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摘要: 針對有色金屬冶煉煙氣中濕法脫汞過程產生的硫脲汞溶液難處置的問題,研究提出了電沉積從硫脲汞溶液中回收汞的新工藝。采用線性電位掃描法得到汞電沉積過程的陰極極化曲線,考察了不同雜質離子對硫脲汞溶液陰極極化曲線的影響。結果顯示,在控制陰極電位為?0.55~?0.45 V的條件下,溶液中的汞可選擇性沉積,溶液中Fe3+、Cu2+和H2SO3并不會影響溶液中汞的電沉積,即汞選擇性電沉積的電位為?0.55~?0.45 V。采用控電位技術對硫脲汞溶液電解回收汞工藝進行研究,探究了電解質種類和濃度、電解液溫度、攪拌速率、電解時間等因素對汞回收效率的影響。得到在陰極材料為銅片的條件下,最佳的電解工藝參數:電解質為0.24 mol·L?1 Na2SO4,電解液溫度為30~40 ℃,攪拌速度為100~300 r·min?1,
$ {\rm{SO}}^{2-}_{3}$ 濃度為8 mmol·L?1,電解時間為5 h。最佳工藝條件下,溶液中汞的回收效率可達98%以上。對陰極電解產物進行分析,陰極上的汞為單質汞,且純度超過99%。Abstract: Mercury, a heavy metal, can seriously harm human bodies and the environment due to its characteristics of high toxicity, biological enrichment, and long-range migration. The non-ferrous metal smelting industry is one of the main sources of atmospheric mercury pollution in China. Therefore, controlling atmospheric mercury emissions from non-ferrous smelting plants is very important. The wet cleaning process has been widely applied in the purification of smelting flue gas because of its advantages such as a high removal efficiency, stable operation, and low cost. During the wet purification process, thiourea is usually added because it can reduce the oxidation potential of mercury and react with mercury to form stable coordination ions, resulting in the high-efficiency removal of mercury from high-sulfur smelting flue gas. However, mercury recovery from scrubbing solutions containing mercury and thiourea obtained from the wet cleaning process is difficult. In this study, a novel technology to recover mercury from the thiourea mercury solution via electrodeposition was proposed and investigated. The linear potential scanning method was applied to obtain the reduction potential of mercury. It was determined that the optimal potential of the mercury electrodeposition process should be controlled between ?0.55 V and ?0.45 V because the presence of ferric ions, copper ions, and sulfite ions did not seriously affect the electrodeposition of mercury. Controlled potential electrolysis was employed to efficiently recover mercury from thiourea mercury solution, and the effects of key parameters, including electrolyte type and concentration, electrolyte temperature, stirring rate, and electrolytic time, on the mercury recovery efficiency were explored. The optimal process conditions are as follows: a cathode material of copper sheet, electrolyte of 0.24 mol·L?1 Na2SO4, electrolyte temperature of 30–40 ℃, stirring speed of 100–300 r·min?1,$ {\rm{SO}}^{2-}_{3} $ concentration of 8 mmol·L?1, and electrolytic time of 5 h. Under the optimal process conditions, the mercury recovery efficiency mercury is over 98%. The electrolytic products on the cathode are elemental mercury, and the corresponding purity is over 99%.-
Key words:
- acid solution /
- thiourea /
- electrodeposition /
- mercury recovery /
- controlled potential
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表 1 模擬洗滌凈化液的主要化學組成(質量濃度)
Table 1. Elemental composition of simulated cleaning solution
mg·L?1 Hg2+ Zn2+ Pd2+ Cu2+ Cd2+ 70 125 10 10 10 Fe2+ F? Cl? As3+ H2SO4 30 200 600 80 500 表 2 石墨電極和銅片電極不同區域能量色散X射線光譜元素分析結果
Table 2. Results of EDX elemental analysis in different areas of graphite cathode and copper cathode
Element Mass fraction (graphite electrode)/% Mass fraction (copper sheet electrode)/% Area 1 Area 2 Area 3 Area 1 Area 2 Na 11.68 10.77 2.49 0 0 Cl 13.11 14.86 4.90 0 0 S 53.07 35.43 14.53 0.54 0.34 Hg 22.15 38.94 78.09 99.46 99.66 259luxu-164 -
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