Chemical Engineering Journal, Vol.330, 1128-1136, 2017
Organokaolin for the uptake of pharmaceuticals diclofenac and chloramphenicol from water
Organoclays were used as landfill liners, with added value of its enhanced uptake and retention of hydrophobic organic compounds. In addition, uptake of inorganic anions on organoclays was attributed to the electrostatic interactions between the negatively charged anions and the positively charged surfactant admicelle or bilayer formation on the surface of clays. In this study, interactions between anionic drug diclofenac (DC) and neutral chloramphenicol (CP) and organokaolin (OK) were investigated to seek further expansion of using organoclays to present seepage and leaching of waters containing emerging compounds such as pharmaceuticals. Different preparations of OK had drastic effect on the performance of drug uptake on OK. Under the surfactant bilayer surface coverage, the uptake of DC was fast and followed the Langmuir sorption isotherm. The amount of DC adsorbed far exceeded the anion exchange capacity of the OK, suggesting other interactions besides electrostatic interactions played an important role. On the contrary, the uptake of CP followed a linear sorption isotherm. Zeta potential determination confirmed changes of surface charges, while contact angle measurements showed progressive increases in hydrophobicity as the surfactant loading level increases. Instrumental analyses indicated that the drug uptake was limited to the external surfaces of OK and the sorption of DC involve in the -C=O functional group. Molecular simulation revealed possible interactions via the amine group for DC sorption. The mechanistic study confirmed the validity of using OK for the uptake of DC and CP from water or leachate, a superior feature pertaining to surfactant modification.