Kinetics and competitive modeling of cesium biosortion onto chemically modified pine cone powder

The effect of chemical treatment of pine cone with toluene–ethanol mixture on the selectivity, kinetics and mechanism of Cs removal in the presence of electrolytes was examined. Increased hydrophilicity and Cs affinity was observed for treated pine due to organics extraction, increased surface area and formation of carboxylate ions which also produced higher uptake rates for pseudo-first and second order rate constants as compared with the raw pine. Diffusion–chemisorption model better fitted the kinetic data for the treated pine while the pseudo-second order model fitted the raw pine. Cs+, Na+ and Ca2+ ions were found to be adsorbed onto similar sites and the metals were adsorbed in their anhydrous forms. Addition of Na+ and Ca2+ reduced Cs capacity, Cs uptake rate and altered the sorption mechanism. Cs adsorption mechanism was altered by Ca2+ addition and the more porous nature of the treated pine surface. Effect of competition was attributed to ionic radii of Ca2+ (0.99 Å) and Na+ (1.02 Å) which are smaller than Cs+ (1.67 Å).

► Chemical treatment of pine cone to improve surface properties.
► Modeling of Cs adsorption onto raw and chemically treated pine.
► Determining adsorption sites for Cs+, Na+ and Ca2+.
► Comparing kinetic rates constants for single and competitive Cs adsorption.
► Determination of best fitting kinetic models for single and competitive Cs adsorption.