Efficient adsorption of trace formaldehyde by polyaniline/TiO₂ composite at room temperature and mechanism investigation

Formaldehyde is a common indoor environmental pollutant, which poses a great harm to human body. In this study, the adsorption behavior of a novel polyaniline/TiO₂ (PANI/TiO₂) for formaldehyde from air at room temperature, comparing to that of activated carbon and glass beads, was investigated, and the mechanism was interpreted in details. Polyaniline/TiO₂ exhibited enhanced adsorption capacity of 0.67 mg g⁻¹ for formaldehyde acquired from the Langmuir equation, which was higher than that of commercially used activated carbon of 0.50 mg g⁻¹. While polyaniline/TiO₂ could also be stably recycled by using simple acid-base treatment. Moreover, the initial adsorption rate order of polyaniline/TiO₂>activated carbon > glass beads was acquired from kinetic study, confirming the superiority in the formaldehyde removal of our polyaniline/TiO₂. Confirmed by adsorption isotherm study and various characterization experiments including X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FT-IR), Scanning electron microscope(SEM) and N₂ adsorption-desorption isotherm, the adsorption of formaldehyde on to polyaniline/TiO₂ may be through a chemical adsorption, in which the amine and imine groups in the polyaniline chain play important roles in the interaction between polyaniline/TiO₂ composite and formaldehyde, and the formaldehyde may form as doping groups doped onto the polyaniline/TiO₂. This contributes to the advanced adsorption affinity and capacity of polyaniline towards the formaldehyde even in a trace initial concentration, outperforming the commercially available activated carbon and glass beads very much. These novel properties allow polyaniline/TiO₂ to be applied as an advanced formaldehyde scavenger in next generation to protect human being from the danger of formaldehyde, challenging present commercially available formaldehyde adsorbents greatly.