Amoxicillin separation from aqueous solution by negatively charged silica composite membrane

Silica composite membranes were successfully prepared by acid/ base-catalyzed sol-gel method and characterized by SEM, FTIR, AFM and contact angle Low isoelectric point of the silica layers provided negatively charged composite membranes, resulting electrostatic repulsion forces between membrane surface and amoxicillin molecules at higher pHs. The rejection rate of amoxicillin was studied systematically at different pHs, solute concentrations, transmembrane pressures and temperatures. It was found that acid-catalyzed membrane has higher amoxicillin rejection ratio compared to base-catalyzed membrane. Especially, acid-catalyzed membrane achieved the highest rejection of 90% at the transmembrane pressure of 6 bar, 45 °C, pH = 10, and initial feed concentration of 50 ppm. Long term stability exhibit that the membrane performance in permeation flux was steady for up to 100 h. However, the AMX rejection of 89% was maintained for over 250 h in acid-catalyzed membrane. It was concluded that the use of negatively charged ceramic membranes is promising for removal of amoxicillin from water resources.