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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