Mesoporous silica modified zwitterionic poly(ionic liquids) with enhanced absorption for Cr3+ and dye as a tanning agent

Zwitterionic poly(ionic liquids) (ZPILs) were used as a combination tanning agent to enhance the absorption of chromium tanning agent and dyes simultaneously, which is crucial and challenging during the tanning process. Mesoporous silica (MCM-48) with a size of ∼70 nm was introduced as a nanotainer to adsorb photoinitiator and a small quantity of methylacrylic acid (MAA), and then ILs monomer and MAA were added and they started to polymerize in the pores of MCM-48, which could avoid the gelation of ZPILs in aqueous solution. In this way, the obtained nanocomposites (M48/PMIL) had a smaller size (200–500 nm) and good fluidity, so they were suitable to use as tanning agent. The addition of M48/PMIL made the shrinkage temperature and thickness rate of leather increase by 5.5 °C and 22 % than Cr-tanned leather, respectively. Meanwhile, mechanical properties are also improved further. Moreover, the Cr 2 O 3 content in tanning liquor decreased by 28.8 %, and the anionic dye absorption rate enhanced by 7.9 %, respectively, due to the good permeability and the presence of zwitterion in M48/PMIL. This novel tanning agent exhibits a potential application in less chromium tanning and decreases the Cr 3+ and dye content in tanning liquor.