Coupling of titania with multiwall carbon nanotubes for decomposition of gas-phase pollutants under simulated indoor conditions

Abstract

This study synthesized multiwall carbon nanotube (MWNT)–titania (TiO2) composites and examined their characteristics and photocatalytic performance for the cleaning of gas-phase benzene, toluene, ethyl benzene, and o-xylene (BTEX) under simulated indoor conditions. Optical and spectral surveys of the as-synthesized composite confirmed that the TiO2 nanoparticles were bound intimately to the MWNT networks. The photocatalytic performance was evaluated using an annular-type reactor inner-coated with MWNT–TiO2 or Degussa P25 TiO2. The composite revealed gas removal ability superior to that of stand-alone TiO2. This composite was also less affected by humidity during toluene decomposition compared to the previous result obtained from a stand-alone TiO2. Unlike another previous result obtained from the TiO2, the performance of the composite was not affected by changes in input concentration (IC) within a simulated indoor air quality range (0.1–1.0 ppm) but it decreased significantly when the IC was increased to 5 and 10 ppm. As the flow rate was decreased from 4.0 to 1.0 L min−1, the average efficiency for the target compounds increased to 95% or ∼100%. The MWNT–TiO2 composite could be applied effectively to the decomposition for BTEX under certain simulated indoor conditions. Implications: Unlike water applications, there are few reports of gas-phase applications of multiwall carbon nanotubes (MWCNT)–TiO2 composites. This study found that MWCNT–TiO2 composites showed performance in the removal of toxic gaseous aromatic superior to that of stand-alone TiO2. In addition, the pollutant degradation efficiency of the composite was less affected by humidity than for a stand-alone TiO2 unit within a simulated indoor relative humidity range. Moreover, unlike the TiO2 unit, the composite's performance was not affected by variations in the input concentrations within the simulated indoor air quality (IAQ) range. In addition, the decomposition efficiencies increased to 100% with decreasing flow rate.