Nano-structured TiO2–SiO2 pellets were prepared using the
sol–gel method in this study. The TEM image of the sample
revealed that the sample consisted of agglomerates of nanostructured
particles of about few nanometres in size. The sample
has a very porous and non-smooth surface. Toluene was used as
an indicator of VOCs in the experiments. The initial concentrations
of untreated gas were measured on line as 1149 mg/m3
(300 ppm). The TiO2 pellets used had a surface area of 50m2/g.
When the UV irradiation and feeding gas was continuous, the
destruction efficiency of about 25%was achieved over the period
of 20 h. Once the systemwas operated at adsorption/regeneration
mode, a higher removal efficiency of about 55% was maintained.
This supported that it is possible to use TiO2–SiO2 as
either adsorbent or photocatalyst. TiO2–SiO2 pellets with different
surface areas were used in the experiments, while the
initial toluene concentration and other operational conditions
were kept constant. It was found that the TiO2–SiO2 pellets
with higher surface area (421.1m2/g) achieved 100% conversion
efficiency for a substantial period of time (4 h), whereas the
catalyst with low surface area only had a very brief period of
100% degradation efficiency. The higher surface area indicates
a more porous material, and higher adsorption capacity, and
leads to higher conversion efficiency. This is confirmed by calculated
kinetic rate constants.Within the regeneration limits, the
adsorption enhanced catalyst can adsorb and then destruct more