Photo-reduction of nitrate to nitrite in aqueous solution in presence of CaO: Selectivity, mechanism and application

Liu, Ting; Deng, Jinhua; Yang, Congling; Liu, Meizhi; Liu, Yong

doi:10.1016/j.seppur.2022.122364

Cited by 7 publications

(10 citation statements)

References 55 publications

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“…The concentration of NO 3 – during the reaction was also determined, but little to no generation of NO 3 – was observed in the UV/PS/CaO process (data not shown). A possible explanation is that CaO promoted the photolysis of generated NO 3 – to form NO 2 – , which was proven by our previous work Figure b shows that the concentration of N 2 H 4 in the UV/PS/CaO process first increased to 0.1 mg N/L and then decreased to 0.03 mg N/L in UV/PS/CaO, suggesting that N 2 H 4 acted as an intermediate during the NH 4 + -N oxidation. , As 17.0% of N 2 H 4 could be directly removed by PS (Figure c), the oxidation of N 2 H 4 by PS would also exist in the UV/PS/CaO process.…”

Section: Resultsmentioning

confidence: 97%

“…Unless otherwise mentioned, chemicals were of at least analytical grade and used without further purification. CaO was calcined at 400 °C for 4 h in a muffle furnace before use . Stock solutions of NH 4 + -N were prepared with distilled water (CMP-TA-20L, Youyue Technology Co., Ltd., Chengdu, China).…”

Section: Methodsmentioning

confidence: 99%

“…CaO was calcined at 400 °C for 4 h in a muffle furnace before use. 26 Stock solutions of NH 4 + -N were prepared with distilled water (CMP-TA-20L, Youyue Technology Co., Ltd., Chengdu, China).…”

Section: Methodsmentioning

confidence: 99%

“…CaO is an appealing and cheap solid base with the advantage of environmental friendliness, which can create a favorable alkaline environment for the oxidation of NH 4 + -N. 25 Previous studies concerning flue gas denitrification showed that CaO was enriched with alkali sites and defectivities, 26,27 2− (eq 9, K sp = 9.1 × 10 −6 ), decreasing the amount of SO 4…”

Section: Introductionmentioning

confidence: 99%

“…It has been reported that hydrazine (N 2 H 4 ) and nitrogen oxides (NO x ) could be generated during NH 4 + -N oxidation . N 2 H 4 can be oxidized to nitrogen gas (N 2 ) by PS, − and the generated NO x would also react with the remaining NH 3 to form N 2 . , Moreover, CaO can catalyze the photolysis of nitrate (NO 3 – ) to produce more reactive nitrite (NO 2 – ), which would promote the conversion between oxidation products of NH 4 + -N . Therefore, it is of interest to reveal the evolution of the N species during NH 4 + -N oxidation in the UV/PS/CaO process, which might be critical for understanding the selectivity of oxidating NH 4 + -N to N 2 .…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Rapid Oxidation of Ammonia Nitrogen to Nitrogen Gas by UV-Activated Persulfate with Calcium Oxide

Jiang,

Wang,

Zhou

et al. 2024

ACS EST Eng.

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Advanced oxidation processes (AOPs) for removing ammonia nitrogen (NH 4 + -N) are of increasing interest in wastewater treatment. In this paper, the UV-activated persulfate (PS) process with CaO was applied to oxidize NH 4 + -N to nitrogen gas (N 2 ). Nearly all of the NH 4 + -N (30 mg N/L) could be removed within 15 min, and the N 2 selectivity was achieved at 95.0%. The addition of CaO made NH 4 + -N exist in the form of NH 3 , and HO • was the critical reactive species for NH 4 + -N oxidation. NO, N 2 H 4 , and NO 2 − were identified as oxidation intermediates and could be further removed. The reaction between N 2 H 4 and NO 2 − with the assistance of UV/ CaO promoted N 2 generation during NH 4 + -N oxidation. The increased dosages of CaO (0.2 to 4.0 g/L) and PS (0.6 to 2.4 g/L) could enhance the NH 4 + -N oxidation, while the presence of CO 3 2− (100 mM) significantly retarded the removal of NH 4 + -N. As high removal of NH 4 + -N (100%) and high N 2 selectivity (>79.5%) could be achieved in lake water and secondary wastewater, the proposed UV/PS/CaO process could be potentially applied for the oxidation of NH 4 + -N in practical water treatment.

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