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

Abstract

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°C and 25°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 0.4 μg kg⁻¹) at both temperatures (15°C and 25°C). Desorption isotherm coefficients at 15°C and 25°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°C (10.88) compared to 15°C, showing a decreasing trend with increasing compound concentration at 15°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.

Keywords:

• Naproxen
• adsorption-desorption
• aquifer material
• hysteresis

Acknowledgments

This work was carried out within the framework of the projects Consolider-Tragua and CGL2010-22168-C03-02, financed by the Ministry of Science and Innovation (Spain). The thorough and constructive reviews of anonymous reviewers have greatly improved the quality of the paper.