Effective removal of lanthanum ions from aqueous solution using rice husk: impact of experimental variables

The focus of the present work is to optimize different experimental parameters such as nature of electrolyte, pH, amount of adsorbent, ions concentration, equilibration time, temperature, and operating mode. The effective removal of lanthanum ion (La3+) using biomaterial such as rice husk (RH) was determined by radio-tracer technique. The adsorption phenomenon was verified by FTIR, SEM and EDX techniques. The adsorption data was well fitted to linear and nonlinear forms of Freundlich, Langmuir and Dubinin-Radushkevich isotherm models with characteristic Freundlich constants of n = 2.087 +/- 0.084 and K = 2.81x10(-4) +/- 6.387x10(-6) mol/g and Langmuir constants of Q(m) = (1.046 +/- 0.105)x10(-5) mol/g and K-L = 5347 +/- 995 dm(3)/mol. The sorption free energy was 10.78 +/- 0.641 kJ/mol indicating the chemisorption interaction between the La3+ ions and the RH with pseudo 2nd order kinetics. Thermodynamic parameters were evaluated using Van't Hoff equation with Delta G values indicating spontaneity of the process. A positive Delta H value of 28.563 kJ/mol suggested an endothermic nature of the adsorption. Freundlich adsorption capacity of La3+ ions was 2.81x10(-4) mol/g for RH indicating that it locally available cheaper material is good alternative for costly commercial adsorbents and may be used for waste management of radionuclide's.