Study On Treatment Of Chrome-plating Effluent Containing Chromium(Ⅵ) By Solvent Extraction

The process condition of treating electroplating wastewater containing high chromium (VI) by solvent extraction and the condition of back-extracted has been studied.Tetrabutylammonium chloride, Tetrabutylammonium bromide, TrialkylamineN235, Triisooctylamine has been chosen as extractant and kerosene, isobutylmethylketone, hexane, methylene dichloride as diluents through consulting a large amount of documents. The influence of various analytical parameters such as original concentration of extraction, ifferent solvent, pH,original concentration of Cr(VI), equilibration time,temperature etc has been discussed in detail through single factor method. The results indicated that the distribution ratio was influenced by pH, concentration of extraction, temperature and equilibration time. Through the results of the experiment, the optimum process condition were determined as follow:Tetrabutylammonium chloride- isobutylmethylketone as organic phase,concentration of Tetrabutylammonium chloride 75%, pH 0.5, organic volume to water volume 1:1, normal temperature, equilibration time 10 minutes. In this condition, the extraction efficiency can arrive at 98.6%.In the process of back-extracted, chossing the concentration 4 mol/L sodium hydroxide solution as back-extractant. The influence of various analytical parameters such as alkali to oil ratio and temperature has been discussed in detail through single factor method. The results indicated that alkali to oil ratio 1:1, the concentration of chromium in sodium hydroxide solution and the extraction efficiency will be high; improve the temperature can decrease the extraction efficiency, this phenomenon indicated that the back extracted process is exothermic process but effect lightly, so chossing normal temperature as the optimum condition.In the end, using Tetrabutylammonium chloride- isobutylmethylketone as organic phase, sodium hydroxide solution as back-extractant and the optimum process condition deal with the chrome-plating effluent from one company Guangzhou. The extraction efficiency can arrive at 98.5%.