CARBENDAZIM ADSORPTION ON MONTMORILLONITE, PEAT AND SOILS

The adsorption of carbendazim by peat and montmorillonite was studied as a function of the exchangeable cations and temperature. The adsorpt ion on soils was also studied. The kinetics of carbendazim adsorption on peat showed that adsorption equilibrium was reached within 1 h. The order of adsorption of carbendazim on peat was as follows: H+-peat > Cu2+-peat > Co2+-peat > Mg2+-peat > K+-peat, and the thermodynamic par ameters appeared to suggest an adsorption mechanism involving hydrogen bonds, although in the H+, Cu2+ and Co2+ samples a protonation proces s and adsorption of the protonated species were also likely. The kinet ics of carbendazim adsorption on montmorillonite (mont.) showed that e quilibrium was reached within 1 h. The order of adsorption was: H+-mon t. > Cu2+-mont. > Co2+-mont. > Ca2+-mont., the adsorption on the H+ an d Cu2+ samples being much greater than that on the other samples. For the H+ and Cu2+ samples, the thermodynamic parameters appeared to sugg est a double mechanism: physical adsorption, and protonation and adsor ption by ion exchange. The most probable mechanism for the adsorption of carbendazim on the Co2+ and Ca2+ samples was physical bonding. The capacity for adsorption of this fungicide on soil was dependent on the organic matter, nitrogen and clay content, as well as on the cation e xchange capacity. No significant correlation was found with pH, C/N ra tio or free iron content.