Experimental and theoretical studies on the removal mechanism of formaldehyde from water by mesoporous calcium silicate

Most porous materials with high specific surface area and diverse internal structures possess good adsorption ability. In this work, a tremella-like mesoporous calcium silicate hydrate (CSH) with high adsorption capacity was successfully prepared via a facile hydrothermal method. The adsorption effect and adsorption mechanism of the as-prepared calcium silicate hydrate (AP-CSH) towards formaldehyde from water were investigated systematically. Results indicate that AP-CSH has high Ca/Si ratio (1.95), large specific surface area (122.83 m(2) g(-1)) and exhibits excellent adsorption capacity. The results of batch adsorption experiments show that AP-CSH can remove formaldehyde from water rapidly and effectively with the maximum removal efficiency of 98.94%. The adsorption process agrees well with the pseudo-second-order and Freundlich isotherm model. Furthermore, regeneration can be achieved by simply immersing AP-CSH in absolute ethanol and the removal efficiency can still reach about 99.50% after five cycles. The adsorption mechanism was also studied by experimental analyses and molecular dynamics simulation. Both experimental results and theoretical simulation support that formaldehyde adsorption over AP-CSH belongs to chemical adsorption.