Carbendazim Transport and Interactions with Regenerated Cellulose Membranes Probed by Analytical Diafiltration

Carbendazim (CBDZ) is widely used for the prevention and control of fungal diseases in agricultural crops. Its extensive and recurrent application may lead to the occurrence of residues in agricultural environments and increase the potential for contamination of aquatic systems. In this study, analytical diafiltration was used to investigate the transport and interfacial association of CBDZ with regenerated cellulose membranes (CELms) rather than to evaluate size-exclusion-based pesticide removal. Continuous diafiltration experiments using the washing mode were performed with an 8.0 ppm CBDZ solution and 10 kDa of CELm at different pH values (3.0–9.0), while permeate flow rate and CBDZ concentration in successive permeate fractions were monitored throughout the process. CBDZ membrane retention (Rm) ranged from (7.4 ± 3.3%) at pH 9.0 to (23.2 ± 2.0%) at pH 3.0, with a maximum membrane-associated amount (\(R_m^{max}\) ) of 478 μg CBDZ per g of CELm. The pH dependence of Rm was accurately described by Rm = 24.9740 + 0.1814 ph − 0.2375 ph2 for 3.0 ≤ pH ≤ 9.0 (r2 = 0.999). The results are consistent with adsorption-mediated interfacial association, mainly involving physicochemical interactions with hydroxyl- and carboxyl-containing functionalities of CELms, while electrostatic interactions contributed less than 3.0% within the pH range of 6.0–7.0. The diafiltration profiles were successfully described by the ExDM–IDZ model. The parameters governing the shape of the retention profile were Rm, associated with the horizontal asymptote, and (j), which describes the decay rate and was related to the evolution of CBDZ concentration and its apparent residence behavior during diafiltration. Overall, these results demonstrate that analytical diafiltration provides a useful framework for investigating the transport, partitioning, and adsorption-mediated interactions of low-molecular-weight, water-soluble pesticides with membrane materials.