Modification of clays and zeolites by ionic liquids for the uptake of chloramphenicol from water

- Ionic liquids (ILs) were used to modify selected Earth materials of high cation exchange capacities.
- Modified materials resulted in significant uptake of chloramphenicol (CP), an antibiotic.
- CP uptake was affected by the surface configuration of ILs and the fractional organic carbon content.
- Partitioning mechanism contributed significantly to CP uptake.
- This research extended new application of ILs for wastewater treatment.

Chloramphenicol (CP) is frequently detected in wastewaters even after treatment. In this study, the interactions between CP and selected Earth materials modified by an ionic liquid (IL) were investigated. Changes in surface hydrophobicity of the materials after modification were demonstrated in contact angle measurements and zeta potential determination. The sorption sites of IL on zeolite and illite were limited to the external surfaces, while interlayer sorption sites of IL in montmorillonite (MMT) played a major role in addition to surface sorption. The different sites for IL modification resulted in different sites for CP sorption. CP uptake was limited to the external sites for IL-modified zeolite and illite, while both external and interlayer sites were available for CP uptake on modified MMT. The dual sorption sites for CP by modified MMT resulted in a much larger CP distribution coefficient (Kd). The adsorption of CP on the modified materials followed a linear sorption isotherm and the Kd increased as the IL loading on the Earth materials increased. In addition, good correlation was found between the fractional organic carbon content (foc) of the modified materials and the Kd values. These results all pointed to a partitioning mechanism for the uptake of CP on IL-modified Earth materials.

Uptake of CP on Earth materials modified by IL was attributed to surface anion exchange and hydrophobic interaction. However, the CP distribution coefficient was highly correlated to the factional organic carbon content, suggesting that partitioning played a major role for CP removal from water.135