Application of superparamagnetic mesoporous silicates on nalidixic acid removal

Abstract

The main objective of this research is to evaluate removal efficiency of nalidixic acid (NAL) residues in synthetic wastewater at high concentration (0-30 mg/L) by adsorption on functionalized superpapramagnetic mesoporous silicates (F-HMS-SP) and to study effect of magnetic field on cake formation of adsorbents removal by ultrafiltration(UF). Five types of surface functional groups (3-aminopropyltrimethoxy-, 3-mercaptopropyltrimethoxy-, n-octyldimethyl-, 4-triethoxysilyl butyronitrile- and phenyltrimethoxy functional group) were grafted on pristine superpapramagnetic mesoporous silicates (HMS-SP) via post-grafting method denoted as A-HMS-SP, M-HMS-SP, OD-HMS-SP, N-HMS-SP and PTM-HMS-SP respectively. NAL adsorption kinetic of all adsorbents were compatible with the pseudo-second order model and implied the intraparticle diffusion as a rate limiting step. Hydrophobic surface of OD-HMS-SP and PTM-HMS-SP provided highest adsorption capacity comparing with hydrophilic adsorbents; however, it was still lower than PAC. Moreover, electrostatic interaction played an important role for NAL adsorption mechanism. Greatly reduction of cake resistance (Rc) was observed due to magnetic system which caused a slow-down of the cake built-up. Moreover, electrostatic interaction between adsorbent and membrane surface was found to affect on Rc value. The presence of NAL adsorbed on F-HMS-SP can affect electrostatic interaction between adsorpbent and UF membrane surface.