Sorption and degradation of ranitidine in soil: Leaching potential assessment

Abstract

Pharmaceuticals have been categorized as emerging contaminants that may be hazardous to the environment. To assess their environmental risk, understanding their fate and behaviour is highly needed, particularly in soil where little is known. This study investigated sorption, degradation and mobility potential of ranitidine (RAN) from soil to groundwater in two soils with different physicochemical properties. Sorption resulted in data were found to fit well to isotherm models following the order: linear model > Freundlich > Langmuir with R² of up to 0.98. RAN showed low sorption affinity to soils with maximum adsorption coefficient (K_d) of 21.47 L kg^-1. Physicochemical properties for soil and RAN showed insignificant positive correlation to K_d values except the sand%, which showed significant negative correlation. Degradation of RAN was fitted to the first order exponential decay model with minimum DT50 (time for a 50% dissipation in RAN concentration) values of 31.6 d under non-sterile conditions. Prolonged DT50 of 62.4 d was obtained in soils from sterile treatments indicating the microbial activity role in dissipation of RAN process. To predict potential leaching of RAN in soil, this study experimentally obtained values of K_d, K_oc and DT50 were implemented in mathematical screening models. Results showed different but moderate leaching potential of RAN in soils.

Keywords: Degradation; Leaching potential; Pharmaceuticals; Soil; Sorption.