The conventional beamhouse of leather making invariably results in serious pollution of sulfide, solid suspension and ammonia nitrogen because of the use of Na 2 S and Ca(OH) 2 in unhairing (liming) and reliming. It is an urgent issue to develop alternatives of the Na 2 S and Ca(OH) 2 system. In this work, the K + and Cl − of Hofmeister series are chosen to improve the binding ability of dispase to water molecules and substrate, which can further enhance the unhairing/fiber opening effect of dispase, with only one step for unhairing, opening collagen fiber-bundles and bating. The cycle unhairing effect of K + /Cl − /dispase solution system and its unhairing waste-water recycling in fiber opening are studied. The effect of K + and Cl − on the penetration of dispase in bovine hides, the hydrolysis for proteoglycans and elastic fibers, and the opening effect for collagen fiber-bundles are analyzed systematically. The results indicated that, the K + and Cl − increase the stability of dispase activity to 12 times of recycling for unhairing. Due to the electrostatic attraction of K + and Cl − to the charged amino acid residues, both the penetration of dispase in bovine hides and the hydrolysis of proteoglycans and elastic fibers are accelerated, and an easy step for unhairing/fiber opening is realized. Only 30 h is needed for unhairing/fiber opening, and the waste-water can be recycled for unhairing too. Because of the reuse of unhairing waste-water, low pollutant loads , high collagen fibril dispersity are reached. The resultant leathers are good in physical properties, and their thermal stability are comparable to that by the conventional process. The leather making system of KCl/dispase is suggested to be a cleaner and greener technology than the conventional ones.
Mingrui Zhang,Chao Tang,Hui Liu,Shufa Qin,Jie Liu,Mǎdǎlina Georgiana Albu Kaya,Keyong Tang
Tanneries are increasingly focusing on environmentally friendly processes, emphasizing the concept of clean production to minimize the environmental impact. This study investigated the eco-friendly application of an α-amylase/neutral protease system (ANS) in a single-step process for unhairing, fiber opening, and bating, providing an effective alternative to the conventional complex chemical-based lime-sulfide system (LSS). A mathematical model was established using response surface methodology (RSM) to optimize the operational conditions, yielding a 0.3 wt% α-amylase/0.5 wt% neutral protease solution at 28.4 °C for 16.6 h. The effects on unhairing and fiber opening were evaluated using scanning electron microscopy (SEM), while the effect on bating was accessed by the removal of carbohydrates and proteoglycans. The obtained leathers had comparable physical properties to their conventional counterparts, with enhanced hydrothermal shrinkage temperature and softness. In terms of environmental benefits, the optimized ANS could significantly decrease more than 90% of the chemical oxygen demand (COD), NH3–N, and Cl−, respectively, along with a 73.91% reduction in total solids (TS). Cost analysis indicated direct savings with a significant cost reduction of 30.98% of the ANS compared to that of the LSS, as well as additional indirect cost reduction through improved production efficiency and streamlined wastewater treatment processes. The use of electricity and water was reduced by 44.6% and 93.9%, respectively, which could reduce greenhouse gas emissions by 44.6%. This study highlighted the potential of α-amylase/neutral protease as a sustainable and cost-effective alternative in leather manufacturing that aligns with environmentally friendly practices.
危险品化学品经营许可证（带存储）