Unraveling influence of metal species on norfloxacin removal by mesoporous metallic silicon adsorbent

Metal-modified adsorbent had appreciable adsorption capacity and fast rate toward norfloxacin (NOR), but limited studies focused on the influence of metal species on adsorbents' performance. In this study, Fe and Cu were chosen to be loaded on mesoporous silicon SBA-15 for absorbing NOR and investigating the key function of metal species. An obvious synergy effect was found between active species and supporter. A high adsorption capacity (44.8 mg g(-1) for Fe/SBA-15 and 78.3 mg g(-1) for Cu/SBA-15) and short equilibration time (< 2 h) were obtained. NOR adsorptions on two processes were described well by pseudo-second-order kinetics, particle diffusion equation, and Langmuir isotherm. The adsorption processes were spontaneous, but NOR adsorption on Cu/SBA-15 was endothermic while its adsorption on Fe/SBA-15 was exothermic. HA had dual effect on the adsorption efficiency, with a promotion at low HA concentration but an inhibition at high concentration. NOR removal increased first and then decreased with pH ascension from 3 to 9 for both Fe/SBA-15 and Cu/SBA-15, achieving maximum at pH = 7. Comparative characterizations and experiments suggested that NOR adsorption processes were dominated by electrostatic interactions, n-pi EDA interactions, hydrogen bonds, and surface complex. The greater n-pi EDA and complex efficiency of Cu with NOR resulted in the superior performance of Cu/SBA-15.