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 charge 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 (octadecylammonium and hexadecyltrimethylammonium) were assayed by measuring the adsorption isotherms and fitting the data to the Freundlich equation. The Freundlich parameter Kf, the distribution coefficients Kd(0.3) and, that on organic carbon basis, Koc were calculated and used as relative measures of the sorption capacity. The inorganic original smectites 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 concentration level. The OCls generally adsorb more prometrone (Kf from 61 to 1031 mmol/kg) than the inorganic samples. The organoclay characteristics favouring the prometrone sorption are high charge density, quaternary alkylammonium in the interlayer and organic cation saturation slightly below CEC. However, for low charge smectite primary alkylammonium and organic cation saturation above CEC promoted herbicide adsorption. (C) 1998 Elsevier Science Ltd. All rights reserved.