Study On Preparation And Performance Of Diatomite-based Humidity Controlling Materials

The text has chosen crude diatomite with good performance and got materials with good adsorption/desorption capabilities through scrubbing, vitriolling and activating with inorganic salt. The Pore structure is tested by BET and BJH. The microcosmic appearance is observed by SEM and TEM. The moisture adsorption/desorption properties and the absorption/desorption isotherms are tested by static absorption method, which can characterize humidity controlling abilities.The text has studied the best parameters of purification methods on the pore structure in orthogonal experiment. 1) The consistence of sulfuric acid is 60%, and the ratio of liquid and solid is 2:1, and the reaction time and temperature are respectively 90 min and 100℃. The specific surface area of vitriolling diatomite is 26.1 m²/g, and the content of SiO₂ is 89.24%, and the amount of humidity absorption closes to 13%. 2) The consistence of sodium hydroxide is 5%, and the ratio of liquid and solid is 6:1, and the reaction time and temperature are 45 min and 60℃. The specific surface area of alkalifying diatomite is 32.9m²/g, and the content of SiO₂ is 84.34%, the amount of humidity absorption is 13.5%. 3) Heating rate is 5℃/min, and the calcination temperature and holding time are 500℃and 1h. The specific surface area of calcining diatomite goes down to 15.654 m²/g, while the content of SiO₂ is 90.26%, and the amount of humidity absorption decreases to 8%.The text has fixed the best parameters of activating by the inorganic salt on its hygroscopicity in orthogonal experiment. The consistence of inorganic salt is 30%, and the ratio of liquid and solid is 5:1, the reaction time and temperature is 90 min and 60℃, yet working environment selects the right inorganic salt. The amounts of adsorption and desorption of inorganic salts activated diatomite are both improved. The maximum absorption amount can be up to 102%, while the maximum desorption be 35%. The hydration of inorganic salt and the pore structure and surface hydroxyl of diatomite are principles of moisture absorption of the activated diatomite. Inorganic salts fill in or wrap on the pore surface of diatomite, and preferring to fill in the pores of diameter 40-80nm.