Investigation of cadmium adsorption potential by suspended sediments of the Rozeh-Chay River, Urmia region at different ionic strengths

In this research, suspended sediments of the Roze-Chay River, which were located on west part of Urmia Lake, were used to investigate the influence of ionic strength on sorption of cadmium. Adsorption of cadmium on the suspended sediments was investigated using batch experiments. The studied sediments (40 g l-1) was equilibrated in 6, 12, and 25 mmol l-1 ionic strength at definite pH with different cadmium concentrations (0-350 µmol l-1). The results indicate the more ionic strength; the less cadmium sorption occurs in all the samples. This effect of ionic strength on sorption can be attributed to the increased competition between competitive ions (Ca2+) and Cd2+. Isotherm data were described by using Freundlich, Langmuir, and Van-Huay models and better fitting were introduced Freundlich and Langmuir models. The average maximum adsorption capacity (b) of cadmium onto the suspended sediments was obtained 15.3 µmol g-1. Therefore, the suspended sediments have a very low potential for the sorption and transfer of cadmium. That means, even if cadmium is present in the bed of the river, these suspended sediments have no significant ability to sorb cadmium ions and cannot be considered as a carrier of cadmium in the environment.