Removal of chromium(III) from aqueous waste solution by predispersed solvent extraction
(College of Chemical Engineering, Sichuan University, Chengdu 610065, China)
Abstract: The extraction experiments of chromium(Ш) from aqueous waste solution by predispersed solvent extraction (PDSE) process with extractant (HEHPEHE) and its mixture, including acidic extractant (D2EHPA), alkaline extractant (TOA) and neutral extractant (TBP) were carried out respectively. It is found that the extractant HEHPEHE exhibited high extraction selectivity to chromium(III) from aqueous waste solution. The colloidal liquid aphrons (CLAs) were successfully generated using kerosene as a solvent, HEHPEHE as an extractant, sodium dodecyl benzene sulphate (SDBS) as a surfactant in aqueous phase and polyoxyethylene sorbitol anhydride monolaurate (Tween-20) in oil phase. To study the extraction efficiency and advantages of the PDSE process in the removal of chromium(Ш), the effects of major factors, such as initial chromium(Ш) concentration, volume of colloidal gas aphrons (CGAs), HEHPEHE volume fraction, phase ratio (solvent phase to water phase), mass fraction of dodecyl trimethylammonium bromide (HTAB), mass fraction of SDBS, mass fraction of Tween-20 and initial pH of aqueous waste solution were also investigated and the appropriate process conditions were obtained. Under the appropriate conditions, the extraction efficiency of chromium(III) above 99.9 % can be achieved and the treated aqueous waste solution can be discharged directly without polluting the environment.
Key words: predispersed solvent extraction (PDSE) process; chromium(Ш); extraction mechanism; extractant