Abstract

This paper discusses the kinetics of lead (II) and Nickel (II) ions adsorption from aqueous solutions using chemically modified and unmodified agricultural adsorbents at 28°C, pH 6.2 and 0.01M NaCl ionic strength.  The removal of the two metals were found to increase with increase in chemical modification, the sequence being 1.0MOPF>0.5MOPF>UOPF.  In addition Nickel (II) had a higher percentage removal than lead (II). The intraparticle diffusion rate constant (K_id) were determined to be 63.023 min^-1 (Ni²⁺) and 38.212 min^-1 (Pb²⁺) for the 1.0MOPF adsorbent. The results show that the intraparticle diffusion model fits the sorption of lead (II) with higher coefficient of determination (r²) than Nickel (II), thereby indicating that the intra-particle diffusion may be the rate limiting step for Pb²⁺sorption.  The results from this study indicates that a good adsorbent for the removal of Ni²⁺ and Pb²⁺ can be obtained from both chemically modified and unmodified oil palm fruit  fibre.

Key words: oil palm fruit fibre, mercaptoacetic acid, intraparticle diffusion, adsorbent, chemical modified and agricultural-by-product.

Abbreviation

a, constant in intraparticle diffusion model depicts adsorption mechanism; C_o, initial metal ion concentration (mgL^-1); C_t, concentration of metal ion at time t (mgL^-1); K_id, intraparticle diffusion rate constant (min^-1); R_em, percentage of metal removed; 1.0MOPF, 1.0 M mercaptoacetic acid modified oil palm fruit fibre; 0.5MOPF, 0.5 M mercapto-acetic acid modified oil palm fruit fibre; and UOPF, unmodified oil palm fruit fibre.