The effect of sediment motion on adsorption of cadmium

This paper describes the results of experimental work in a circular flume and a reactor device to show the role and importance of flow velocity, sediment movement type and concentration in the kinetic adsorption and transport of cadmium in both bed and suspended load conditions. The results show that the rate of adsorption is directly connected with sediment motion type and flow velocity. Considering a specific sediment concentration for the bed load condition, it was observed that the equilibrium capacity increased by 20% as the flow velocity changed from 0·35 to 0·7 m/s. Moreover, the use of batch reactors overestimates sorption capacity. However, for suspended load conditions, the equilibrium capacity was not significantly affected by the flow velocity or sediment motion type (comparing flume and batch reactor results). It was experimentally deduced that increasing the sediment concentration load by 300% would decrease the equilibrium cadmium adsorption in unit mass by 170% and 250% for bed and suspended loads respectively.