Modification of a MoS2 composite membrane using nano-silica for high-efficiency dye separation

Abstract

Two-dimensional (2D) layered MoS₂ membrane has a unique pore structure, adjustable interlayer spacing and excellent transmission performance, which has wide-ranging and excellent application prospects for water treatment. However, the MoS₂ membrane exhibits a narrow interlayer height, which can only accommodate one layer of water molecules, causing low water permeation and flux. In this work, a MoS₂/SiO₂ composite membrane with regular transport channels was prepared by the vacuum-assisted self-assembly (VASA) process using the intercalation of nano-silica (SiO₂) nanoparticles. The resulting membrane showed an increase in interlayer widths from 0.61 nm to 0.69 nm. The MoS₂/SiO₂ composite membrane featured a high-efficiency dye separation performance and aqueous stability as the mass ratio of MoS₂/SiO₂ was 2.5, and the water permeance flux could reach 979 L m⁻² h⁻¹ bar⁻¹, with a rejection of 100% for Evans blue (EB), methyl blue (MB) and neutral red (NR) and a rejection of over 98% for rhodamine B (RhB). MoS₂ membranes decorated by SiO₂ nanosheet nanoparticles could effectively achieve precision regulation of interlayer spacings and hold the channel order of MoS₂ laminates. In addition, the rejection rate of the composite membrane remained 100% after remaining immersed in strong oxidizing acid for up to 60 days, which showed their stability toward strong acid and oxidative environments. This work suggests that an interlayer manipulation strategy in 2D laminar membranes could improve membrane performance for wastewater treatment and other separations.