Microscopic Study on Stability of Emulsion Liquid Membrane and Extraction Efficiency of Cr(VI) from Wastewater
乳状液膜系统稳定性的显微研究及Cr(VI)离子分离效率分析

Using a capillary video microscopy technique,the stability of TBP?Span80?kerosene emulsion liquid membrane (ELM) system was investigated by preparing a single W1/O/W2 double emulsion globule. The efficiency of ELM for removing Cr(VI) was also studied. Combining these two experiments,the effects of pH,Span80,TBP and NaOH on both the stability and Cr(VI) extraction efficiency were analyzed. It was found that the oil-soluble surfactant was the key factor for the ELM stability and the system stability was enhanced with increasing surfactant concentration. In order to remove Cr(VI) effectively with ELM,the surfactant concentration must be above the minimum concentration required for the stability of ELM. Acidity reduces the stability,but it is required for the removing process,and it is favorable to the oil?water separation after the reaction. Tributyl phosphate (TBP) has no remarkable impact on the stability,however,NaOH in the internal water phase has great effect on both stability and Cr(VI) extraction efficiency. There are optimal values for all these factors to achieve the best Cr(VI) removing performance,and the extraction efficiency of Cr(VI) can exceed 99.3% after a single treatment step.