Norfloxacin adsorption on montmorillonite and carbon/montmorillonite hybrids: pH effects on the adsorption mechanism, and column assays

Abstract

The presence of norfloxacin antibiotic (NFX) in drinking water raises significant scientific concern due to the health and environmental problems that may cause. This study aimed to evaluate the NFX removal: 1) in batch adsorption at different pH values on montmorillonite (M) and montmorillonite-carbon hybrids (M-HC); 2) in continuous columns experiments, to assess the technological application of these hybrids as domestic filters, using one M-HC as adsorbent material ranging from 1% to 5%. Batch experiments showed that adsorption occurred in all the samples, being M the material with the highest adsorption capacity (95% of adsorption for cationic NFX). For the M-HC the adsorption seemed to be not strongly dependent of the pH (20%- 41% of adsorption). The characterization of adsorbents and NFX adsorption products (FTIR, XRD, and zeta potential analysis) disclosed that adsorption occurs at both the external surface and the interlayer space of M. For the M-HC synthesized without activation, the interlayer space seemed to be predominantly responsible; while for the activated M-HC the adsorption occurred at the external surface (its interlayer was destroyed). The column experiments revealed that the best adsorption capacity and highest flow were attained using 1% of adsorbent material in the column packing.