CADMIUM ADSORPTION AT DIFFERENT PORE-WATER VELOCITIES

Batch and column experiments were conducted to study the effect of por e water velocity on the adsorption of cadmium (Cd) onto a homogeneous nonaggregated porous medium under controlled environmental conditions. A wide range (5-214 cm/hr) of pore water velocities was imposed to ob serve adsorption effects. The results of batch experiments showed that adsorption coefficients are affected by the solid-to-liquid ratio, th e adsorption coefficient increasing with this ratio. The batch-determi ned adsorption isotherm constants differed from those determined from column experiments. There was no evidence of nonequilibrium processes occurring in the flow-through system. For most of the column breakthro ugh curves, the linear equilibrium model adequately described the data , The fits of this model to the observed breakthrough data indicated t hat the adsorption coefficient remains fairly constant with velocity. However, flow-determined adsorption coefficients were clearly higher t han batch-determined ones at the same solid-to-liquid ratio.