Enhanced removal of diclofenac by an organohalloysite intercalated via a novel route: Performance and mechanism

Abstract

Listen

Translate article

An organohalloysite was prepared using a new procedure. Halloysite (H) was pre-intercalated with dimethyl sulfoxide and then mixed with a solution of hexadecyltrimethylammonium (HDTMA) having a concentration equivalent to six times the CEC of the starting Algerian halloysite. The novel nanohybrid obtained (HH6-d) was characterized and compared with a sample intercalated from the beginning by HDTMA (HH6). Intercalation of HDTMA cations in the interlayer space was evidenced by XRD with an expansion of the basal distance from 7.6 to 26.0 Å for an intercalation rate of 75% (HH6-d) versus 42% for HH6. All materials were used to remove diclofenac (DFC). pH influence, isotherm, thermodynamic data, reusability of the best adsorbent and the mechanism of interaction have been examined. The experimental isotherms were appropriately adjusted by the Redlich-Peterson equation. The best adsorbent adsorbs 154.3 mg g−1, with an adsorption sequence as follows: HH6-d > HH6 > unmodified clay, i.e. according to the intercalated fraction, so that the HDTMA intercalating agent interacts with the diclofenac molecules. This interaction was entropically driven, endothermic and spontaneous. It would involve not only hydrophobic bond between the tail group of HDTMA represented by the hydrocarbon chain and the hydrophobic moiety of DFC represented by the aromatic groups, but also an electrostatic interaction between the negative charge of the carboxylate ion (COO−) and the positive charge of the aluminol groups coating the lumen.