Organic Acid Masked Aluminum (iii) Complex Characteristics And Collagen Reactive

From the aspects of equilibrium state and dynamics, pH potential titration,anti - potential titration and Ferron time - analysis were applied to research the characteristics of organic acid masked aluminum complexes solutions systematically, including alkli - resistence, poly - coordination , acid - decomposition, exsisting states and composition distributions, when the solution conditions such as the kinds of organic acid salts and their dose, kinds of aluminum salts,pH value of solutions and storage time were varied.Gel filter chromatography (GFC) and low pressure ion chromatography (LPIC) were applied to analyze the changing laws of aluminum complexes' size, composition distribution and the coordination of organic acid anions with Al3+ nucleus, varying with the solution conditions such as kinds of organic acid salts and their dose, kinds of aluminum salts and pH values; the changing laws of the ratio between the concentrations of aluminum(Ⅲ) and organic acid anions binding with A13+ necleus in different GFC fractions were studied also. Moreover, GFC preparation method and IR,27Al NMR,XRD were used to research the composition distributions and the structures of organic acid masked aluminum complexes in solutions, and the reaction properties of complexes to collagen with different tanning pH values,different dose of organic acid salts and different GFC fractions. The main conclusions were:(1) Organic acid masked aluminum complexes were active complexes which existed in three different states in solutions and could reach equilibrium state within 8 hours or so, i. e.:mono - nuclear complexes ---- 2 - 4 nucleus polymeric complexes ----"Al13 like" complexes(2) In the solution conditions similar to aluminum tanning practice, the main exsisting state of aluminum complexes was "Al13 like" complexes, which had a stiff sphere structure constructed by one [AlO4]5- tetrahedron arrounded with N(N≈9- 30) octahedral aluminum complexes by means of "mono - oxygen - bridge" or "di - oxygen - bridge". Their diameters were 8 - 16A or so.(3) In organic acid masked aluminum complexes solutions, most or almost of the adding organic acid anions were in "free" state and did not coordinate with A13 + necleus. This result was closely related to the special structure of "Al13 like" complexes. The existing states and composition distributions of aluminum complexes were mainly influenced by pH values of the solutions. The test results indicated that there was a mutation point between pH = 3 - 4. The masking function of coordinating organic acid anions mainly lay on their preventing "Al13 like" complexes to further polymerize with other aluminum(Ⅲ) complexes when the pH value rised, and the "Al13 like" complexes could be easily decomposed in lower pH value solutions, i. e. , the coordinating organic acid anions endow the "Al13 like" complexes with the property of "alkli - resistant and acid - senstive".(4) The reaction property of organic acid masked aluminum (Ⅲ) complexes with collagen not only had the common feature of metal tanning complexes, but had its own characteristics also. This was determined by the characteristics of "Al13 like" complexes - the main exsisting state of aluminum (Ⅲ) complexes in solutions. Having known the changing laws of the exsisting states and composition distributions of aluminum complexes in different solution condutions, a rational explanation for many experiment results of aluminum tanning process could be given, a foundation for the mechanistic study of aluminum tanning and aluminum cooperating- tanning was laid also.