以消除铬污染为目标的制革单元过程重组与耦合优化研究

The elimination of chrome pollution is a key technical issue that needs to be urgently solved in leather industry. However, chrome is inevitably released into effluents during chrome tanning and all the post tanning processes by using existing technologies, which makes it almost impossible to eliminate chrome discharge from leather processing. In order to achieve a convenient and complete recovery of chrome from tannery wastewater as well as high quality of resultant leather, a novel leather processing system, composed of beamhouse, chrome-free pretanning and charge adjustment, post tanning and end chrome tanning, will be developed by reassembling and coupling the unit processes of leather manufacture. The main contents of the project will include: 1) synthesis and structure-activity relationship of a type of amphoteric polymer tanning agent which is suitable for chrome-free pretanning process; 2) enhancement of tanning effect and regularities of adjustment of leather charge in chrome-free pretanning process; 3) optimization of the coupling of chrome-free pretanning process and post tanning process, including methods and principles of the supplemental adjustment of isoelectric point of leather for strengthening the affinity of post tanning chemicals for leather during post tanning; 4) optimization of the structure of chrome tanning agent and tanning conditions for end chrome tanning process; 5) mechanism of optimization of the coupling of all unit processes, and key factors of process balance. This project will hopefully provide leather industry with new methods and a sound theoretical basis for the elimination of chrome pollution.

铬污染的消除，是制革工业持续发展迫切需要解决的关键科技问题。采用现有制革技术，铬鞣及铬鞣之后的所有水相操作工序都会排放铬，这使得完全消除制革过程的铬排放几乎不可能实现。针对这一问题，本项目拟通过对制革单元过程实施重组和耦合优化，构建"准备单元-无铬预鞣与电荷调控单元-染整单元-末端铬鞣单元"为主线的新的制革工艺体系，在保证成革品质的同时，使铬的完全回收利用变得简单易行。主要研究内容包括：1）支撑无铬预鞣实施的两性聚合物鞣剂的合成方法及其构效关系；2）无铬预鞣过程鞣制效应的强化及皮革电荷性质的调控规律；3）无铬预鞣与染整过程的耦合优化，包括染整过程中进一步调控皮革等电点、强化其与染整化学品亲和力的方法和原理；4）适合于末端铬鞣过程的铬鞣剂结构及鞣制条件的优化；5）所有单元过程耦合优化的科学原理及工艺平衡的关键要素- - 为彻底消除制革工业的铬污染提供新的方法和系统的理论基础。

铬污染的消除，是制革工业持续发展迫切需要解决的关键科技问题。采用现有制革技术，铬鞣及之后的所有工艺过程都会排放铬，使得完全消除制革过程的铬排放几乎不可能实现。针对此问题，本项目通过对制革单元过程实施重组和耦合优化，构建了“准备单元—无铬预鞣与电荷调控单元—染整单元—末端铬鞣单元”为主线的新型制革工艺体系，在保证成革品质的同时，使铬的完全回收利用变得简单易行。主要研究内容和结果包括：1）通过曼尼希反应和自由基聚合反应的联用，合成了分子中含有醛基、氨/季铵基和羧基的两性聚合物鞣剂；通过系统研究Al/Zr摩尔比、配体种类、金属/配体摩尔比等对铝-锆鞣剂鞣革性能的影响，制备了以深度氧化淀粉为配体的铝锆配合物鞣剂。2)通过调控鞣剂结构和优化无铬预鞣条件，获得了湿热稳定性达到削匀要求、胶原纤维分散良好、等电点较高的两性聚合物预鞣革和铝锆配合物预鞣革，为染整和末端铬鞣单元的顺利实施奠定了基础。3）完成了无铬预鞣和染整单元的耦合优化研究，结果表明：采用两性聚合物预鞣革时，需适时引入两性助剂调控皮革等电点、强化其与染整材料的亲和力，从而提高染整材料的结合强度；采用正电性强的铝锆配合物预鞣革时，合理搭配使用阴离子染整材料有利于调控皮革的电荷性质，促进染整材料的均匀分布。4）完成了末端铬鞣单元鞣制条件的优化，在染整单元之后成功实施了末端铬鞣，铬鞣剂在革内渗透均匀、结合牢固，成革的综合性能提升，风格明显向铬鞣革转变。采用耦合优化的“无铬预鞣单元—染整单元—末端铬鞣单元”制革工艺体系，预鞣和染整单元的所有过程不再产生含铬废水和含铬固废，含铬废水仅集中于末端铬鞣单元，产生量降低80%以上，易于单独收集处理。综上所述，该制革工艺体系具有重大的应用前景，为彻底消除制革工业的铬污染提供了新的方法和系统的理论基础。