Adsorption of heavy metals from electroplating wastewater by wood sawdust

Abstract

Poplar wood sawdust was examined for adsorption as a replacement for current, more expensive methods of removing copper, zinc and cadmium from electroplating wastewater. Langmuir, Freundlich, BET and competitive Langmuir (two competing ions) isotherms were fitted to experimental data and the goodness of their fit for adsorption was compared. The shapes of isotherms obtained fitted well with multilayer adsorption. This was established and confirmed through solid correspondence between the BET equation and experimental data, in contrast to an observed monolayer adsorption of metal ions on poplar sawdust in single metal–water solutions. The adsorption of copper ions from a mixture (in wastewater) was better than that from a single metal solution. The adsorptions of zinc ions from wastewater and from model water were approximately equal, while that of cadmium ions was significantly lower from the wastewater than from model water. The aforementioned suggests that the presence of other ions in wastewater hindered adsorption of cadmium ions.