Efficient and clean preparation of pure collagen fiber woven materials from bovine hides using alkali-activated alkaline protease

Preparing pure collagen fiber woven materials involves a series of complex unit operations by conventional process with sodium sulfide and calcium hydroxide system, resulting in high cost and serious environmental pollution. So, a green and high-efficiency ecological processing technology was designed by using alkaline protease to remove hair and open collagen fiber-bundles after pre-swelling bovine hides with alkali. In this work, the effect of hairs removal, hydrolysis of non-collagen components and penetration mechanism of alkaline protease are studied, and the properties of cross-linked pure collagen materials and the pollutants load of wastewater from the alkaline protease process after alkali pre-swelling are analyzed and evaluated to compare with those of conventional one. As a result, the hairs of bovine hides were removed completely and the proteoglycans in hides were hydrolyzed thoroughly in 30 h by alkaline protease process after alkali pre-swelling. The fibers fullness, fleeciness and grain surface smooth of cross-linked pure collagen material from the alkaline protease process after NaOH pre-swelling are better than those of the Ca(OH)2 pre-swelling and conventional processes. Especially, the chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total solids (TS) and discharged wastewater (WD) of the pollutant loads from the alkaline protease process after NaOH pre-swelling are 58%, 76.75%, 76.03% and 61.07% lower respectively than those of conventional one. This work is hopeful to provide a cleaner and simplifier method for manufacturing the ecological pure collagen based woven materials.