Effect of sorption process on cadmium transport

The effect of sorption of cadmium to sediments is investigated through an experimental and numerical study. A numerical model is developed to evaluate the kinetic and equilibrium sorption process of heavy metal transport and transformation. The model was calibrated with results from experiments on cadmium and salt injection in a circular flume. The effect of sediment on sorption was then investigated by the aid of advection–dispersion experiments and numerical results. The results show that sorption reduces the dispersion coefficient but has no effect on advection rate. The results also indicate that the linearisation method of estimating sorption parameters is unsuitable. It was also found that a pseudo second-order model for kinetic sorption improves the results obtained in comparison with a first-order model. Comparison between the kinetic and equilibrium models showed that assuming equilibrium conditions underestimates transport velocity.