Dissolution of Collagen Fibers from Tannery Solid Wastes in 1-Allyl-3-methylimidazolium Chloride and Modulation of Regenerative Morphology

Collagen fibers from leather-making solid wastes were successfully dissolved in 1-allyl-3-methylimidazolium chloride ([AMIM]Cl). Polarized optical microscopy, temperature-dependent Fourier-transformed infrared spectroscopy (FTIR), and dynamic light scattering were applied to characterize the structural changes of collagen fibers during the dissolution process. The results demonstrated that a single collagen fiber could be totally dissolved in 40 min, at a maximum of 100 degrees C. During the dissolution process, the average molecular weight of the collagen chains decreased, suggesting that the structure of collagen was destroyed to some degree. Collagen was regenerated from the solution by treatment with alcohol reagents. The regenerated collagen had the characteristic structure of the initial collagen in FTIR spectra. The morphologies of regenerated collagen included nanospheres aggregation, nanosphere dispersion, and networking, which could be adjusted by changing the alcohol type, alcohol temperature, and collagen concentration. Possible mechanisms of collagen dissolution in [AMIM]Cl and regeneration were also proposed. This work demonstrates a method for recycling leather-making solid wastes and constructing collagen-based materials.