Arsenate and Arsenite reactions with soil mineral particles

Arsenic, an toxic and hazardous element, is found mainly as arsenate and arsenite in natural systems. There are some evidences addressing as polluted land in soils of Northwestern Meshgin Shahr. In this study examined adsorption(0, 1, 2/5, 10, 15) and desorption(2/5, 10 ,15ppm) of arsenate and arsenite with soil mineral particles. The desorption tests done in three time: 1,hours, 50hours and 39hours. Adsorption models(Langmuir, freundlich, langmuire-freundlich and two surface Langmuir) were applied to describe adsorption data. Results showed that As(V and III) adsorption on soil mineral particles increased by increasing initial concentrations. The rate of adsorption decreased at high initial As concentrations. Also rate of adsorption in clay particles is higher than silt and sand particles. And adsorption of arsenite is more than arsenate in all of samples. But desorption of arsenate is more than arsenite, as in last times(45 and 93hr) arsenite not realesed. Modeling adsorption data showed that two surface Langmuir model can describe adsorption data well based on higher R1 and lower SSE values. Modelling also showed that least squared option described adsorption data well in comparision to linear form of Langmuir and freundlich models. Keywords: Arsenic, adsorption isotherms, Langmuir equation, desorption