分别应用含羧基的嗯唑烷和乙醛酸对皮粉进行化学改性,提高对铬鞣剂的吸收率以达到减少铬鞣污染的目的。结果表明,在303K,pH值为4.5条件下,白皮粉对铬吸收量W(CP^3+/W(皮粉)为15.91mg/g,低于乙醛酸改性皮粉的铬吸收量25.45mg/g和嗯唑烷改性皮粉的铬吸收量33.57mg/g。含羧基嚼唑烷改性皮粉吸收铬共分两个阶段进行:一个快速初级阶段和缓慢的第二阶段。快速阶段约1h,吸收量为50%;4h后基本达到吸收平衡,此时吸收量为33.07mg/g。在303,308,313,318K条件下嗯唑烷改性皮粉最高吸收量分别为33.57,37.78,45.5,57.14mg/g。乙醛酸、嚼唑烷与胶原上的活性基团发生化学反应,将羧基、羟基等基团引入皮胶原,增强了胶原对铬的吸收能力。
GlYoxylic acid and oxazolidine with carboxyl groups were applied for modification of collagen. As a result, the additional carboxyl groups were introduced to the side-chain of collagen and extra combining point for chromium tanning agents was achieved. The hide powder modified with oxazolidine can adsorb 33. 57 mg/g chromium( Ⅲ ) from an aqueous solution at pH =4.5 and T=303 K, which was higher than the adsorption of hide powder modified with glyoxylie acid (25.45 mg/g) or un-modified hide powder (15.91 mg/g). For the case of hide powder modified with oxazolidine, the adsorption of chromium(Ⅲ) can be divided into two steps, a primary rapid step and a secondary slow step. The rapid step lasted for about 1 h and 50% and chromium( Ⅲ ) adsorption was completed in this step. The maximum chromium( Ⅲ) adsorption of 33.07 mg/g was achieved after 4 h. The adsorption capacity of hide powder depended on the temperature and higher temperature was beneficial for the adsorption of chromium(Ⅲ), for example, maximum adsorption capacities of 33. 57 mg/g, 37.78 mg/g, 45.53 mg/g and 57. 14 mg/ g were observed at 303 K, 308 K, 313 K, and 318 K, respectively. The high exhaUstion chromium (Ⅲ) mechanism of modified collagen was suggested to be that. glyoxylic acid and oxazolidine reacted with collagen and formed firm covalent bond, and then the carboxyl groups, hydroxyl groups of glyoxylic acid and oxazolidine were introduced onto the backbone of collagen. In the adsorption process, the carboxyl groups of glyoxylic acid and oxazolidine together with carboxyl groups of collagen coordinated with chromium (Ⅲ), which contributed to the hide powder high chromium( Ⅲ ) adsorption.