Preparation of auto-suspending hollow silica microfiber derived from biotemplate and its highly selective adsorption for organic dyes

Hollow silica microfibers (HSFs) are successfully prepared by the sol-gel process with cotton fiber as biotemplate. The as-prepared HSFs can auto-suspend into aqueous solution due to the higher negative zeta potential, and the auto-suspension performance can be conveniently tuned. The adsorption behaviors of methylene blue (MB) and methyl violet (MV) onto HSFs-0.15 are investigated in details. The results show that MB and MV can be strongly adsorbed onto HSFs-0.15 from dye-containing wastewater. The adsorption kinetics of HSFs-0.15 for MB and MV adsorption are better fitted by the pseudo-second order model. Boundary diffusion process and intra-particle diffusion process are involved into the adsorption process. The adsorption isotherm of MB and MV onto HSFs-0.15 can be well described by Langmuir model, indicating that adsorption of MB and MV onto the surface of HSFs-0.15 is monolayer and heterogeneous. The maximum adsorption capacity calculated from Langmuir isotherm model are 301.2 and 62.89 mg g–1 for MB and MV, respectively. The adsorption of MB and MV onto HSFs-0.15 is slightly influenced by pH due to the higher negative zeta potential of HSFs-0.15. The proposed mechanism based on the experimental results highlights that the adsorption is mainly controlled by electrostatic interaction. Moreover, the as-prepared HSFs-0.15 can selectively collect cationic MB and MV for the mixed solution due to the strong electrostatic interaction. Furthermore, the auto-suspension of HSFs-0.15 before adsorption and the automatic settlement after adsorption in aqueous solution can eliminate energy-consuming mechanical stirring for adsorption operation in practical application. These results show that the as-prepared HSFs using biotemplate has the potential to the selective adsorption and separation of cationic organic pollutant in wastewater.