Kinetic studies of competitive heavy metal adsorption by sphagnum moss peat

Much of the work on the adsorption of metals by low-cost, natural biosorbents has focussed on the uptake of single metals. In practice, wastewaters are polluted with multiple metals. In addition, the kinetics of adsorption, which are important in the design of treatment systems, have largely been neglected. This paper describes the results of an examination into the adsorption by peat of copper and nickel from both mono and bi-solute systems. These showed that, in general, pore diffusion appeared to be the rate-controlling step and that the presence of 'contaminant' copper ions reduced the binding of nickel. In fact, the best interpretation which could be placed on the data was that the behaviour of nickel was unusual. The results also showed that the kinetics of adsorption were best described by a second-order expression rather than a first-order model.