Role of acidic post-treatment of activated carbon in aqueous mercury adsorption

Mercury can be largely found in some industrial wastewaters such as chlor-alkaline, paint and battery producing. Mercury removal has attracted great interest due to its dangerous and adverse effects on human health. Activated carbon is one of the best candidates for aqueous mercury removal because of its low cost and excellent adsorptive properties. In the present work, Hg (II) adsorption of a commercial activated carbon with and without Nitric acid treatment was compared in a batch system. For acidic treatment, concentrated acid and activated carbon suspension was left to boil in a simple reflux system for 3h. Iodine adsorption test was carried out to investigate the changes in porous characteristics during acid treatment. The results for iodine adsorption of two samples were similar indicating no change in structural properties during acid treatment. To evaluate the effects of acid treatment on the carbon surface functional groups, FTIR analysis for both types of activated carbon was compared resulting a relatively high oxidation. Kinetic and equilibrium studies were performed considering effective parameters including contact time, initial pH and initial concentration. It can be concluded that Nitric acid treatment of activated carbon has enhanced Hg (II) adsorption capacity due to modification of surface functional groups but has no effect on adsorption kinetic.

Keywords:

Acidic Treatment , Activated Carbon , Adsorption , Mercury , Surface Functional Groups