Evaluation of bicarbonate impregnated coconut oilcake residue carbon for the removal of mercury II nickel II and cadmium II from aqueous system

Abstract

The adsorption techniques have been widely used for the removal of heavy metals. In this connection, coconut oilcake residue was treated with sulphuric acid in the weight ratio 1:1 and the carbonized material was modified by soaking in 2% sodium bicarbonate solution. The carbon obtained (BCORC) was compared with commercial activated carbon (CAC) procured from market in the removal of heavy metals. Batch experiments were conducted with BCORC and CAC to find out the optimum equilibration time, pH and carbon dosage for the removal of mercury (II), nickel (II) and cadmium (II) from aqueous solutions. In order to understand the sorption capacity of adsorbents, studies were carried out with varying initial concentration of mercury (II), nickel (II) and cadmium (II) ions. Column studies were carried out using 2.5 cm diameter glass column using BCORC and CAC with an initial metal ion concentration of 200 mg L-1.The break point was set as 0.1 mg per 100 mL for these metal ion solutions. Column regeneration studies were carried out up to 5 cycles of operations where as in case of CAC it was found to show no adsorption even after first cycle of operation. Kinetic studies were conducted with BCORC and CAC with various initial concentration of mercury (II), nickel (II) and cadmium (II) solution with carbon dosage of 100 mg/100 ml. It could be seen from the present investigation that the bicarbonate impregnated coconut oilcake residue carbon (BCORC) exhibited a good mechanical strength and abrasion resistance in column studies. The overall adsorption capacity of the BCORC was found to be higher than that of CAC and exhibited considerable removal capacity of these metal ions when they are present in wastewater. Hence it could be concluded that bicarbonate impregnated sulphonated coconut oilcake residue carbon (BCORC) could be considered as an alternative adsorbent for the removal of these toxic metal ion from the water and wastewater. newline newline newline