A triply synergistic method for palygorskite activation to effectively impregnate phase change materials (PCMs) for thermal energy storage

Abstract Palygorskite (Pal) is considered as an excellent adsorption material due to its unique layered, porous and tubular structure. However, the adsorption ability of raw Pal is limited, and further modification is necessary. In this paper, we employed a triply synergistic method to activate Pal, including wet grinding, hot acid etching and heat expanding (Pal-g-a-h). The properties of Pal-g-a-h and the Pal-g-a-h-based composite phase change material (Pal-g-a-h/PEG) were compared with those of Pals activated solely by heat (Pal-h) or acid (Pal-a) and their corresponding phase change materials (Pal-h/PEG, Pal-a/PEG) through SEM, TEM, BET, FTIR, DSC,TG, and thermal conductivity, regulation and cycling measurements. The SEM, TEM and BET results manifested that the dispersity, pore volume / size and specific surface area were significantly improved by the triply synergistic activation. The more formation of Si O in Pal-g-a-h confirmed by FTIR favored the enhanced adsorption and fixation of PEG through the hydrogen bond. Compared with the single activation process, wet grinding-acid-heat method enabled Pal-g-a-h/PEG to possess the best thermal performance, including thermal storage capacity (△Hm = 82.48 J/g), stability, conductivity (0.31 W/mK) and reliability. The research on the triply synergistic activation helps broaden the adsorption ability of porous materials to fabricate more effective phase change materials for energy storage and retrieval especially in the architectural field.