A simple method to valorize silica sludges into sustainable coatings for indoor humidity buffering

Abstract

In this study, the production of indoor humidity-buffering coatings (IHC-s) from recycling waste silica sludges by using a room-temperature sol-gel method which is a simple and energy-efficient route is reported. The properties of these IHC-s are identified by scanning electron microscope, X-ray diffraction, X-ray fluorescence spectrometer, laser particle size analyzer, N2 adsorption-desorption isotherms and toxicity characteristic leaching procedure (TCLP). The moisture adsorption-desorption tests show that the IHC-s have moisture buffering values of ca. 270–316 g m− 2 and moisture contents of 23.6–26.7% in the range of 50–90% relative humidity (RH). Furthermore, the humidity buffering capacities, moisture adsorption-desorption rate and stability are significantly superior to commercially available coatings in the range of 50–75% RH. The enhancement may be due to the formation of porous structure in the coatings via the dispersed waste silica sludges and gypsum which transformed from bassanite by self-assembly process. Most importantly, the prepared IHC-s show surpassing antimicrobial efficacy (> 99.99%) and no detectable leaching heavy metals based on TCLP tests, which provides an economic and environmental-friendly route for recovering and valorizing industrial wastes.