The Study Of Copper Corrosion Products Catalyzed Reduction Of Ndma With Zero-valent Iron

NDMA is the most representative pollutant of nitrosamine pollutions among the emerging nitrogenous disinfection byproducts.Its potential carcinogenic ability is greatly higher than other disinfection by-products,such as trihalomethane.EPA confirms the mass concentration corresponding to unit carcinogenic risk is 0.7 ng·L-1.It is listed as B2 cancerogenic substance,which can't be eliminated effectively through the conventional treatment process.During the enhanced treatments,the degradation of NDMA with UV has the best effect.However,it needs large energy consumption and rigorous condition.Thus,it is not suitable for practical application.Due to wide availability of raw materials and convenient operation,the reduction technology with zero-valent iron is widely concerned.Zero-valent iron can degrade NDMA through reduction,but it requires long time.As a result,a new method should be developed to improve the reaction rate.Coppere corrosion products(Cu(OH)2,Cu2 O,CuO and Cu2(OH)2CO3)are the corrosion products of domestic water supply copper tubes and can be used as catalysts to enhance the reaction.As a result,it has the great potential to catalyze the reduction of NDMA with zero-valent iron.In the paper,copper corrosion products are applied to catalyze the reduction of NDMA with zero-valent iron.The influences of the loading of copper corrpsion products,pH,dissolved oxygen,and rotate speed on the reaction were investigated.The morphology and combining state of the metal powder which were got after reaction were analyzed.Basing on the above results,the mechanism was proposed.Besides,the results can provide data support for the practical application.The investigation on the influence factors of the copper corrosion products catalyzed reduction of NDMA showed that copper corrosion products could catalyze the reduction of NDMA with zero-valent iron effectively.When the loading of iron powder was 10 g·L-1,the loading of copper corrosion product was 5 mmol·L-1,reaction time was 18 h,the removal rate reacheed 67.8%.CuO showed the the best catalytic effect,the removal rate was 98.8%.The loading of copper corrosion products presented the positive correlation with NDMA removal rate.The rotation speed which was too fast or too low,increased dissolved oxygen and alkaline condition restrained the reduction reaction.Under the weak acid condition,the system which contained Cu2 O got the highest removal rate of NDMA.In the systems which contained the remaining corrosion products,the removal rate will be higher and the reaction speed will be higher with lower pH values.Analysis of organic products for copper corrosion products catalyzed reduction of NDMA with zero-valent iron showed that primary degradation products of NDMA included unsymmetrical dimethylhydrazine(UDMH)and dimethylamine(DMA).Moreover,concentration of UDMH and DMA increased with the degradation of NDMA,showing that the reductive pathway is catalytic hydrogenation.Analysis of morphology and junction state of solid products in reaction process showed that newly formed cuprous oxide existed during the copper corrosion products catalyzed reduction of NDMA with zero-valent iron.In addition,the existence of copper corrosion products enhanced surface activity to some extent by changing surface morphology of zero-valent iron and improved reduction reaction.