Multifunctional solar wall for dehumidification, heating and removal of formaldehyde: Part 1. System description, preparation and performance of SiO2/TiO2 adsorbent

Abstract

This article proposes a novel multifunctional solar wall that can realize heating and removal of formaldehyde in winter and dehumidification and removal of formaldehyde in summer. Multifunctional materials focusing on the dehumidification and the removal of low-concentration indoor gaseous contaminant simultaneously are of great interest for the improvement of building environment and energy conservation in building. SiO2/TiO2 composite adsorbents with different TiO2 content for the adsorption of formaldehyde and dehumidification were prepared by the sol–gel method. The porous properties of the composite adsorbents were investigated by ASAP2010 volumetric adsorption analyzer. The water vapour adsorption isotherms at 25 °C and breakthrough curves of formaldehyde at typical indoor pollutant concentrations i.e. 0.7 ppm and 1.4 ppm, respectively were measured. The kinetic adsorption curves of water vapour and formaldehyde on composite adsorbents were measured and linear driving force (LDF) model was applied. Also the kinetic adsorption rate constants obtained by the fittings of the kinetic adsorption curves based on LDF model were analyzed. Results showed that composite adsorbents had excellent water vapour adsorption capacity under the low and medium humidity compared with commercial silica gel. The introduction of TiO2 increased the polarity of composite adsorbents. And composite adsorbent with a certain amount of TiO2 (SiO2: TiO2 = 90: 10, mole ratio) possessed high kinetic adsorption rate constant under the low relative humidity. Furthermore, the introduction of TiO2 improved formaldehyde adsorption capacity under typical indoor concentration levels, which suggested that composite adsorbents were efficient in capturing the trace amount of indoor formaldehyde.