Effect of chemical modification of algal carboxyl groups on metal ion binding

The use of non-living algal biomass for the extraction of toxic metal ions from wastewaters and mining effluents is reviewed. Acidic methanol was used to esterify the carboxyl groups of 5 different algal biomasses. The extent of carboxyl group modification was monitored by the analysis of methanol released after base hydrolysis of the esterified carboxyls, and the effects of esterification on metal ion binding to the biomass was investigated. Modified biomasses showed major decreases in the binding of copper(II) and aluminium(III), though the decrease varied among algal species. Gold(III) binding capacity slightly increased, indicating that carboxyl groups were responsible for a significant portion of copper(II) and aluminium(III) binding but inhibited the binding of gold(III).