Catalytic wet oxidation of high concentration formaldehyde wastewater over Pt/nitrogen-doped activated carbon

High concentration formaldehyde (HCHO) wastewater was treated by catalytic wet oxidation (CWO) using Pt/activated carbons. The activated carbons (ACs) with different surface nitrogen content were prepared by H2O2 pre-oxidation and thermal treatment with melamine. The corresponding Pt/ACs were prepared by excess volume impregnation process and characterized by N-2 adsorption/desorption, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The CWO experiments were performed in a co-current upflow fixed bed reactor at 125 degrees C and 1.0MPa. The results revealed the positive effect of nitrogen-containing surface groups on the Pt-AC interactions, and resulting in a smaller Pt nanoparticles size and a narrower distribution. Compared with the original Pt/AC, more nitrogen content of Pt/AC showed higher catalytic activity in the mineralization of high concentration formaldehyde (17,000mg/L) and COD (23,000mg/L). After 170h of time on stream, HCHO and COD concentrations of effluent from Pt/AC increased from 482 to 805mg/L, and from 1895 to 2980mg/L, respectively, while those from Pt/nitrogen-doped AC just increased from 0.6 to 30.6mg/L, and from 48 to 345mg/L even at 350h of time on stream. Lesser Pt leaching and the extent of agglomeration of Pt NPs were observed over nitrogen-containing Pt/AC. CWO using Pt/nitrogen-doped AC may be applied as a promising treatment for high concentration HCHO wastewater prior to biological system.