Esterified coir pith as an adsorbent for the removal of Co(II) from aqueous solution

Coir pith was chemically modified for the adsorption of cobalt(II) ions from aqueous solution. Chemical modification was done by esterification using succinic anhydride followed by activation with NaHCO3 in order to improve the adsorption of Co(II). Adsorptive removal of Co(II) from aqueous solution onto modified coir pith was evaluated in batch studies under varying conditions of agitation time and metal ion concentration to assess the kinetic and equilibrium parameters. A pseudo-second-order kinetic model fitted well for the sorption of Co(II) onto modified coir pith. Sorption kinetics showed that the loading of Co(II) by this material was quite fast under ambient conditions. The Langmuir and Freundlich equilibrium isotherm models provided excellent fits for the adsorption data, with R2 of 0.99 and 0.98, respectively. After esterification, the maximum Co(II) sorption loading Q0; was greatly improved. It is evident that chemically modified adsorbent exhibits better Co(II) removal capability than raw adsorbent suggesting that surface modification of the adsorbent generates more adsorption sites on its solid surface for metal adsorption. A complete recovery of the adsorbed metal ions from the spent adsorbent was achieved by using 1.0 N HCl.