Solar photocatalytic mineralization of antibiotics using magnetically separable NiFe2O4 supported onto graphene sand composite and bentonite

Adsorbent supported photocatalysis is developing as a potential waste water treatment technology. In this work, NiFe2O4 was supported onto graphene sand composite (GSC) and bentonite (BT) supported to prepare magnetic NiFe2O4/GSC and NiFe2O4/BT nanocomposties. Graphene sand composite (GSC) was prepared by graphitization of sugar over river sand. The size of NiFe2O4/BT and NiFe2O4/GSC was found to be 50 and 60 nm respectively. Mesoporous nature of prepared photocatalysts was confirmed by BET adsorption/desorption experiments. NiFe2O4/GSC and NiFe2O4/BT exhibited ferromagnetic behaviour and could be separated from treated water using external magnetic field. The band gaps of NiFe2O4/GSC and NiFe2O4/BT were found to be 2.41 and 2.42 eV, respectively. The adsorption and photocatalytic activity of NiFe2O4/GSC and NiFe2O4/BT was tested for the mineralization of ampicillin (AMP) and oxytetracycline (OTC) antibiotics under solar light. The adsorption process had significant effect on the mineralization of AMP and OTC. Simultaneous adsorption and degradation (A + P) process were the most efficient for antibiotic degradation. The complete mineralization of antibiotics was obtained using NiFe2O4/GSC/A+P and NiFe2O4/BT/A+P catalytic processes. The kinetics of mineralization were explored using power law model. Magnetically recoverable NiFe2O4/GSC and NiFe2O4/BT are recyclable and displayed significant recycle efficiency and quick recovery for 10 consecutive catalytic cycles. (C) 2016 Elsevier Ltd. All rights reserved.