Biosorption of Lead (II) by Natural Bentonite: Adsorbent Characterization and Performance Assessment

In this research, the results of bentonite characterization (pH value of bentonite suspension, point of zero charge, cation exchange capacity, SEM, XRF, DTG) are presented. The results of lead (II) removal efficiency at initial lead (II) concentrations of 200, 300 and 400 mg/L, and biosorbent dosage of 1 gram in 50 ml of lead(II) solution, are also presented, as well as the values of the Freundlich and Langmuir constants from the Freundlich and Langmuir adsorption isotherms. The obtained results showed that removal efficiency is high for all three examined initial lead (II) concentrations, and it is above 99%. The lead (II) removal efficiency slightly decreases with an increase in initial lead concentration. Experimental data obtained from adsorption experiment with contact time of 2.5 minutes, stirring rate 100 rpm, temperature 250C and pH value 5 are better fitted with the linearized Langmuir equation isotherm, giving an R2 value closest to unity (0.9994), than to linearized Freundlich equation (0.9886).