower for the Cu and Zn.