Synthesis and characterization of novel SiO2 and TiO2 co-pillared montmorillonite composite for adsorption and photocatalytic degradation of hydrophobic organic pollutants in water

Abstract

A series of SiO2 and TiO2 co-pillared montmorillonite photocatalysts with excellent adsorption capacity and high photocatalytic activity were synthesized via a sol–gel method by pillaring both SiO2 and TiO2 mixed sol into sodium montmorillonite. Various material characterization techniques such as powder X-ray diffraction (XRD), nitrogen adsorption/desorption isotherms and scanning electron microscopy (SEM) were used to examine the pillared montmorillonites. 2,4,6-trichlorophenol, a typical hydrophobic organic pollutant, was used as a model pollutant to evaluate the adsorption capacity and photocatalytic activity of the prepared co-pillared montmorillonites. The experimental results showed that large SiO2 content in the pillared montmorillonite was in favor of large adsorption capacity, while large TiO2 content in the co-pillared montmorillonite was beneficial for the high photocatalytic activity, and the highest photocatalytic activity was obtained for the prepared co-pillared montmorillonite with a SiO2/TiO2 molar ratio of 1:2. Additionally, nine intermediates including 2,4-dichlorophenol, 2-chloro-1,5-diphenol, 1,3,7-trichlorodibenzo-p-dioxin, 2,6-dichlorodibenzo-p-dioxin, hexadiene diacid, butyl alkyd, oxalic acid, phloroglucinol and diphenol were detected, and a photocatalytic degradation mechanism of TCP was tentatively proposed.