Diclofenac Removal\nby Alkylammonium Clay Minerals\nPrepared over Microwave Heating

Diclofenac is an emerging contaminant widely detected\nin water\nand has had adverse effects on the biota. In this study, the adsorbents\nwere prepared by reacting tetradecyl-(C<sub>14</sub>), hexadecyl-(C<sub>16</sub>), and octadecyltrimethylammonium (C<sub>18</sub>) bromides\nwith sodium vermiculite (Na-Ver) and used for the removal of the first\ntime for diclofenac sodium from aqueous solution. Synthesis was carried\nout in a microwave-assisted reactor operating at 50 °C for 5\nmin, using proportions of organic salts in 100 and 200% of the phyllosilicate\ncation exchange capacity. The stability of loaded alkylammonium solids\nwas evaluated under drug adsorption conditions. Adsorption was mainly\ninfluenced by the amount of surfactant incorporated into the clay\nmineral according to the thermogravimetric and CHN elemental analysis\ndata. Samples prepared with 200% CEC presented lower stability at\npH 6.0 and 8.0. Drug adsorption was more effective for C<sub>14</sub>-Ver-200%, C<sub>16</sub>-Ver-200%, and C<sub>18</sub>-Ver-200% samples,\nwith a maximum retention of 97.8, 110.1, and 108.0 mg g<sup>–1</sup>, respectively. The adsorptive capacities of C<sub>14</sub>-Ver-200%,\nC<sub>16</sub>-Ver-200%, C<sub>18</sub>-Ver-200%, C<sub>14</sub>-Ver-100%,\nC<sub>16</sub>-Ver-100%, and C<sub>18</sub>-Ver-100% were reduced\nto 29.0, 36.8, 41.0, 61.0, 50.4, and 58.0%, respectively, compared\nwith their initial value after three adsorption cycles. X-ray diffraction\n(XRD) patterns revealed that diclofenac was adsorbed into the interlayer\nregion of organovermiculites. Fourier transform infrared spectroscopy\n(FTIR), Zeta potential results, and the pH study of adsorption indicated\nthat van der Waals interactions are dominant in the adsorption mechanism.