Synthesis and Characterization of Superabsorbent Hydrogels From Waste Bovine Hair Via Keratin Grafted With Acrylic Acid (AA) and Acrylamide (AAm)

The leather industry is known as one of the potentially hazardous and polluted sectors due to the large consumption of water and chemical materials. There are many companies with a high level of environmental protection systems in the leather industry, with Zero Hazardous Substances Certificate and using chemical materials with exhaustion yield. There is also a great effort to replace and reduce potentially hazardous materials, petroleum origin materials, and solid waste generated by hide processing. It is not only about discharging chemicals to the environment but also about releasing valuable biomass sources (collagen, keratin, etc.). Bovine hair is one of the low biodegradable wastes during bovine leather processing. In this study, bovine hair was converted to keratin hydrolysate (KH) by an alkaline process. KH was selected to enhance the biocompatibility of the hydrogel and grafted with acrylic acid (AA) and acrylamide (AAm) monomers to obtain superabsorbent hydrogels. Polymerization was conducted in the presence of N, N'-methylene bisacrylamide (NMBA) which was used as a cross-linking agent, and ammonium persulfate (APS) as an initiator. Different keratin/monomer ratios, cross-linking agents, and initiator amounts were kept as variables to aim for the highest swelling capacity. Synthesized hydrogels were chemically, morphologically, and thermally characterized via Fourier Transform Infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimeter (DSC), and thermal gravimetric analyzer (TGA). FTIR, DSC, and TGA results confirmed the grafted structure. The maximum swelling ratio was recorded at pH 9, at the end of 48 h as 1791%. Sponge-like hydrogels were successfully synthesized, and waste keratin was successfully valorized through hydrogels which can be used in high-value-added areas such as health, agriculture, hygienic products.