Synthesis of mixed-phase uniformly infiltrated SBA-3-like in SBA-15 bimodal mesoporous silica from rice husk ash

The mixed-phase bimodal mesoporous silicas (BMS) were simply synthesized via sol–gel technique using rice husk ash-derived sodium silicate as a silica source, and Pluronic P123 and cetyltrimethyl ammonium bromide (CTAB) as the pore structure-directing agents. The gel solution composition in the synthesis process was based on SiO2:Pluronic P123:CTAB:HCl:H2O molar ratio of 1:0.088:0.088:4:200. The effect of mixing sequences of starting materials on BMS structures was investigated. The phase separation among SBA-15, SBA-3-like porous silica and xerogel was found when the gel solutions of SBA-15 and SBA-3-like were prepared separately in the primary stage, whereas the mixed-phase uniformly infiltrated SBA-3-like in SBA-15 bimodal porous silica was successfully synthesized when CTAB was added into the SBA-15 gel solution and the secondary micelle structure was formed inside the primary SBA-15 framework.