Removal of nalidixic acid from aqueous solutions using a cathode containing three-dimensional graphene

Herein three-dimensional graphene (3DG) was synthesized by solution combustion method. A nanostructured 3DG modified carbon paper as the cathode was employed in the homogeneous electro-Fenton method for degradation of nalidixic acid from aqueous solutions and as an anode electrode, graphite was used. The physic-chemical properties of 3DG powder and modified carbon paper were studied by the SEM, XRD, AFM, FTIR, CV and BET analyses. The ability of the resultant 3DG modified carbon paper cathode for hydrogen peroxide production was investigated in solution fed with air. Results showed that the value of hydrogen peroxide that was electrogenerated by using 3DG electrode is 4 times more than bare carbon paper and graphene oxide modified electrode. The consequence of running parameters including current intensity (mA), initial solution pH, initial concentration of nalidixic acid (mg L⁻¹) and process time were investigated comprehensively in a series of batch experiments which were optimized by response surface method (RSM) and the optimized amounts of each parameter were respectively 300 mA, 3.5, 15 mg L⁻¹ and 300 min. The pharmaceutical removal efficiency was 90% under these optimum conditions. The total organic carbon (TOC) measurements showed 87.3% mineralization of 15 mg L⁻¹ drug at 7 h. The gas chromatography (GC) linked to a mass spectrometry (MS) was used to recognize the generated intermediates through the nalidixic acid degradation.