Study On The Initial Characteristics Of Organic Pollutants And Clay Minerals

Soil contamination caused by organic pollutants has increasingly attracted attention. The residual age and accumulation of organic pollutants in soils are closely related to the formation of organic-mineral complexes. Some experiment results showed that the binding degree of different organic molecules and different inorganic minerals was somewhat different. To study the binding mechanism between them, therefore, is very helpful for understanding and illuminating the residue, transformation, and translocation of organic pollutants in soils. In this experiment 9 organic compounds (including drugs and common organic) with different molecular structures and 2 clay minerals (2:1 type and 1:1 type) were selected and used to build the organic-inorganic complexes. The research about the binding mechanism of organic matters and clay minerals has been carried out and related to molecular structure, charge characteristics and interaction force. The main results obtained are as follows:(1) The permanent charge and variable charge of kaolinite used in the test were+16cmol kg-1 and+12.54 cmol kg-1, and for montmorillonite they were -68 cmol kg-1 and-15.10cmol kg-1, respectively.(2) There were less differences in the surface negative charge demand between organic matters, while the relatively large differences in the surface positive charge demand between organic matters were observed. Of them, protein, cellulose, chitin, chitosan, carbamazepine, gemfibrozil and BHC showed greater surface positive charge demands, while the glyphosate and glucose indicated relatively small surface positive charge demands.(3) Protein, Cellulose, Chitin, Chitosan, Carbamazepine, Gemfibrozil and BHC could be combined with montmorillonite and kaolinite to form organic-mineral complexes, while glucose and glyphosate were difficult to be absorbed by minerals.(4) For organic pollutants, carbamazepine. gemfibrozil and BHCs could be adsorbed onto the surface of montmorillonite with the help of hydrophobic bond to form organic-montmorillonite complexes, and adsorbed onto the surface of kaolinite with both the electrostatic attraction and the hydrophobic bond to form organic-kaolinite complexes. Due to its large water-soluble and less negative charge, glyphosate was difficult to be adsorbed on the surfaces of montmorillonite and kaolinite by the electrostatic attraction.(5) Protein, cellulose, chitin. chitosan could be combined with montmorillonite by means of hydrophobic bond, with kaolinite by both hydrophobic bond and electrostatic attraction, while glucose couldn’t do that due to its larger electrostatic repulsion against the montmorillonite and its strong water solubility.(6) The combination of organic matters and minerals mainly occurred at the surfaces and edges of minerals, all organic matters used in the test failed to enter the interlayers of both montmorillonite and kaolinite.