Mobility of cadmium in granitic soil using batch and mini column tests

This paper highlights the physico-chemical properties of granitic residual soils and the effectiveness of using batch and column tests to study the migration and sorption of heavy metal (Cadmium) through compacted soil layer. Granitic residual soil was taken from Broga, Selangor and this material has undergone physical-chemical tests conducted based on British Standard Method, BS1377 (1990). For sorption analysis, batch and mini column infiltration tests were conducted according to USEPA (1992) and Antoniadis et al. (2007) methods, respectively. For batch test, results showed that Kd values for both single and mixture solutions were fitted to Linear equations (R 2> 0.8). For Langmuir Isotherm, only mixture solution (KL=0.0015 L/g; R 2= 0.9353) was fitted to the isotherm while for Freundlich Isotherm, only single solution (KF=0.0137 L/g; R 2= 0.9266) was fitted to the isotherm. The curve of adsorbed heavy metal concentration, qe versus equilibrium concentration, Ce showed that the sorption of Cd was increased with the equilibrium concentration, until at one point the sorption was decreased. The adsorption capacity, qe and distribution coefficient, Kd of single solution (maximum adsorption, qe= 1.10 mg/g; Kd=0.0062 L/g) were higher compared to mix solution (maximum adsorption, qe= 0.12 mg/g; Kd=0.0022 L/g). For mini column infiltration test, different G-force (ranged from 230-g to 1440-g) and different types of solutions (single and mixture solutions) were studied in this research. The breakthrough curves showed the concentration of Cd has become higher with the increasing of G-force. The sorption capacity in single and mixture solutions could be ranked as 230-g>520-g>920-g>1440-g. The increasing of G-force also reduced the Kd values. The Kd values for single solution were also higher compared to mixture solution due to zero competition for adsorption of metals thus, Kd values increased. The comparison between batch and column infiltration has also been studied in order to know the better sorption analysis. In both single and mixture solutions, Kd in batch test showed higher values (single solution, Kd= 6.2 L/kg and mixture solution, Kd= 2.2 L/kg) compared to all Kd values in column infiltration test. Results demonstrated that mobility and sorption of Cd were highly depended on physical and chemical properties of the soil. Study also showed that both sorption test have different effects on mobility of heavy metals through soils. The column infiltration test gave the exact values of qe and Kd compared to the batch test since the condition of columns method applied were similar to the natural soil conditions.