A novel electro-catalytic membrane contactor for improving the efficiency of ozone on wastewater treatment

A novel electro-catalytic membrane contactor was designed to break the two constrains in O3 wastewater treatment technology simultaneously: the mass transfer of O3-water and the decomposition rate of O3 into OH. In the electro-catalytic membrane contact ozonation (ECMCO) process, O2 and O3, in the gas chamber, diffuse through the hydrophobic membrane into the water phase; O2 is electro-reduced to H2O2 that catalyzes O3 producing OH to degrade organic compounds rapidly. The removal rate of nitrobenzene (NB) was significantly improved by the combination of membrane contactor and electro-catalytic process. The removal rates of NB in 120 min were 85%, 55% and 23% for ECMCO, membrane contact ozonation and electrolysis, respectively. O3 concentration and current density had positive effects on the removal of NB, which was related to the accumulated H2O2 concentration in aqueous phase. Gas flow had slight positive effects on NB removal when it was lower than 50 mL/min. The pH of the feed may affect the production and the form of H2O2 and hence the removal of NB. The highest removal rate in 120 min was up to 95.7% at the initial pH of 4.5. Mass transfer and electrolysis are synthetic in ECMCO process. On one hand, the mass transfer of O3 increased by 2 times due to the electro-catalytic production of H2O2. On the other hand, the existence of O3 promoted the production of H2O2. ECMCO has great potential on promoting mass transfer and decomposition of O3 into OH for the industrial application of O3.