Effect of chemical extractants on the biosorptive properties of pine cone powder: Influence on lead(II) removal mechanism

This study examines the changes in surface properties and lead(II) adsorption mechanism of pine cone powder modified using varying ratios of toluene–ethanol mixtures. Increasing the ratio of toluene in the extractant mixture increased formation of esters and iodine capacity of the material, but reduced carboxylate ions and surface charge. Values of surface charge and iodine capacity showed no relationship with the bulk densities. Maximum lead(II) adsorption was observed for the 2:1 toluene–ethanol modified sample. Lead(II) ions adsorption was inversely related to surface charge and directly related to iodine capacity. Ion-exchange was the dominating mechanism followed by chemisorption. Physical adsorption was higher in the sample modified with the 2:1 mixture which also had the least surface negative charge. Shifts in peaks of FTIR spectra indicate that unbounded –OH and acidic groups were responsible for lead(II) bonding and the contribution of these groups were different for each sample.