Cyanide Removal and Recovery by Electrochemical Crystallization Process
Alkaline chlorination, an efficient but high chemical cost process, is commonly employed for cyanide (CN<sup>−</sup>) removal from CN-rich wastewater streams. CN<sup>−</sup> removal and recovery through the precipitation of Prussian Blue (Fe<sub>4</sub><sup>...
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MDPI AG
2021-09-01
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| Series: | Water |
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| Online Access: | https://www.mdpi.com/2073-4441/13/19/2704 |
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| author | Natacha Martin Vinh Ya Vincenzo Naddeo Kwang-Ho Choo Chi-Wang Li |
| author_facet | Natacha Martin Vinh Ya Vincenzo Naddeo Kwang-Ho Choo Chi-Wang Li |
| author_sort | Natacha Martin |
| collection | DOAJ |
| description | Alkaline chlorination, an efficient but high chemical cost process, is commonly employed for cyanide (CN<sup>−</sup>) removal from CN-rich wastewater streams. CN<sup>−</sup> removal and recovery through the precipitation of Prussian Blue (Fe<sub>4</sub><sup>III</sup>[Fe<sup>II</sup>(CN)<sub>6</sub>]<sub>3</sub>, PB) or Turnbull’s Blue (Fe<sub>3</sub><sup>II</sup>[Fe<sup>III</sup>(CN)<sub>6</sub>]<sub>2</sub>, TB) were realized using iron salts, leading to a cost-effective and sustainable process producing a valuable recovery product. However, the precipitation of PB and TB is highly affected by pH and dissolved oxygen (DO). CN<sup>−</sup> removal and recovery from CN-containing water by crystallization of PB and/or TB were investigated using dissolved iron that was electrochemically generated from a sacrificial iron anode under various pH values, initial CN<sup>−</sup> levels (10 to100 mg/L) and DO levels (aeration, mechanical mixing, and N<sub>2</sub> purging). It was shown that the complexation of CN<sup>−</sup> with Fe ions prevented the vaporization of HCN under acidic pH. At pH of 7 and initial CN<sup>−</sup> concentration of 10 mg/L, CN<sup>−</sup> removal efficiency increases linearly with increasing Fe:CN<sup>−</sup> molar ratios, reaching 80% at the Fe:CN<sup>−</sup> molar ratio of 5. A clear blue precipitate was observed between the pH range of 5–7. CN<sup>−</sup> removal increases with increasing initial CN<sup>−</sup> concentration, resulting in residual CN<sup>−</sup> concentrations of 8, 7.5 and 12 mg/L in the effluent with the Fe:CN<sup>−</sup> molar ratio of 0.8 for initial concentrations of 10, 50 and 100 mg CN<sup>−</sup>/L, respectively. A polishing treatment with H<sub>2</sub>O<sub>2</sub> oxidation was employed to lower the residual CN<sup>−</sup> concentration to meet the discharge limit of <1 mg CN<sup>−</sup>/L. |
| first_indexed | 2024-03-10T06:48:37Z |
| format | Article |
| id | doaj.art-d0eaa9933cd14cbc82498dca4bd618cc |
| institution | Directory Open Access Journal |
| issn | 2073-4441 |
| language | English |
| last_indexed | 2024-03-10T06:48:37Z |
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| spelling | doaj.art-d0eaa9933cd14cbc82498dca4bd618cc2023-11-22T17:01:20ZengMDPI AGWater2073-44412021-09-011319270410.3390/w13192704Cyanide Removal and Recovery by Electrochemical Crystallization ProcessNatacha Martin0Vinh Ya1Vincenzo Naddeo2Kwang-Ho Choo3Chi-Wang Li4Department of Water Resources and Environmental Engineering, Tamkang University, New Taipei City 25137, TaiwanDepartment of Water Resources and Environmental Engineering, Tamkang University, New Taipei City 25137, TaiwanDepartment of Civil Engineering, SEED Sanitary Environmental Engineering Division, University of Salerno, Via Ponte don Melillo 1, 84084 Fisciano, ItalyDepartment of Environmental Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 702-701, KoreaDepartment of Water Resources and Environmental Engineering, Tamkang University, New Taipei City 25137, TaiwanAlkaline chlorination, an efficient but high chemical cost process, is commonly employed for cyanide (CN<sup>−</sup>) removal from CN-rich wastewater streams. CN<sup>−</sup> removal and recovery through the precipitation of Prussian Blue (Fe<sub>4</sub><sup>III</sup>[Fe<sup>II</sup>(CN)<sub>6</sub>]<sub>3</sub>, PB) or Turnbull’s Blue (Fe<sub>3</sub><sup>II</sup>[Fe<sup>III</sup>(CN)<sub>6</sub>]<sub>2</sub>, TB) were realized using iron salts, leading to a cost-effective and sustainable process producing a valuable recovery product. However, the precipitation of PB and TB is highly affected by pH and dissolved oxygen (DO). CN<sup>−</sup> removal and recovery from CN-containing water by crystallization of PB and/or TB were investigated using dissolved iron that was electrochemically generated from a sacrificial iron anode under various pH values, initial CN<sup>−</sup> levels (10 to100 mg/L) and DO levels (aeration, mechanical mixing, and N<sub>2</sub> purging). It was shown that the complexation of CN<sup>−</sup> with Fe ions prevented the vaporization of HCN under acidic pH. At pH of 7 and initial CN<sup>−</sup> concentration of 10 mg/L, CN<sup>−</sup> removal efficiency increases linearly with increasing Fe:CN<sup>−</sup> molar ratios, reaching 80% at the Fe:CN<sup>−</sup> molar ratio of 5. A clear blue precipitate was observed between the pH range of 5–7. CN<sup>−</sup> removal increases with increasing initial CN<sup>−</sup> concentration, resulting in residual CN<sup>−</sup> concentrations of 8, 7.5 and 12 mg/L in the effluent with the Fe:CN<sup>−</sup> molar ratio of 0.8 for initial concentrations of 10, 50 and 100 mg CN<sup>−</sup>/L, respectively. A polishing treatment with H<sub>2</sub>O<sub>2</sub> oxidation was employed to lower the residual CN<sup>−</sup> concentration to meet the discharge limit of <1 mg CN<sup>−</sup>/L.https://www.mdpi.com/2073-4441/13/19/2704cyanide removalcrystallizationprussian blueiron hexacyanoferrate |
| spellingShingle | Natacha Martin Vinh Ya Vincenzo Naddeo Kwang-Ho Choo Chi-Wang Li Cyanide Removal and Recovery by Electrochemical Crystallization Process Water cyanide removal crystallization prussian blue iron hexacyanoferrate |
| title | Cyanide Removal and Recovery by Electrochemical Crystallization Process |
| title_full | Cyanide Removal and Recovery by Electrochemical Crystallization Process |
| title_fullStr | Cyanide Removal and Recovery by Electrochemical Crystallization Process |
| title_full_unstemmed | Cyanide Removal and Recovery by Electrochemical Crystallization Process |
| title_short | Cyanide Removal and Recovery by Electrochemical Crystallization Process |
| title_sort | cyanide removal and recovery by electrochemical crystallization process |
| topic | cyanide removal crystallization prussian blue iron hexacyanoferrate |
| url | https://www.mdpi.com/2073-4441/13/19/2704 |
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