Effect of temperature and soil pH on the sorption of ibuprofen in agricultural soil

Abstract

Besides many natural factors, soil pH and temperature can have significant effects on the sorption of pharmaceuticals in soils. This is the first study, which aimed to evaluate the effect of soil pH and temperature on the sorption of ibuprofen in soil. Sorption–desorption experiments at 20°C indicated weak retention of ibuprofen in the soil. Sorption of ibuprofen in the soil was affected by both temperature and pH with the latter showing much greater effect. The extent of ibuprofen sorption increased with decreasing pH mainly due to the change of ibuprofen speciation from negatively charged ions at high pH to the neutral form at low pH. At pH 4, the distribution coefficient K_d was 1.30 l/kg, whereas at pH 8, it was only 0.42 l/kg. When temperature increased, the sorption of ibuprofen decreased, showing that its sorption was exothermic.