没食子酸类单宁的化学性质及对皮革中Cr(Ⅵ)的防治作用

Chemical Properties of Gallotannin and its Preventing to Cr(Ⅵ) in Leather

主要对水解类单宁橡椀、塔拉及其相应的水解单体没食子酸和鞣花酸4种物质,与Cr(Ⅲ)的络合能力、还原性、抗氧化性,及其对皮革中Cr(Ⅲ)氧化为Cr(Ⅵ)的防治作用进行了研究。以总酚值作为计量基础,取总酚值相同量的上述物质,与等量的铬粉作用,用福林酚法表征活性酚羟基的数目,从活性酚羟基的剩余数推知其络合能力,铁氰化钾还原光度法表征其还原性的强弱,DPPH光度法测其抗氧化性。主要结论:4种物质还原性和抗氧化性由大到小的排列顺序为鞣花酸、没食子酸、塔拉和橡椀,它们与Cr(Ⅲ)的络合性,在很大程度上与其对皮革中Cr(Ⅵ)的防治作用直接相关,而与其上述性质的相关性较差。

The complex ability, reducibility, antioxidation and the ability to prevent chrome （Ⅲ） from oxidation into chrome （Ⅵ） of the following malerials were investigated, that were gallotannins, valonia, gara and the main components, the gallic acid, ellagic acid. Abilities of these materials were measured by the following tests ： Given quantities of above materials on the base of equivalent phenolic value were taken to ascertain complex ability bv Folin phenol method, reducibility by absorbency method of K3 Fe（CN） 6 reducing, antioxidation against DPPH free radical by absorbency method. These parameters were considered as the in- dex of ability to prevent Cr（Ⅲ）from being oxidized into Cr（Ⅵ）. Main results are as follows： generally speaking, complex ability of these materials from strong to weak is as follows： ellagic acid, tara, valonia and gallic acid, which accords with their abilities to prevent Cr（Ⅲ） from being oxidized into Cr（Ⅵ） to a large extent. The reducibility and antioxation of these materials from strong to weak is as follows： ellagic acid, gallic acid, tara and valonia, which is different from the ability to prevent Cr（Ⅲ ）from being oxidized into Cr（Ⅵ） to some extent.