In this work, wet oxidative decomposition of (NH
4)
2SO
4 in an air and Ar atmosphere was conducted in a lab-scale airtight glass vessel reactor by adding Na
2S
2O
8 and H
2O
2 as oxidative agents to (NH
4)
2SO
4 solution. The initial concentration of NH
4+ in (NH
4)
2SO
4 aqueous solution was set to 1,000 mg-NH
4+/dm
3. The experiments were conducted at temperatures of 343–363 K, keeping the initial pH at a prescribed value between 5.5 and 13.5. The mixing molar ratio of (NH
4)
2SO
4/oxidant was set to 1/1 – 1/10.
Results show that the decomposition of (NH
4)
2SO
4 by Na
2S
2O
8 in an alkaline region was more significant than that by H
2O
2 because most H
2O
2 disappeared by self-decomposition under the present conditions. Results further showed that (NH
4)
2SO
4 was almost decomposed completely in about 150 min reaction time by adding Na
2S
2O
8 at a molar ratio of (NH
4)
2SO
4/Na
2S
2O
8=1/3 at 363 K in an alkaline condition of pH=13.5. The rates of decomposition of Na
2S
2O
8 and (NH
4)
2SO
4 were expressed by the first-order kinetics with respect to the concentrations of Na
2S
2O
8 and (NH
4)
2SO
4 with constant initial concentrations of (NH
4)
2SO
4 and Na
2S
2O
8, respectively.
When Na
2S
2O
8 was added to (NH
4)
2SO
4 solution, NH
3(aq) was decomposed by reactive oxygen species such as • SO
4−, • OH
−, • O
−, • O
3−, etc. in an alkaline condition, producing the main reaction product of N
2 and small amounts of NO
2− and NO
3− by-products. In this oxidative decomposition of (NH
4)
2SO
4, O
2 formation was suppressed by the consumption of these reactive oxygen species.
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