The Comparative Studies Of Enrichment And Determination Of Cadmium By Ionic Liquid Aqueous Two-phase Extraction And Flotation

The cadmium,an unnecessary element in the human body,is the compound state in nature usually.With the rapid development of modern industry,the waste water which was discharged from all kinds of factories containing cadmium ion have polluted the environment and endangered human health.The cadmium was accumulated in human body by food and drinking water which were the important transmission routes of cadmium pollution.At present,the main method of separation of cadmium ion concentration with liquid-liquid extraction,adsorption separation,liquid-liquid extraction method which is easy to cause two pollution to the environment.Therefore,the new technology research about separation and enrichment of heavy metal ions in water has become the subject of concern.In this project,based on a comprehensive study of the results of massive literatures,a new method about the ionic liquid-aqueous two-phase extraction?ILATPE?and ionic liquid-ester-flotation?ILEF?was established in the concentration and determination of cadmium combined with ultraviolet spectrometry.The method,which open up a new way in the concentration and separation of cadmium,was used in the pretreatment of heavy metal cadmium of environmental water in this research.The main results of this study are as follows:?1?The synthesis and purification of ionic liquid were studied.Firstly,the [bmim]Br intermediates were synthesized from imidazole and n-butyl bromide.Afterwards,The imidazolium ionic liquid [bmim]BF₄ was prepared by the ion exchange reaction of intermediates and sodium tetrafluoroborate under certain conditions.Finally,the crude product of [bmim]BF₄ was purified by methylene chloride to obtain the pure reagent.The study laid a good foundation for us to grasp and understand the characteristics and the application prospects of ionic liquids,and provided a basis for the development of this research.?2?The optimum conditions for the formation of ternary ionic associate?Rh B?2?Cd I4?which is formed by the standard reagents of Cd2+,KI,RhB was studied,and the response surface methodology was used to optimize the reagent dosage in a single factor experiment.Under acidic conditions,Cd2+ can form an ionic compound Cd I42-with KI,and rhodamine B can combine with it to form a ternary ionic associate?Rh B?2?Cd I4?which was detected by UV spectrophotometer and the absorption peak was red shifted.This shows that KI and rhodamine B were the good collector of Cd2+ of test solution.because of the good hydrophobicity of ternary ionic associate,an important prerequisite was provided for the separation and extraction of trace heavy metal cadmium in the next experiment.Then,The optimum dosage of HAc,KI,RhB,and the optimal reaction time for the formation of?Rh B?2?Cd I4?were obtained by single factor experiment and response surface methodology.Finally,the standard curve of the?RhB?2?Cd I4?system was obtained,and the linear regression equation was y=0.02511x+0.34407,R2=0.98988.?3?The [bmim]BF₄ ionic liquid aqueous two-phase extraction?ILATPE?of Cd2+ in water samples was studied.First of all,the best phase separation salt was determined by comparison and selection.Then,in order to compare ionic liquids with traditional organic solvents,the phase diagram was drawn by applying turbidity analysis to investigate the phase formation rule of aqueous two-phase extraction.The ternary ionic associate formed in optimal condition was used in the ILATPE to study the optimal condition of pH and temperature.Finally,the standard curve of the ILATPE was obtained,and the linear regression equation was y=0.02511x+0.34407,R2=0.98988.The recovery rate is greater than 91% of the actual determination of Cd???in environmental water samples.?4?The separation and enrichment of Cd???in environmental water samples by ILEF with the [bmim]BF₄ ionic liquid was studied.The effects of solution acidity,flotation time,gas flow rate,surfactant and coexisting ions on the flotation system were discussed.The Cd???can react with KI and RhB to form the strong hydrophobic ternary ionic associate?RhB?2?Cd I4?which can be extracted from aqueous phase by using ILEF in the presence of HAc-NaAc buffer solution.Then,the standard curve of the ILEF was obtained,and the linear regression equation was y=0.0469x+0.30629,R2=0.99407.The recovery rate is greater than 95% of the actual determination of Cd???in environmental water samples.Based on the above study,Cd???can react with KI and RhB to form the ternary ionic associate which can be separated and enriched by ILATPE and ILSFS.The rapid determination of trace Cd???and the process of green pollution-full residues can be achieved.The method,which has the good potential application value and the application prospect,not only added new contents for the green chemistry research,but also completely conformed to the international environmental protection important idea since twenty-first century.