Adsorption of some herbicides onto organo-clays from aqueous solution

ABSTRACT Clay samples were compared with modified clay samples for the sorption of 1,1'- dimethyl - 4, 4' bipyridillium dichloride (paraquat, cationic herbicide) from water by measuring the adsorption isotherms and fitting the data to Langmuir and Freundlich equation. Bentonite, illite and sepiolite were chosen as clay samples and DB, NB, DI, NI, DS and NS as organo-clays. Specific surface area, pore size distribution and monolayer volume values of the samples were determined at 77 K with B.E.T method showing a decrease in the order of natural samples dodecylammonium and nonylammonium clays respectively. X-Ray powder diffraction analysis of the samples and the effects of modifying agents on the layer structure of clays were also investigated. After modification, an increase in dooi values was observed except sepiolite. Organic matter contents of modified samples were determined as the percentage of H, C, N. Cm (adsorption capacity) ranged from 0.382 mmol/g for DS up to 2.229 mmol/g for NI. Kdo,3 (distribution coefficient) values increase from 0.177 for DS up to 0.843 for NI. The organic carbon partition coefficients ( Koc) and Kf values were also calculated and the highest values were found for NI. The batch experiment indicates that illite and nonylammonium illite (NI) are the most effective adsorbents among the clay samples and modified clay samples respectively. Although paraquat herbicide is a cationic herbicide, modification of illite and bentonite with nonylammonium ion increased the adsorption capacities of the samples in the order being DS < S < NS < DB < B < DI< NB < I< NI. In this study, it was proved that paraquat can be removed from aqueous solution by using organo-modified clays especially nonylammonium illite and bentonite instead of natural clays. Nonylammonium illite can also be used as an effective oral adsorbent in the case of paraquat poisoning. Keywords : paraquat, adsorption, clay, organo-clay, removal