Effect of a typical anticonvulsant drug carbamazepine on the aggregation of zinc oxide nanoparticles and an insight into their co-transport in porous media

The emergence of new contaminants like engineered nanoparticles (NPs), pharmaceuticals (PhACs), etc., causes a detrimental effect on the ecosystem and the study needs to be done to understand its behavior in the natural environment. In the present study aggregation and transport behavior of zinc oxide nanoparticles (nZnO) was evaluated in the presence of one of the PhACs, carbamazepine (CBZ). At first, a series of batch experiments were performed with 50 mg/L of nZnO and 1 mg/L of CBZ at different pH (6 and 8) and electrolyte concentration (EC: 1 mmol/L and 20 mmol/L), to study the change in the hydrodynamic diameter of nZnO. The result indicates that the extent of aggregation of nZnO increases with an increase in EC from 1 mmol/L to 20 mmol/L of NaCl or CaCl₂. However, in the presence of CBZ, shows greater colloidal stability at lower EC, and its effect was found to be nominal at higher EC. The transport behavior of nZnO and CBZ was assessed by column experiment, it was found that more than 97 % of nZnO and 99 % of CBZ are retained in the porous media during the injection for different test conditions. Moreover, during transport experiments of longer duration, less than 10 % of nZnO and about 72 µg/L of CBZ were released in the effluent. Therefore, the risk of the release of nZnO is reduced in the presence of CBZ.