Template-free preparation of humidity self-regulating silica-based mesoporous oxide from volcanic ash

In this work, a silica-based mesoporous oxide (SMO) was directly fabricated via a template-free method using the abundant and inexpensive volcanic ash as raw material. By alkali hydrothermal activation and acid hydrothermal etching of volcanic ash, the SMO with large mesopore size (7.94 nm), high specific surface area (459.5 m 2 /g), and total pore volume of 1.05 cm 3 /g was produced. The main ingredient of SMO is amorphous microporous silica. The structural evolutions of the mesoporous materials were revealed by X-ray powder diffraction, scanning electron microscope, Fourier transform infrared spectrometry, N 2 adsorption/desorption, and transmission electron microscopy techniques. The as-prepared SMO possessed excellent adsorption of water vapor as high as 616.0 g/m 2 at the relative humidity ranging from 33 to 75%. This SMO provides a platform for preparing high performance template-freely humidity self-regulating material. This figure shows that silica-based mesoporous oxide (SMO) quickly adsorbs moisture at RH = 75% and reaches to 616.0 g/m 2 , and then the adsorbed water releases at 33% RH. These results suggest SMO have an excellent humidity self-regulating function in the RH ranging from 33 to 75%.