Intercalation of sulfonamides in montmorillonite by molecular dynamics and DFT calculations for bioavailability control

Abstract

The intensive use of antibiotics and especially sulfonamides in the livestock industry is getting an alarming level. The presence of these drugs in wastewaters, rivers and underground waters is increasing considerably in developing countries. The molecular interactions of these drugs with the surfaces of clay minerals can be interesting for evaluating their mobility in soils and for preparing composite complexes for optimal use. In this work, the intercalation of antibiotics derivatives of sulfonamides, such as sulfamethazine, sulfamethoxazole, sulfachloropyridazine and sulfacetamide, into the interlayer space of montmorillonite (MNT) is studied at molecular and 3-D periodical crystal structure level by using computational modeling, molecular dynamics and calculations based Density Functional Theory (DFT). Most of these intercalations are energetically favourable, where the role of water molecules is critical. In general, the bioavailability of these compounds by intercalation in MNT is bigger than from the crystalline powder. Spectroscopic properties of these systems showed interesting frequency shifts in the bands of the IR spectrum produced during the intercalation in the confined space of MNT. These results predict that the IR spectroscopy as an interesting analytical technique for monitoring the intercalation of drugs in clay minerals.