Preparation and water adsorption performance of attapulgite based calcium chloride composite adsorbents for cooling and air conditioning applications

A series of attapulgite based CaCl₂ composite adsorbents (AT-CaCl₂) were prepared, and their water adsorption performances were determined through static weighting method. The effects of preparation method, calcination temperature and time and calcium chloride content on the water adsorption performance of the prepared AT-CaCl₂ were investigated, and the preparation conditions were optimized. The prepared composite adsorbents were characterized by X-ray diffraction and low temperature N₂ adsorption. The results show that, among the preparation conditions, the calcination temperature plays the dominant role, and the optimum preparation conditions found are as follows: Adopting the dissolution-mixing method, using calcination temperature of 300°C and calcination time of 2 h. At low relative humidity (RH < 20%), both attapulgite structure and chloride content play prime roles in water adsorption of the AT-CaCl₂, while at higher relative humidity (RH > 30%), the water adsorption performance of AT-CaCl₂ depends strongly on its chloride content. At high relative humidity (RH = 80%), water loading of AT-CaCl₂ with 20% CaCl₂ can be as high as 0.65 kg·kg^-1, while at the relative humidity of 20%, the loading is about 0.30 kg·kg^-1. The prepared composite adsorpbent AT-CaCl₂ can be effectively regenerated and reused.