ABSTRACT

Heavy metals which are directly discharged into receiving water bodies pollute and make them unsafe for use because of their extreme harmful effects on man. Adsorption is one of the effective methods for the removal of heavy metal ions from waste water. This work investigates the potential of a cheap and readily available adsorbent, the seeds of velvet tamarind in adsorbing Pb²⁺, Cu²⁺ and Fe²⁺ from aqueous solution. The effects of various parameters such as adsorbent dose, temperature, initial concentration, pH and contact time for adsorption of lead, copper and iron ions from aqueous solutions by tamarind seeds were examined. The experimental equilibrium adsorption data were tested using the Langmuir, Freundlich, Halsey and Harkins-Jura equations and their constants and correlation coefficients determined. Freundlich model showed the best fit to the experimental data as assessed from the high R² values. The adsorption isotherm results showed the following order of fitting:Freundlich > Halsey >Harkins-Jura > Langmuir.The result of the thermodynamic study showed the sorption process to be spontaneous. Adsorption kinetic data were studied using pseudo-first and pseudo-second order models. The results indicated that the pseudo-second order model gives better interpretation to the adsorption data. The experimental results show that velvet tamarind seed has a significant capacity for removal of lead, iron and copper ions from waste water streams.