Effect of collagen hydrolysate obtained from leather waste on the setting, hydration and crystallization process of gypsum

Abstract

The disposal of leather waste has always been a huge challenge facing the tannery. Thus, the effective conversion of leather waste into value-added products can help the leather industry achieve green and sustainable development. In the paper, we utilized collagen hydrolysate (CH) obtained from leather waste as a protein retarder for gypsum and the effect of CH on the setting, hydration and crystallization process of gypsum was analyzed. The results showed the addition of CH delayed the increase in hydration degree and release of hydration heat during the hydration process of gypsum, and this delay action was more remarkable as more CH was introduced. Moreover, CH could postpone the crystallization of dihydrate gypsum from a micro perspective. TG/DSC, FTIR, XRD, and SEM analysis indicated that the presence of CH inhibited the hydration reaction hemihydrate gypsum and the formation of dihydrate gypsum but over time the hemihydrate gypsum was completely hydrated at last. Finally, the retardation mechanism of CH on the gypsum was investigated by adsorption and zeta potential measurements. Adsorption and zeta potential measurement results demonstrated that CH could inhibit the hydration process of hemihydrate gypsum by adsorbing on the gypsum particle, thereby achieving the retarding effect.