ABSTRACT

The efficiency of unmodified (UMGK) and modified (MGK) Garcinia kola pod husk were investigated as adsorbents for removal of Cr(III), Pb(II) and Cd(II) from aqueous solution. Parameters of importance such as pH, adsorbent dosage, initial metal ion concentration, contact time, temperature, and co ions were conducted in batch process to assess sorption capacities of the adsorbent. The adsorption process was optimum for the Cr(III) at pH 6, pH 4 for Pb(II) and pH 6 for Cd(II) in which MGK showed higher sorption capacity 6.0639,5.4981 and 6.1206 respectively from the metal ion. The adsorbent dosage was a determining factor of efficiency in the adsorption pores. In all the three metal ions, increase in dosage increased adsorbent efficiency for both MGK and UMGK. The effect of varying the metal ion concentration showed that the MGK had high sorption capacities as compared to the UMGK while the contact time showed progressive sorption capacities until equilibrium was attained between 90 mins. The effect of temperature indicated that the adsorption process will decrease with increase in temperature for both UMGK and MGK pod husk. The effect of co ions in the batch process indicated a decrease in sorption capacities of the adsorbent. The FTIR analysis revealed some functional group that are possible site of adsorption for the UMGK and the MGK modified spectra introduced an adjusted thiol group. The SEM images correspond to a good surface coverage of the adsorbent. The equilibrium data was analyzed using Languimur and Freudlich isotherm models. The equilibrium indicated the following order of fit for the isotherms Freudlich> Languimur. The pseudo first order and pseudo second order model were used to analyze the kinetics of the adsorption process. The pseudo second order gave the best interpretation of the experimental data. Generally, the UMGK results obtained showed a good sorption capacity and removal efficiency but the MGK had a better sorption capacity. The adsorbent showed affinity for the metal ion in the order Cd (II)> Cr(III)> Pb(II).