Removal of volatile organic compounds from air using supported ionic liquid membrane containing ultraviolet-visible light-driven Nd-TiO2 nanoparticles

Abstract

Volatile organic compounds (VOCs) with toxicity properties discharged from industrial emissions and combustion engines threaten human health and cause environmental problems. Therefore, it is important to develop technologies to remove VOCs from air. In this study, the performance of Nd (neodymium) -TiO2 nanoparticles embedded in a supported ionic liquid membrane (SILM) for removal of VOCs from air was investigated. Aiming at functionalizing the ionic liquid membrane with photocatalytic capability, we developed a facile and effective approach for the removal of VOCs by coupling highly efficient photocatalysts with the SILM. Nd-TiO2 nanoparticles, which are ultraviolet-visible (UV–Vis) light-driven photocatalysts, were prepared by sol-gel and immersed in the SILM for use as a photocatalytic membrane-based reactor. The gaseous VOCs tested were toluene, acetone, chloroform, benzene, and xylene. We confirmed that at a loading of 50 wt% Nd-TiO2 nanoparticles (1 wt% Nd content) and 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIm]PF6) as SILM ([HMIm]PF6/Nd-TiO2 SILM), the as-prepared photocatalytic membrane-based reactor exhibited higher removal efficiency of VOCs from air (60~80% removal after 10 h) under UV–Vis light illumination than individual SILM or photocatalytic systems. Effluent gas analysis revealed that 25–55% of VOCs was decomposed and mineralized in the photocatalytic membrane reactor, which exhibited higher VOCs removal efficiency than membrane separation. These results indicate that the photocatalytic membrane-based reactor containing Nd-TiO2 nanoparticles and SILM designed in this study is highly active and stable. This study on [HMIm]PF6/Nd-TiO2 SILM was initiated to couple membrane separation with photocatalytic degradation of gaseous VOCs and can serve as a promising way for eliminating harmful VOCs with low concentration from air.