Environmental Sciences Research Laboratory, Department of Botany, Wilson College, Mumbai.

Department of Chemistry, Bhavan’s Hazarimal Somani college of Arts and Science, Mumbai.

 In the present study, the competitive biosorption properties of nonliving biosorbent, Terminalia catappa L. leaves as a cost effective biosorbent for Pb(II) ions was investigated using batch technique. FTIR analysis of the biosorbent revealed that hydroxyl, carbonyl and carboxyl groups which are involved in the uptake of lead (II) ions. SEM represents porous structure with large surface area. The effects of operational factors including solution pH, biosorbent dose, initial lead (II) ions concentration, contact time and temperature on the biosorption efficiency were studied. The optimum solution pH for Pb(II) ions adsorption by biosorbent was 6.0 with the optimal removal 82.06%. The biosorbent dose 5 mg/mL was enough for optimal removal of 79.35%. The biosorption process was relatively fast and equilibrium was achieved after 90 minutes of contact time. The experimental equilibrium biosorption data were fitted by four widely used two-parameters Langmuir, Freundlich,Dubinin-Kaganer-Redushkevich (DKR) and Temkin isotherm equations. Langmuir isotherm model provided a better fit with the experimental data than Freundlich, Temkin and Dubinin-Kaganer-Redushkevich (DKR) adsorption isotherm models by high correlation coefficient value (R²= 0.997). The maximum adsorption capacity determined from Langmuir isotherm was found to be 50.00 mg/g of biosorbent. Simple kinetic models such as pseudo-first-order, pseudo-second-order, Elovich equation and Weber and Morris intraparticle diffusion rate mixing equation were employed to determine the adsorption mechanism. Results indicates that pseudo-second-order kinetic model (R²= 0.999) was found to be correlate the experimental data strongest than other three kinetic models and this suggests that chemical biosorption process was more dominant. Thermodynamic study revealed that the biosorption process was spontaneous, endothermic and increasing randomness of the solid solution interfaces. Tarminalia catappa L. leaves were successfully used for the competitive biosorption studies of Pb(II) ions from aqueous solutions and can be applied in waste water technology for remediation of heavy metal contamination.

Keywords:Adsorption kinetics, Competitive biosorption, Lead (II) ions, Terminalia catappa L., Thermodynamic study.