Hydrogel beads derived from chrome leather scraps for the preparation of lightweight gypsum

Leather industry generates lots of hazardous leather waste every year. Among these leather wastes, chrome leather scraps can be effectively utilized to produce added-value products. In this study, hydrogel beads were prepared through a series of processes that included degradation of chrome leather scraps, purification and concentration of the degradation liquid, gelation of the degradation liquid and crushing of the hydrogel. The prepared hydrogel beads were successfully dispersed in gypsum slurry and then dried to prepare lightweight gypsum. The prepared lightweight gypsum exhibited high porosity (22.64∼55.37%) and low density (0.76∼1.47 g/cm3) due to the incorporation of hydrogel beads. The pore sizes of lightweight gypsum can be adjusted by changing the level of hydrogel beads during preparation. However, the presence of a porous structure in the lightweight specimen decreased its mechanical performance. The thermal conductivity of this type of lightweight gypsum decreased from 0.383 W/m⋅K to 0.190 W/m⋅K with an increasing incorporation of hydrogel beads, indicating that it is a promising candidate for thermal insulation applications. Furthermore, this lightweight gypsum also exhibited excellent sound absorption performance compared with that of gypsum without the addition of hydrogel beads. This study not only promotes the recycling of leather waste but also has significance for the development of novel building materials.