用磷酸三丁酯萃取分离硫酸铵母液中的HCN

研究了磷酸三丁酯(TBP)-磺化煤油体系从重庆某企业甘氨酸生产副产物硫酸铵母液中萃取分离HCN的工艺,考察了萃取体系、TBP体积分数、母液初始pH值、相比(Vorg∶Vaq)对萃取HCN的影响以及氢氧化钠浓度、相比(Vaq∶Vorg)和平衡pH值对HCN反萃的影响。结果表明:选用TBP作为萃取剂能够对硫酸铵母液中的HCN进行快速有效的萃取;TBP体积分数、母液初始pH值及相比对HCN萃取率影响显著;以含体积分数35%TBP的有机相作萃取剂,在相比(Vorg∶Vaq)为2∶1的条件下,pH值为2.92的含氰1.71 g/L的硫酸铵母液经3级错流萃取,萃余液中含氰低于0.5 mg/L,氰的萃取率接近100%;在相比(Vaq∶Vorg)为1∶1条件下,以0.6 mol/L的氢氧化钠为反萃液,控制反萃液平衡pH值大于13.0,氰的单级反萃率大于96%;含氰0.78 g/L的有机相在相比为1∶1条件下,经过2级错流反萃,氰基本上被反萃完全,贫有机相不经过处理可循环使用。

Extraction of HCN from ammonium sulfate solutions by using tributyl phosphate solution

The liquid-liquid extraction of HCN from by-product ammonium sulfate solutions generated in the production process of glycine was investigated by using tributyl phosphate(TBP) solution in sulfonated kerosene.The effects of extraction systems,TBP volume fraction,initial pH of mother liquor and volume ratio of organic phase to aqueous phase(Vorg∶ Vaq) on the extraction of HCN,as well as the effects of sodium hydroxide concentration,volume ratio of aqueous phase to organic phase(Vaq∶ Vorg),and equilibrium pH on the stripping of HCN in loaded organic phase were studied.The results demonstrate that TBP system can rapidly and effectively extract HCN in ammonium sulfate solutions.TBP volume fraction,initial pH of mother liquor and volume ratio of organic phase to aqueous phase(Vorg∶ Vaq) have remarkable influences on HCN extraction.At Vorg∶ Vaq of 2∶1,the mass concentration of cyanide in raffinate is less than 0.5 mg/L after a three-stage cross-flow extraction with an organic phase consisting of volume fraction 35% TBP and a total extraction ratio of cyanide is nearly 100% when initial pH of the mother liquor containing 1.71 g/L cyanide is 2.92.Moreover,the results of stripping extraction indicates that with a dilute sodium hydroxide(0.6 mol/L) as stripping liquid,cyanide single-stage stripping rate is higher than 96% by controlling equilibrium pH higher than 13.0 at Vaq∶ Vorg of 1∶1.The cyanide in loaded organic phase containing 0.78 g/L cyanide can be easily and completely stripped by a dilute sodium hydroxide(0.6 mol/L) after a two-stage cross-flow stripping at Vaq∶ Vorg of 1∶1.The poor organic phase can be reused without treatment.