Carbendazim adsorption on montmorillonite, peat and soils

SUMMARY The adsorption of carbendazim by peat and montmorillonite was studied as a function of the exchangeable cations and temperature. The adsorption 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 > Cu 2+ ‐peat > Co 2+ ‐peat > Mg 2+ ‐peat > K + ‐peat, and the thermodynamic parameters appeared to suggest an adsorption mechanism involving hydrogen bonds, although in the H + , Cu 2+ and Co 2+ samples a protonation process and adsorption of the protonated species were also likely. The kinetics of carbendazim adsorption on montmorillonite (mont.) showed that equilibrium was reached within 1 h. The order of adsorption was: H + ‐mont. > Cu 2+ ‐mont. > Co 2+ ‐mont. > Ca 2+ ‐mont., the adsorption on the H + and Cu 2+ samples being much greater than that on the other samples. For the H + and Cu 2+ samples, the thermodynamic parameters appeared to suggest a double mechanism: physical adsorption, and protonation and adsorption by ion exchange. The most probable mechanism for the adsorption of carbendazim on the Co 2+ and Ca 2+ 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 exchange capacity. No significant correlation was found with pH, C/N ratio or free iron content.