Comparison of Adsorption Models for Cd and Zn in the Berau Delta:Water–Sediment System

Adsorption is important process for controlling metals transfer from dissolved phase to solid phase. Cd and Zn become trace metal which generally used in human activity and the release of those trace metals into aquatic environment cannot be evaded.The purpose of this work was to compare adsorption models of Cd and Zn in water-sediment system in Berau Delta, East Kalimantan. Sediment and water sample were collected at 12 stations. Measuring Cd and Zn concentration, water sample analysis was conducted using organic chemicals (Ammonium Pyrrolidine Dithio Carbamate and Methyl Isobutyl Ketone) and inorganic chemicals (nitric acid) based on back extraction procedure. On the other hand, sediment analysis was conducted using acid destruction according to USEPA method 3050b. The data would be calculated in some different adsorption model: Partition model, Freundlich model and Langmuir model. In this study, Berau Delta was divided into two groups: North river stream (N) and South river stream (S). In both groups,Langmuir isotherm model was the most representative model for adsorption process in water-sediment system. In North stream, the linearity of data gave R^2=0.949 for Cd and R^2=0.838 for Zn, whereas, R^2=0.575 for Cd and R^2=0.944 for Zn calculated in the South stream. Maximum adsorption capacity of Cd was 0.5-0.6 mg.kg^-1 and maximum adsorption capacity of Zn was 12-43 mg. kg^-1. Those maximal adsorption capacities illustrated the total capability of sediment as Cd and Zn deposit. Another Cd and Zn input will not be adsorbed and probably become bioavailable for aquatic life.