Controlling bromate formation in the Co(II)/peroxymonosulfate process by ammonia, chlorine-ammonia and ammonia-chlorine pretreatment strategies
| Autor: | Jingyun Fang, Zhaobing Li, Chii Shang, Li Ling |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Environmental Engineering
Sulfate radicals chemistry.chemical_element Protonation 02 engineering and technology 010501 environmental sciences 01 natural sciences Water Purification Ammonia chemistry.chemical_compound Reaction rate constant Bromide Chlorine Waste Management and Disposal 0105 earth and related environmental sciences Water Science and Technology Civil and Structural Engineering Chemistry Bromates Ecological Modeling Chloramines Cobalt 021001 nanoscience & nanotechnology Bromate Pollution Peroxides Degradation (geology) 0210 nano-technology Oxidation-Reduction Water Pollutants Chemical Nuclear chemistry |
| Zdroj: | Water research. 139 |
| ISSN: | 1879-2448 |
| Popis: | The Co(II)/peroxymonosulfate (Co(II)/PMS) process, producing sulfate radicals (SO4•-), effectively removes organic pollutants in water, while producing a significant amount of bromate (BrO3−) in the presence of bromide (Br−). This paper investigates the ammonia (NH3) addition, chlorine-ammonia (Cl2-NH3) and ammonia-chlorine (NH3-Cl2) pretreatment strategies in controlling BrO3− formation in 20 min in the Co(II)/PMS process at pH 4.0. The addition of NH3 retarded the BrO3− formation, but only at a reduction level of about 9.5% for NH3 concentration of 50 μM, and was mainly attributed to the protonation of NH3 at pH 4 (99.99% as NH4+, did not react with HOBr). Both the Cl2-NH3 and NH3-Cl2 pretreatment strategies at HOCl and NH3 dosages of 15 and 50 μM, respectively, reduced 95% or more of the overall BrO3− formation and retarded the BrO3− formation, with the NH3-Cl2 pretreatment strategy outperforming Cl2-NH3. The reduction of the BrO3− formation was mainly attributed to the formation of monochloramine (NH2Cl) in both pretreatment strategies. NH2Cl effectively outcompetes SO4•- to react with HOBr and forms NHBrCl, with the apparent reaction rate constant between NH2Cl and HOBr more than 100 times faster than that between SO4•- and HOBr. However, the oxidation/degradation of NHBrCl in the Co(II)/PMS process reforms HOBr, and, although less in quantity, is oxidized to BrO3− at higher Co(II) and Br− concentrations. Thus, the NH3-Cl2 and Cl2-NH3 pretreatment strategies inhibit the BrO3− formation more significantly at lower Co(II) and Br− concentrations. In all cases, the generation of SO4•- in 20 min was not affected by the implementation of the three BrO3− pretreatment strategies. |
| Databáze: | OpenAIRE |
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