Efficient Removal of Ammonia Nitrogen by an Electrochemical Process for Spent Caustic Wastewater Treatment
Spent caustic wastewater produced in a soda plant has a high concentration of ammonia nitrogen (NH<sub>4</sub><sup>+</sup>-N). As excessive NH<sub>4</sub><sup>+</sup>-N discharging into water bodies would cause eutrophication as well as destruction to...
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MDPI AG
2022-11-01
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| author | Sijin Zuo Yinqiao Zhang Ruixin Guo Jianqiu Chen |
| author_facet | Sijin Zuo Yinqiao Zhang Ruixin Guo Jianqiu Chen |
| author_sort | Sijin Zuo |
| collection | DOAJ |
| description | Spent caustic wastewater produced in a soda plant has a high concentration of ammonia nitrogen (NH<sub>4</sub><sup>+</sup>-N). As excessive NH<sub>4</sub><sup>+</sup>-N discharging into water bodies would cause eutrophication as well as destruction to the ecology balance, developing an efficient technology for NH<sub>4</sub><sup>+</sup>-N removal from the spent caustic wastewater is imperative in the current society. In this study, an electrochemical process with graphene electrodes was designed for the NH<sub>4</sub><sup>+</sup>-N removal in the spent caustic wastewater. The removal efficiency of the NH<sub>4</sub><sup>+</sup>-N during the electrochemical process could reach 98.7% at 4 A in a short treatment time (within 120 s) with an acceptable energy consumption (6.1 kWh/m<sup>3</sup>-order). NO<sub>3</sub><sup>−</sup> and NO<sub>2</sub><sup>−</sup> were not detected during the electrochemical process. An insignificant amount of NH<sub>2</sub>Cl, NHCl<sub>2</sub>, and NCl<sub>3</sub> produced in the treatment suggested that little of the NH<sub>4</sub><sup>+</sup>-N reacted with chlorine, that is, chlorination played a negligible role in the NH<sub>4</sub><sup>+</sup>-N removal. By electron equilibrium and nitrogen conversion analysis, we think that NH<sub>4</sub><sup>+</sup>-N was primarily converted to NH<sub>2</sub>(ads) on the surface of a graphene electrode by one-electron transfer during the direct oxidation of the electrochemical process. Due to the high calcium ion (Ca<sup>2+</sup>) in the spent caustic wastewater, the electrode scale significantly increased to 1.4 g after treatment of 240 s at 4 A. By X-ray diffraction (XRD) analysis, the composition of the electrode scale is portlandite Ca(OH)<sub>2</sub>. Although the electrode scale was obvious during the electrochemical treatment, it could be alleviated by alternating the electrode polarity. As a result, the life and efficiency of the graphene electrode for NH<sub>4</sub><sup>+</sup>-N removal could remain stable for a long time. These results suggest that the electrochemical process with a graphene electrode may provide a competitive technology for NH<sub>4</sub><sup>+</sup>-N removal in spent caustic wastewater treatment. |
| first_indexed | 2024-03-09T19:12:38Z |
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| language | English |
| last_indexed | 2024-03-09T19:12:38Z |
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| spelling | doaj.art-d6c47a4b8b244465a8cb35e208f6a07f2023-11-24T04:06:06ZengMDPI AGCatalysts2073-43442022-11-011211135710.3390/catal12111357Efficient Removal of Ammonia Nitrogen by an Electrochemical Process for Spent Caustic Wastewater TreatmentSijin Zuo0Yinqiao Zhang1Ruixin Guo2Jianqiu Chen3School of Engineering, China Pharmaceutical University, Nanjing 211198, ChinaSchool of Engineering, China Pharmaceutical University, Nanjing 211198, ChinaSchool of Engineering, China Pharmaceutical University, Nanjing 211198, ChinaSchool of Engineering, China Pharmaceutical University, Nanjing 211198, ChinaSpent caustic wastewater produced in a soda plant has a high concentration of ammonia nitrogen (NH<sub>4</sub><sup>+</sup>-N). As excessive NH<sub>4</sub><sup>+</sup>-N discharging into water bodies would cause eutrophication as well as destruction to the ecology balance, developing an efficient technology for NH<sub>4</sub><sup>+</sup>-N removal from the spent caustic wastewater is imperative in the current society. In this study, an electrochemical process with graphene electrodes was designed for the NH<sub>4</sub><sup>+</sup>-N removal in the spent caustic wastewater. The removal efficiency of the NH<sub>4</sub><sup>+</sup>-N during the electrochemical process could reach 98.7% at 4 A in a short treatment time (within 120 s) with an acceptable energy consumption (6.1 kWh/m<sup>3</sup>-order). NO<sub>3</sub><sup>−</sup> and NO<sub>2</sub><sup>−</sup> were not detected during the electrochemical process. An insignificant amount of NH<sub>2</sub>Cl, NHCl<sub>2</sub>, and NCl<sub>3</sub> produced in the treatment suggested that little of the NH<sub>4</sub><sup>+</sup>-N reacted with chlorine, that is, chlorination played a negligible role in the NH<sub>4</sub><sup>+</sup>-N removal. By electron equilibrium and nitrogen conversion analysis, we think that NH<sub>4</sub><sup>+</sup>-N was primarily converted to NH<sub>2</sub>(ads) on the surface of a graphene electrode by one-electron transfer during the direct oxidation of the electrochemical process. Due to the high calcium ion (Ca<sup>2+</sup>) in the spent caustic wastewater, the electrode scale significantly increased to 1.4 g after treatment of 240 s at 4 A. By X-ray diffraction (XRD) analysis, the composition of the electrode scale is portlandite Ca(OH)<sub>2</sub>. Although the electrode scale was obvious during the electrochemical treatment, it could be alleviated by alternating the electrode polarity. As a result, the life and efficiency of the graphene electrode for NH<sub>4</sub><sup>+</sup>-N removal could remain stable for a long time. These results suggest that the electrochemical process with a graphene electrode may provide a competitive technology for NH<sub>4</sub><sup>+</sup>-N removal in spent caustic wastewater treatment.https://www.mdpi.com/2073-4344/12/11/1357ammonia nitrogenelectrochemistryspent causticgraphene electrodeelectrode scale |
| spellingShingle | Sijin Zuo Yinqiao Zhang Ruixin Guo Jianqiu Chen Efficient Removal of Ammonia Nitrogen by an Electrochemical Process for Spent Caustic Wastewater Treatment Catalysts ammonia nitrogen electrochemistry spent caustic graphene electrode electrode scale |
| title | Efficient Removal of Ammonia Nitrogen by an Electrochemical Process for Spent Caustic Wastewater Treatment |
| title_full | Efficient Removal of Ammonia Nitrogen by an Electrochemical Process for Spent Caustic Wastewater Treatment |
| title_fullStr | Efficient Removal of Ammonia Nitrogen by an Electrochemical Process for Spent Caustic Wastewater Treatment |
| title_full_unstemmed | Efficient Removal of Ammonia Nitrogen by an Electrochemical Process for Spent Caustic Wastewater Treatment |
| title_short | Efficient Removal of Ammonia Nitrogen by an Electrochemical Process for Spent Caustic Wastewater Treatment |
| title_sort | efficient removal of ammonia nitrogen by an electrochemical process for spent caustic wastewater treatment |
| topic | ammonia nitrogen electrochemistry spent caustic graphene electrode electrode scale |
| url | https://www.mdpi.com/2073-4344/12/11/1357 |
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