Removal of DDT from aqueous solutions using mesoporous silica materials

Background: There are few reports about adsorbents for the effective removal of large-molecule pesticides such as DDT (1,1,1-trichloro-2,2′ bis(p-chlorophenyl)ethane). Some mesoporous silica materials and their modified derivatives might serve as good adsorbents for these large organic molecules because of their large pore diameter and special pore structures. In this work, the adsorption processes of DDT in aqueous solutions were investigated using different mesoporous silica materials, including HMS, MCM-41, SBA-15 and MCM-48. Results: All these materials exhibit efficient DDT removal, and the adsorption is a rapid processwith over 50% of DDT removed within approximately 2 h. The efficiency of DDT removal is influenced by the adsorbent characteristics, such as pore volume, pore diameter, connectivity between pore channels and surface OH groups. The influences of water/acetone ratio and initial DDT concentration in solution were also explored. It was found that with enhancing DDT solubility, the addition of acetone in the reaction solution had no evident impact on DDT adsorption efficiency. Increasing the initial concentration of DDT resulted in a decrease of DDT adsorption efficiency. The adsorption kinetics of DDT on mesoporous silica material is shown to be pseudo-second-order. After thermal treatment at a relatively low temperature of 450 °C, the adsorbed DDT was completely decomposed and the adsorbents, except MCM-41, were regenerated well. Conclusion: The results demonstrate the potential of a simple and efficient new approach for the removal of OCPs (organochlorine pesticides), especially large OCP molecules from surface water or groundwater.