Degradation Of Functional Ionic Liquids In Zero-valent Zinc/Activated Carbon System

[BACKGROUND]Ionic liquids（ILs）refer to molten salts,which composed of cations and anions,with a melting point lower than 100℃.They are increasingly used in various fields of production and life because of theirs unique physical and chemical properties,such as low vapor pressure,high thermal stability,and wide liquid range.With more and more research of ionic liquids,people gradually discover that they are not only ecologically toxic but also are difficult to be degraded,which are harmful for environment if the generated wastewater and waste liquid are directly discharged into the natural environment without treatment.Therefore,ionic liquids need to be degraded in order to meet the development of green ecology.[OBJECTIVES]The degradation condition of functional ionic liquids in the ultrasound-assisted zero-valent zinc/activated carbon system（US-ZVZ/AC）were explored to observe the degradation effect,providing a theoretical basis for the treatment of ionic liquid waste.[METHODS]1.The degradation of 1-allyl-3-methylimidazolium chloride（[Amim]Cl）was conducted by the ultrasound assisted zero-valent zinc/activated carbon system.The degradation effect was observed by changing the p H value of the solution,the ratio of carbon and zinc and the amount of carbon and zinc.2.Under the best experimental conditions,cations and anions that may be generated by the degradation of 1-allyl-3-methylimidazolium chloride（[Amim]Cl）,N-butyl,methyl benzimidazolium bromide（[Bmbim]Br）and tetrabutyl ammonium chloride（[Tba]Cl）ionic liquids were analyzed through ion chromatograph.3.The total organic carbon（TOC）and degradation rate of three ionic liquids by the ultrasound assisted zero-valent zinc/activated carbon system was studied and at the same time,the degradation products of them were analyzed by GC-MS.[RESULTS]1.The results revealed that when the p H of solution was 7,the ratio of carbon and zinc was 3:1,the dosage of activated carbon was 6g·L^-1and the dosage of zinc powder was 2g·L^-1,the degradation effect of[Amim]Cl was the best and the degradation rate was more than 93%after 80min.2.The results showed that no NH₄^﹢was detected in[Amim]Cl ionic liquid degradation solution;HCO₂^﹣increased slightly,suggesting that a small amount of HCO₂^﹣may be generated during the degradation process of[Amim]Cl;NH₄^﹢was detected in[Bmbim]Br degradation solution,indicating that it was generated during the degradation process,which should be generated by N atoms after opening the ring of imidazole;NH₄^﹢was detected in[Tba]Cl ionic liquid degradation solution,indicating that it was generated during the degradation process;comparing with the beginning of degradation,the content of Cl^﹣had an upward trend,and it was speculated that Cl^﹣was gradually released in the degradation process of[Tba]Cl.3.The mineralization rates of[Amim]Cl,[Bmbim]Br and[Tba]Cl degradation were 88.6%,78.0%and 69.9%respectively after 110 min.In addition,the intermediate products degraded by[Bmbim]Br and[Tba]Cl were detected at different times.[CONCLUSIONS]In general,the ultrasound-assisted zero-valent zinc/activated carbon system is very effective for the degradation of functional ionic liquids with low cost and simple operation,and is expected to be applied to the treatment of ionic liquids wastewater on a large scale.