Intensify Removal of Nitrobenzene from Aqueous Solution Using Nano-Zero Valent Iron/Granular Activated Carbon Composite as Fenton-Like Catalyst

To obtain a good catalytic effect of removing refractory organics from water by Fenton process, granular activated carbon (GAC) supported nano-zero valent iron (nZVI) composite (nZVI/GAC) was prepared by adsorption-reduction method, and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS). The catalytic degradation activity of the composite was evaluated to remove nitrobenzene (NB) pollutant via a heterogeneous Fenton-like system, and the initial pH value, nZVI/GAC dosage, and H2O2 concentration influencing on NB removal were also investigated at room temperature. Experimental results showed that nZVI particle was uniformly dispersed over GAC matrix, and average particle size was 40-100 nm without agglomeration. The nZVI/GAC composite was very efficient in removing NB with average percentage of more than 85 %. However, the removal rate of Fenton-like reaction was highly affected by pH value, H2O2 concentration, and nZVI/GAC dosage. The optimal reaction conditions were pH 4.0, 40 mg/L NB, 5.0 mmol/L H2O2, and 0.4 g/L nZVI/GAC in this study. Stability and repeatability tests as well as mechanism analysis illustrated that GAC improved catalytic action via enhancing nZVI dispersion and accelerating Fe(III)/Fe(II) cycle attributing to internal iron-carbon microelectrolysis in nZVI/GAC composite. Iron utilization efficiency, which played an important role in NB degradation by Fenton-like greatly increased resulting in dissolved iron < 0.6 mg/L. This phenomenon strongly implied that the nZVI/GAC Fenton-like process was not only a practical combination of adsorption and Fenton oxidation but also some synergetic effects existing in such an nZVI/GAC composite.