Organo magadiites for diclofenac adsorption: influence of the surfactant chain

The presence of drugs in aquatic environments has been considered a global challenge and several remediation technologies have been proposed, including adsorption. In this study, new diclofenac adsorbents were obtained from the reaction of sodium magadiite (Na-Mag) with surfactants dodecylpyridinium chloride hydrate (C₁₂pyCl) and hexadecylpyridinium chloride monohydrate (C₁₆pyCl)), 1-hexadecyltrimethylammonium bromide (C₁₆Br), and dodecyltrimethylammonium bromide (C₁₂Br). The synthesis was carried out in the microwave at 50 °C for 5 min using surfactant amounts of 100% and 200% in relation to the cation exchange capacity of Na-Mag. The elemental analysis indicated that surfactants with a longer organic chain were more incorporated into Na-Mag, whose values were 1.42 and 1.32 mmol g^-1 for C₁₆pyMag200% and C₁₆Mag200%, respectively. X-ray diffraction results suggested formation of intercalated products with basal space in the range of 2.81-4.00 nm. Diclofenac was quickly adsorbed on all organophilic magadiites, at an equilibrium time of 1 min. Drug capacity adsorption was influenced by the arrangement and packing density of organic cations, the basal distance, and the organic contents of the samples at high drug concentrations. Alkylpyridinium magadiites exhibited maximum adsorption capacities higher than alkylammonium magadiites, of 96.4, 100.7, 131.7, and 166.1 mg g^-1 for C₁₂pyMag100%, C₁₂pyMag200%, C₁₆pyMag100%, and C₁₆pyMag200%, respectively, at pH 6.0 and 30 °C. Diclofenac removal by samples was not affected by the presence of ibuprofen, which was also removed from binary system by organophilic magadiites reaching removal of 76.5% and 86.9% by C₁₆pyMag100% and C₁₆pyMag200%, respectively. Regeneration studies demonstrated a drug removal percentage of 83-92% for C₁₆pyMag and C₁₆Mag after three cycles of adsorption.