Modification of ultrafine silk fibroin powder for efficient oil/water separation

Abstract

In this study, silk fibroin powder (SFP) was modified using silane coupling agent vinyltrimethoxysilane (KH 171) to produce hydrophobic particles with micro–nanostructure. A series of tests and analyses on the microstructure and properties of the SFP before and after the modification show that silane oligomer (PSO) nanoparticles are formed on the SFP after the modification with KH 171, reducing its surface energy and constructing micro–nanoscale rough structures. Moreover, the modified SFP can maintain a high hydrophobicity after long-term washing. The hydrophobic modification of SFP has no significant effect on its crystal structure, but markedly improves its thermal stability by introducing PSO nanoparticles. A comparative study was performed on the samples of original SFP, KH 171-modified SFP, PSO nanoparticles, and SFP + PSO mixture using FTIR, TGA, and contact angle measurements. The results provide compelling evidence from different perspectives that the PSO nanospheres, formed by the hydrolysis and condensation of KH 171, are covalently bonded to the SFP, not just simple physical adsorption. This system successfully separated several oil/water mixtures and water-in-oil emulsions, with separation efficiencies of 99.1 % and 99.95 %, respectively. This indicates that the hydrophobic modification of the SFP and its use as a material for oil/water separation have practical feasibility. This provides new concepts for the recovery and reuse of discarded silk fibers, expands the application fields of SFP, and has good application prospects.