萃取法提取铬(Ⅲ)分离铁(Ⅱ)的研究

Selective separation of chromium(Ⅲ) and iron(Ⅱ) by extraction

  • 摘要: 采用皂化的P204+磺化煤油体系共萃铬、铁,选择性反萃分离铬、铁工艺,从电镀污泥硫酸浸出液中回收富集铬.考察皂化率、P204浓度、料液初始pH值、萃取时间、温度、相比等因素对于萃取效果的影响,考察反萃剂组成、浓度、相比等因素对反萃效果的影响.结果表明:P204皂化率及浓度是影响铬的萃取率重要因素.在萃取有机相组成为30 %P204+70 %磺化煤油,皂化率为70 %,料液pH=2.42,VO/VA=1/1,萃取温度28 ℃,振荡时间5 min条件下,经6级逆流萃取达到平衡之后,出口水相铬浓度为0.9 mg/L左右,铬萃取率为99.99 %.采用2段反萃工序有效的分离铬铁:采用2 mol/L硫酸反萃,相比VO/VA=5/1,温度32 ℃,振荡时间5 min,经过3级逆流反萃,铬反萃率为97.5 %,铬浓度富集到29.5 g/L,铁浓度为10 mg/L;反萃铬后负载有机相再用氢氧化钠溶液反萃铁.

     

    Abstract: Chromium (Ⅲ) and iron (Ⅱ) were extracted together by saponified P204 + sulfonated kerosene system, and were selectively stripped to recover chromium from sulfuric acid leaching solutions of electroplating sludge. The effects of the factors were studied, such as saponification rate, P204 concentration, initial pH value, extraction time, temperature and extraction phase ratio on the extraction efficiency, as well as the effects of such factors as the composition, concentration and the ratio of the stripping agent on the stripping efficiency. The results show that the extraction rate of chromium is predominated by the saponification rate and concentration of P204. Under the following optimum conditions: Using 30 %P204+70 %sulfonated kerosene as the extractant, saponification rate is 70 %, pH value of 2.42, VO/VA=1/1, in 28 ℃ and reaction time is 5min, the chromium concentration in the outlet water phase was about 0.9 mg/L and the extraction rate of chromium was 99.99 %by six-stage countercurrent extraction. Effective separation of chromium and iron by two stripping processes: The loaded organic can be stripping using 2mol/L H2SO4, VO/VA=5/1, the temperature is 32 ℃ and reaction time is 5min, stripping rate of chromium was 97.5 %, concentration of chromium enriched to 29.5 g/L and concentration of iron close to 10 mg/L by three-stages countercurrent stripping with 2 mol/L sulfuric acid. After chromium stripping, iron in the loaded organic can be stripped using sodium hydroxide solution.

     

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