Kinetic Investigation Of Alkaline Fading Of Crystal Violet In Pseudo-binary Microemulsions Near Critical Region And Study On Extracting Nickel Ion By Microemulsion Liquid Membrane

Since Andrews,the British physicist,found the critical phenomena in1869,the research field of phase transition and critical phenomena has been very active.For different systems,it is found that their properties are similar in the vicinity of respective critical point.And the critical effect on chemical reactions is also very important.At present there are many reports about reactions just in binary solutions,but reactions in the pseudo-binary microemulsions near critical point have not yet been reported.The first part of this thesis was the kinetic study of alkaline fading of crystal violet in water/AOT/n-decane and water/CTAB/n-butanol pseudo-binary microemulsion near and far away from respective critical point by UV-visible spectrometer.Microemulsion as an extracting membrane not only has many excellent and outstanding advantages,including small and highly dispersed particles,large mass transfer area and high mass transfer efficiency,but also overcomes the disadvantages of emulsion,including the instability, easily swelling,and hard demulsification.Nickel,as a very important industrial raw material of the catalysts,batteries,alloys,ect.,has a wide range of applications,so in the second part of this thesis microemulsion as a novel extraction method of nickel ion was examined.The specific content of the thesis as following:(1) Kinetic studys of alkaline fading of crystal violet reaction were investigated in water/AOT/ n-decane(LCST,lower critical solution temperature)ω=40.8 andω=45.2(n_water/n_surfactant molar ratio) near and far away from respective critical point.When the temperature was much lower than T_C(low critical point of the solution),the reaction rate constant obeyed the Arrhenius equation.But when the temperature was less than T_C about 0.200-1.500 K,namely near critical region,the reaction rate constant deviated from Arrhenius equation and appeared to Speeding up phenomenon,which wasn't consistent with the theories of critical slowing down in dynamic critical phenomena.The fitted critical exponents,including x= 0.322±0.028(ω=40.8) and x=0.340±0.034(ω=45.2),were also not in agreement with G-W's theory.(2) The kinetic investigation of alkaline fading of CV had also been examined in water/CTAB/ n-butanol(UCST,upper crical solution temperature)ω=146 psuedo-binary microemulsion. The reaction rate constant was in good line with the Arrhenius equation when the temperature was much higher than T_C(upper critical point of the solution),and it appeared the critical slowing down when the temperature got closed to T_C,just above it in range of 0.646-2.282 K.The fitted critical exponents,x=0.124±0.028 closed to 0.11(the value ofαin 3DIsing model),was also in agreement with G-W's theory.(3) As a byproduct of kinetic investigation of alkaline fading of CV in pseudo-binary microemulsions,we had observed that comparative amount of two isomers of CV changed in both LCST and UCST microemulsions.I_λ590/I_λ550,the intensity ratio of the maximum absorption wavelength to the shoulder,switched from increasing to decreasing in the nearest region of T_c,was influnced by the critical effect.(4) In order to test the extracting effect of water/AOT/n-decane microemlsion as a novel liquid membrane to nickel ion,we had devised two experiments,including the standard nickel ion solution and the industrial one.We found the extraction and anti-extraction rate were influenced by the experimental parameters including not only liquid membrane composition, pH,the quality ratio of the membrane to nickel ion solutions,but also stirring time.The results showed that when the composition of the liquid membrane,the quality ratio of AOT to n-decane,was between 7/3 and 6/4,the microemulsion was very efficient to the extraction of nickel ion solution,and could be recycled several times to utilize as long as the proper pH value was adjusted.After extracting the industrial nickel ion solution 9 times with pH in the range of 9-10,nickel ion concentration was up to 44.170 g/L,104 times to the original industrial nickel ion concentration(0.423 g/L).