Catalyst for the degradation of 1,1-dimethylhydrazine and its by-product N-nitrosodimethylamine in propellant wastewater
A three-component metal catalyst was prepared and used in the process of catalytic wet peroxide oxidation (CWPO) for the degradation of unsymmetrical dimethylhydrazine (UDMH) in propellant wastewater with H2O2. It was structurally characterized using scanning electron spectroscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX), and its catalytic activity was evaluated using indexes such as the efficiency of UDMH degradation and chemical oxygen demand (COD) removal and the concentrations of ammonia (NH3–N), formaldehyde (HCHO), total nitrogen (TN), total organic carbon (TOC) and N-nitrosodimethylamine (NDMA). Besides, the reaction system was monitored using UV-Vis full wavelength scanning spectroscopy and liquid chromatography-mass spectroscopy (LC-MS). As a result, it was observed that the degradation mechanism involved ˙OH attacking the amino group and homocoupling in UDMH with the simultaneous transformation of the active component CuII/I. Based on investigation of the reaction factors (H2O2 dosage, temperature, catalyst dosage, pH and initial concentration of UDMH) focusing on the removal of NDMA, the optimal conditions for CWPO with a three-component metal catalyst were determined. The high treatable concentration of UDMH (500 mg L−1), rapid rate and good reusability with a high efficiency of UDMH degradation and COD removal (99.9% in 10 min and 94.6% in 30 min, respectively) and the low concentration of NDMA are merits of the present catalyst.