Functionality of nano and 3D-microhierarchical TiO₂ particles as coagulants for sericin extraction from the silk degumming wastewater

Amine-functionalised TiO₂ particles were employed as coagulants to remove sericin from the silk degumming wastewater. Two types of TiO₂ particles including 3D-microhierarchical TiO₂ (Micron-size) and TiO₂ nanoparticles (Degussa P-25) were used in this study. The surfaces of both types of TiO₂ particles were functionalised using 3-aminopropyl trimethoxysilane (APTMS). The impacts of TiO₂ type, pH, TiO₂ concentration, and settling time on sericin removal efficiency were investigated. The efficiency of TiO₂ particles in sericin removal was evaluated by measuring the residual turbidity and UV-vis spectra of the solutions before and after the treatment. Moreover, the COD, SDS-PAGE and protein assay tests were conducted to further analyse the treated solutions. The results demonstrated that the sericin removal efficiency of around 67% and turbidity reduction of 95% were achieved at the optimum conditions of 0.04 g TiO₂, pH = 5, and 60 min settling time. Nano and micron-size TiO₂ particles showed similar efficiency for sericin removal, but micron-size particles outweighed due to their higher efficiency in inducing greater turbidity reduction after 60 min. The obtained sericin/TiO₂ composites were stable after several cycles of wash and could be useful in different fields including cosmetic, and textile finishing, among others.