Study On Complex Behavior Of Trace Copper In Complicated Chloride Solutions

It is well known that the complicated chloride systems which including copper play an important role in the modern production and people's life, so there are many researchers have made studies on this kind of solution to get more and more information about the competitive complexation reaction between copper(II), chlorine ion and water molecule. But all these investigate ignored the relation of solution structures and properties in their discussion about this kind of solution. A systemic study on the solution structures and properties of complex chloride systems is necessary to be made. Therefore, in our study, the relationship between the solution structures (species distribution) and system properties (chlorine concentration, component activities, properties of chlorine ion contribution radicle, and so on) of the complicated chloride systems MCln-CuCl2-H2O(M=Li, Na, K, Mg, Ca) were studyed on the base of UV-Vis spectra investigate. Then the component activities (including water activity) were analyzed and the stability constants of every species were calculated. Our study will be able to provide a theoretical guidance to the correlative researches, material preparation, chemical production process, and so on. The main work of this paper as follows:(1) The UV-Vis spectra of LiCl-CuCl2-H2O, NaCl-CuCl2-H2O, KCl-CuCl2-H2O, MgCl2-CuCl2-H2O and CaCl2-CuCl2-H2O systems were detected with UV-Vis spectrophotometry. The copper concentration in these solutions is always 5.0×10-4 molarity. Then the changes which presented in the UV-Vis spectrogram of every different system were analyzed, and the number of components which do contributions to the spectra could be concluded at the first time.(2) The principal component analysis (PCA) would be applied on absorbance data processing in order to make sure the number of absorbing complexes which is necessary to describe the experimental spectra. Multiple Curve Resolution program "MCR-ALS" whose theoretical base is "model-free" analysis should be used to resolve the experimental spectra so as to get the molar absorption spectrum and fractions of individual complexes in every system.(3) The current single electrolyte solution theory used to describe the individual ion activity coefficients were evaluated, and the distinctions between theoretical values and experimental values of chlorine ion activity coefficients in LiCl, MgCl2 and CaCl2 solutions would be analyzed. By combining the correct chlorine ion activity coefficients, component activity (including water activity) and fractions data of individual complexes in every system, the stability constants of every copper(Ⅱ) chloride complexes can be obtained finally.By analyzing the experimental spectrogram and the fractions of individual complexes in the LiCl-CuCl2-H2O, MgCl2-CuCl2-H2O and CaCl2-CuCl2-H2O systems whose chlorine concentration are high and number of components are the same, we discovered that the influences of alkali metals and alkaline-earth metals cations Li+, Mg2+and Ca2+towards the formation reaction of copper(II) chloride complexes are different, and the influence of Mg2+is biggest, the next is the Li+and Ca2+. Besides, the analysis on the stability constants of copper(Ⅱ) chloride complexes in the three systems indicated that the water activity must be considered in the calculation of stability constants of copper(Ⅱ) chloride complexes. This result showed to us that the effect of water to the complexation balance of between copper(Ⅱ) and chlorine ion can't be ignored.