Naproxen Adsorption-Desorption in a Sandy Aquifer Matrix: Characterisation of Hysteretic Behavior at Two Different Temperature Values

Adsorption/desorption processes (sorption isotherms) of Naproxen in a sandy aquifer matrix sediment were investigated using batch tests to compare Naproxen sorption behavior at 15 degrees C and 25 degrees C. Both temperatures are representative of the aquifer media and environmental conditions. Adsorption was well described by linear isotherms with low sorption affinity to aquifer material (K-d of 0.4g kg(1)) at both temperatures (15 degrees C and 25 degrees C). Desorption isotherm coefficients at 15 degrees C and 25 degrees C were 5.0 and 4.9, respectively. Naproxen hysteresis indices were between 9.98 and 10.8, indicating that a Naproxen fraction may be irreversibly fixed in the aquifer media, being higher at 25 degrees C (10.88) compared to 15 degrees C, showing a decreasing trend with increasing compound concentration at 15 degrees C. The low sorption of Naproxen leads to potential leaching to groundwater if present in irrigation water, and its prevalence in an aquifer media when directly injected in wells for groundwater recharge.