Adsorption of linear alkylbenzene sulfonate (LAS) on soils

Experimental measurements of the adsorption of linear alkylbenzene sulfonate (LAS) on soils were made at 25°C using a continuous adsorption apparatus. The adsorption of LAS on natural soils could be divided into two stages: linear and exponentially increasing isotherms. At low LAS concentration (< 90 μg ml−1), the adsorption isotherms were linear and Kd was among 1.2 to 2.0. At high LAS levels (>90 μg ml−1), cooperative adsorption was observed and the adsorption amount of LAS increased exponentially with the increasing of LAS concentration in solution. LAS adsorption mechanisms on soil were mainly specific site surface interactions and hydrogen bonding. The LAS adsorption capacity of a soil significantly depended on its physical clay content. Under real soil environments where LAS levels are rather low, the LAS adsorption ability of a soil is very weak.