REMOVING PROMETRONE FROM WATER BY CLAYS AND ORGANIC CLAYS

The removing power of natural or inorganic clays and organoclays (OCls ) for prometone from water was studied as related to the clay layer ch arge density, organic cation type and organic cation saturation degree of the clay. Two different natural smectites (high charge SAz and low charge SWy) and those treated with two alkylammonium cations (octadec ylammonium and hexadecyltrimethylammonium) were assayed by measuring t he adsorption isotherms and fitting the data to the Freundlich equatio n. The Freundlich parameter Kf, the distribution coefficients Kd(0.3) and, that on organic carbon basis, Koc were calculated and used as rel ative measures of the sorption capacity. The inorganic original smecti tes show low and medium prometrone adsorption (Kf(SAz) = 29 and Kf(SWy ) = 138 mmol/kg) inversely proportional to their layer charge density, although the relative sorption capacity depends on the prometrone con centration level. The OCls generally adsorb more prometrone (Kf from 6 1 to 1031 mmol/kg) than the inorganic samples. The organoclay characte ristics favouring the prometrone sorption are high charge density, qua ternary alkylammonium in the interlayer and organic cation saturation slightly below CEC. However, for low charge smectite primary alkylammo nium and organic cation saturation above CEC promoted herbicide adsorp tion. (C) 1998 Elsevier Science Ltd. All rights reserved.