Fe- and SiFe-pillared clays from a mineralogical waste as adsorbents of ciprofloxacin from water

Abstract

Considering the problem of the massive use of pharmaceuticals that find their way to the watercourses, pillared clays obtained from mineral clays have a great potential for their application in the removal of these pollutants by adsorption. In this work, Fe and SiFe-pillared clays were obtained from a mineral-industry waste, characterized and their removal capacity for ciprofloxacin (CPX) from aqueous media was evaluated. The Fe- and SiFe-pillared clay precursors were dried by two methods: freeze-drying and stove-drying. The influence of drying method on the structure and adsorptive properties of the pillared materials were studied. The pillared clays characterization showed higher hydrophobicity, sedimentation capacity, and porosity than the raw material. The adsorbed quantity values of CPX were comparable for all materials. The adsorption isotherm fits suggested the presence of heterogeneous adsorption sites for the pillared clays whereas the raw material shows homogeneous adsorption sites. The results showed that the drying method had a greater influence on Fe-PILC than on SiFe-PILC. In particular, the quantity of adsorbed CPX was constant at different pH values for freeze-drying Fe-PILC and the adsorption kinetic was faster than the other adsorbents at basic pH values. The analysis of the CPX-adsorbent adsorption complexes allowed to propose the formation of a mononuclear bidentate complex at pH 10.