ENVIRONMENTAL APPLICATION OF NATURAL BENTONITE AS ADSORPENT OF MERCURY ION FROM AQUEOUS SOLUTION

The adsorption of mercury (Hg (II)) ions onto Natural bentonite was investigated. The effects of pH, initial adsorbent dosage, contact time and temperature were studied in batch experiments. The highest removal ratio (90%) obtained at reaction time of 50 min and pH 5 with the appropriate dosage of adsorbent was 1.5 g/100 mL. In addition to that, pseudo- first and second order kinetic model and Weber–Morris model were applied to describe the adsorption kinetics. The values of correlation coefficient (R2) were 0.83, 0.96 and 0.95, respectively. Which means that the adsorption of Hg (II) ion from aqueous solution onto Natural bentonite was followed the pseudo 2nd order kinetic, and the adsorption process was spontaneous. Langmuir and Freundlich models described the sorption isotherms. The results indicated The Langmuir model gave a better fit (R2= 0.99) than the Freundlich model (R2= 0.95) which mean that the Freundlich and Langmuir model were able to describe properly the isotherm of a mercury ion on bentonite. The thermodynamic parameters indicated spontaneous and endothermic nature of the adsorption process. The results demonstrate that the natural bentonite is effective in the removal of heavy metals from aqueous solutions and can be used as alternative of high cost commercial adsorbents.