Adsorption behavior of toxic tributyltin to clay-rich sediments under various environmental conditions

The adsorption and desorption behavior of tributyltin (TBT) from aqueous solution to clay-rich sediments was studied under various conditions (pH, salinity) using the batch technique. Sediments containing illite, kaolinite, and montmorillonite in different proportions were used as sorbent materials. Several physicochemical parameters of the sediments (e.g., Brunauer-Emmett-Teller [BET] surface area, cation exchange capacity [CEC], total organic carbon [TOC]) were evaluated to assess the influence of sediment characteristics to the adsorption capacity for TBT Adsorption isotherms were linear over the concentration range of 100 to 1,000 ng(Sn)/ml. The adsorption coefficient (Kd) values range from 29 to 70 at the pH value generally found in marine systems (pH 8). The adsorption capacity shows a maximum in the range of pH 6 and 7. Salinity is also an important factor in controlling TBT adsorption. The strongest adsorption was observed at salinity of 0/1000, and it strongly decreases with increasing salinity. The adsorption mechanism is controlled by the properties of the clay minerals as well as the aquatic chemistry of TBT. Desorption takes place over the studied pH range (4-8) when contaminated samples interact with TBT-free water at given experimental conditions.