MWCNT–TiO2–SiO2 nanocomposites possessing the photocatalytic activity in UVA and UVC

• The addition of MWCNT to the TiO2–SiO2 system modifies the nanotubes surface.
• Even a small addition of MWCNT decreases the catalysts’ Eg quantity.
• The application of above 8 wt% CNT in TiO2 promoted the Ph photooxidation.
• k1 values using WB20 and WB40 are nearly twice as large as for WB1.
• MO was removed by the nanocomposites very efficiently both using UV and Vis.

The results of studies on application of TiO2 and SiO2 co-precipitated in the presence of CNT to prepare the nanocomposites CNT–TiO2/SiO2 are presented. Nanocomposites were characterized by a large overall surface area (243–252 m2/g), occurrence of TiO2 in the anatase form (7–8 nm) and reduced band gap energy (from 3.2 eV to 2.2 eV). The studies confirmed the role of CNT as a factor not only increasing the overall surface area of the nanocomposites but also allowing for obtaining the systems of uniform distribution of the crystallites TiO2/SiO2 on their surface and those activated with visible light. Photocatalytic oxidation carried out for 2 h using the nanocomposites resulted in 75% removal of phenol (UVC irradiation) and a complete loss of methyl orange (UVA irradiation). The nanocomposites containing about 8 wt% of CNT were the most active. Removal of the phenol and methyl orange proceeded according to the first order kinetics (k1 for UV decomposition of phenol was 0.4–0.74 × 10−2 min−1, and for Vis removal of methyl orange 2–12 × 10−2 min−1).

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