Degradation Of Ionic Liquids In Zerovalent Zinc/Activated Carbon Microelectrolysis System

Ionic liquids（ILs）,composed of organic cations and inorganic or organic anions,are salts which are liquid at near room temperature.Due to its unique physical and chemical properties,ionic liquids are increasingly favored by scholars at home and abroad and widely used as green solvents.In fact,ionic liquids are not really"green",but potentially toxic to humans.Therefore,when the ionic liquid is improperly processed and enters the nature through wastewaters,it will certainly cause damage to the environment and seriously threaten human health.While focusing on the application of ionic liquids,researchers began to explore the removal methods of ionic liquids.This paper studies the degradation of common ionic liquids by ultrasound-assisted zero-valent zinc/activated carbon micro-electrolysis technology,aiming to find effective degradation methods of ionic liquids and provide data reference for wastewater treatment and ecological environmental protection.The main experimental contents include:（1）Degradationof1-butyl-3-methylimidazoliumtetrafluoroborate（[C4mim][BF4]）ionic liquid was conducted by ultrasound-assisted zero-valent zinc/activated carbon micro-electrolysis system（US-ZVZ/AC）.Degradation effect of[C₄mim][BF₄]was observed by changing pH value,carbon zinc ratio and carbon zinc dosage.The results showed that the degradation efficiency of[C₄mim][BF₄]was the highest when the pH value was 3,the carbon to zinc ratio was 1:1,and the amount of carbon and zinc were both 6g/L,with the degradation degree of over 92%after the reaction for 120min.（2）The degradation of imidazolium ionic liquids with different cations([C₂mim][BF₄],[C₄mim][BF₄],[C₆mim][BF₄],[C₈mim][BF₄],[C₁₀mim][BF₄])in US-ZVZ/AC system under the optimized conditions was studied.The results showed that the degradation degree of the above five ionic liquids in the US-ZVZ/AC system was above 80%.The degradation rates of the five ionic liquids follow the following sequence:[C₂mim][BF₄]>[C₄mim][BF₄]>[C₁₀mim][BF₄]>[C₆mim][BF₄]>[C₈mim][BF₄].Among them,[C₂mim][BF₄]was degraded completely at 120 min of reaction time.It is shown that the degradation rate of the imidazolium ionic liquid decreased with the increase of alkyl side chain length except[C₁₀mim][BF₄].The degradation of imidazolium ionic liquids with different anions showed that the degradation degree of[C₄mim][HCO₂]and[C₄mim][CH₃CO₂]could reach more than70%at 120min,while the degradation efficiency of[C₄mim][C₆H₅CO₂]was very low,only 20.4%.The degradation rate of imidazolium ILs with different anions is different,and the degradation rate decreases with the increase of anion volume.（3）Determination of short-chain fatty acids and anions generated in the degradation of 1-alkyl-3-methylimidazolium tetrafluoroborate（[C_nmim][BF₄],n=2,4,6,8,10）ionic liquids was carried on with ion chromatography.The results showed that different concentrations of formate ion and nitrate ion were detected during the degradation of[C_nmim][BF₄].The measurement of total organic carbon（TOC）showed that the TOC removal of the imidazolium ionic liquid tested was above 85%after 120 min of degradation time.It can be seen that the US-ZVZ/AC micro-electrolysis technology can be used to degrade imidazolium ILs effectively.The research results in this paper may be useful for eliminating influence of ILs on the environment.