Adsorption, kinetics and thermodynamic studies of Lead (II) ions from aqueous solutions onto bio-adsorbent prepared from locust bean seed shell

Adsorption has been widely used for the removal of heavy metals from waste water due to its availability, efficiency, profitability and its low cost of operation. In this study, locust bean seed shell powder prepared from locust been seed shell (LBSS) was used as adsorbent. Batch adsorption experiments were carried out in order to study the effect of process variables such as; adsorbent dosage, time, concentration, and temperature. The adsorbents both unmodified and modified were characterized using SEM, XRF, and FTIR. The results showed structural modification of the modified locust bean seed shell powder (MLBSSP). The adsorption equilibrium data of MLBSSP perfectly conform to Freundlich adsorption model based on its high correlation coefficient which is close to unity (0.9738). However, the kinetic studies showed that the process fit in well into pseudo second order due to its higher R2 (0.9662) in MLBSSP. The positive values obtained for change in enthalpy indicate that the adsorption process is endothermic in nature while the negative values obtained for change in entropy of the process reveal decrease in the randomness of the process and the positive values of change in Gibb’s free energy suggest non spontaneity of the adsorption process. The adsorbent (MLBSSP) shows excellent performance in removing Pb (II) ions from aqueous solutions and can be used as a substitute to the available expensive adsorbents since it is cheap, non-toxic and abundantly available.