51. Effect of precursor type on the reduction of concentrated nitrate using zero-valent copper and sodium borohydride.
- Author
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Belay TA, Lin CY, Hsiao HM, Chang MF, and Liu JC
- Subjects
- Hydrolysis, Models, Theoretical, Nitrites analysis, Nitrogen Oxides analysis, Oxidation-Reduction, Particle Size, Surface Properties, Borohydrides chemistry, Copper chemistry, Nitrates analysis, Water Pollutants, Chemical analysis, Water Purification methods
- Abstract
In this study, we demonstrated that the choice of precursor has a strong effect on the reduction of nitrate (NO
3 - ) using zero-valent copper (Cu0 ) synthesized by sodium borohydride (NaBH4 ). Different precursors: CuSO4 , CuO, Cu2 O, Cu powder, and Cu mesh were used to reduce NO3 - at 677 mg-N/L under the reducing conditions of NaBH4 . Compared with the prehydrolyzed samples, those prepared without prehydrolysis exhibited lower reduction rates, longer times and higher concentrations of nitrite (NO2 - ) intermediate. It was found that one-time addition of NaBH4 resulted in higher reduction rate and less NO2 - intermediate than two-step addition. Results showed that Cu0 from CuSO4 possessed the smallest particle size (890.9 nm), highest surface area (26.0 m2 /g), and highest reaction rate (0.166 min-1 ). Values of pseudo-first-order constant (kobs ) were in the order: CuSO4 > CuO > Cu2 O > Cu powder >Cu mesh. However, values of surface area-normalized reaction rate (kSA ) were approximately equal. It was proposed that NO3 - was reduced to NO2 - on Cu0 , and then converted to NH4 + and N2 , respectively; H2 generated from both NaBH4 hydration and Cu (II) reduction contributed to NO3 - reduction as well.- Published
- 2018
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