Comparison of VUV/H2O2 and VUV/PMS (peroxymonosulfate) for the degradation of unsymmetrical dimethylhydrazine in water

In the present research, VUV/H2O2 and VUV/PMS processes as alternative technologies for the degradation and mineralization of unsymmetrical dimethylhydrazine (UDMH) were evaluated and compared for the first time. The result indicated that the degradation efficiency in VUV-based system was higher than that in UVC-based system. Addition of peroxide in VUV system significantly improved the degradation efficiency. Both VUV/H2O2 and VUV/PMS were able to completely remove 100 mg.L-1 of UDMH within 25min. Compared with VUV/H2O2, VUV/PMS exhibited a stronger mineralization ability and superior tolerance to a wide initial pH range, different UDMH concentrations, and various types of inorganic anions. After 30 min of reaction, the total organic carbon (TOC) concentration decreased by 31.8 % and 81.8 % in VUV/H2O2 and VUV/PMS, respectively. The results indicated that VUV/PMS were efficient in removing and mineralizing UDMH in water. It was also determined that center dot OH was the dominant reactive species in the degradation and mineralization of UDMH in VUV/H2O2 process. However, direct oxidation with PMS and deep oxidation with reactive species were responsible for UDMH degradation and mineralization, respectively, in VUV/PMS process. This study provides effective technical support for the treatment of wastewater from rocket launch.