| Research Abstract |
[1] Recovery of ammonia and nitrate ion from ammonium nitrate in waste water by steam distilllation adding lead (II) oxide.
Lead (II) oxide was added to 0.1-2M NH_4NO_3 solutions at 373K to precipitate basic lead (II) nitrates and to recover NH_3 simultaneously by steam distilllation for 0.5-2h. Effects of the molar ratio of PbO/NO_3^- and steam distilllation time on the removal of NO_3^- and recovery of NH_3, and the composition of basic lead (II) nitrate were examined. The removal of NO_3^- as pb(NO_3) _2・ 5pb(OH)_2 and recovery of NH_3 reached ca.100% at the PbO/NO_3^- molar ratio of 4 for 1 h. Above 0.5M NH_4NO_3, the removal of NO_3^- was independent on the initial concentration of NO_3^-. The recovery of NH_3 was analogous to the removal of NO_3^-.
[2] Reduction of sodium nitrate solution by in situ buff abrasion of leadplate
Nitrate ions were reduced by fine Pb powder produced by continuous abrasion of Pb plate with buff abrasive in NaNO_3 solution. Under 25-80ﾟC,initial concentrat
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ion of NO_3^- 0.01-0.1M,and rotation speed of buff 400-800rpm, 20-100% nitrate ion was reduced to NO_3^-, N_2 and/or NH_3 within 12h. Since reduction rate of NO_3^- was extremely slow, maximum percentages of formed N_2 and NH_2 were 14,6, respectively at 12h. Pb was oxidized at 12h to PbO containing unreacted Pb.
In the case of producing bigger Pb particles (20mum) by using coarse buff (#120) and increasing rotation speed, the reduction rate NO_3^- increased due to an increase in amount of abrabed Pb and surface area of Pb by removing PbO layr grown on Pb particles. However, the reduction efficiency of Pb decreased with increasing amount of unreacted Pb core.
[3] Reduction rate of sodium nitrate by lead drops with wet-ballmilling
In a ballmill reactor, metal oxides formed on the lead drops surface by reduction of nitrate ions were continuously removed by contacting with each other.
Under5-80ﾟC,initial concentration of NaNO_3 0.05-0.1M,and ballmill rotation speed, omega, 80-180rpm, NO_3^- was reduced to NO_2^- fast, then slowly to N_2 and NH_3. NO_3^- was reduced to NO_2^- 32-100% in 10h, but the reduction rate of NO_2^- was very low, so the maximum percentages of N_2 and NH_3 from NO_2^- were only 6 and 10%, respectively.
Above 40ﾟC,NO_3^- was reduced under zero-order reaction and NO_2^- was formed corresponding to the reduction stoichiometry. The reduction rate was proportional to omega^<1/2>, and the apparent activation energy was 27.5kJ-mol^<-1>, but independent of the NO_3^- concentration. These results may suggest that the rate determining step is the peeling of PbO layr on the particle surface. Below 25ﾟC,the reduction rate decreased with reaction time as the surface was not covered completely with PbO due to the lowering of the rate. Less
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