Study Of Adsorption Properties Of Diatomite And Its Preparation For Silica

Diatomite has many unique physical and chemical properties,such as low density,low rigidity,highly porous structure,large surface area, and strong adsorptive capability,so it is widely used in industrial production.Diatomite resource is rich in Shengzhou,Zhejiang Province, the reserves are about two hundred million tons in Puyi and Puqiao area.At present,Shengzhou diatomite is mostly used as filter-aid and insulation materials.Research on using Shengzhou diatomite for functional filler and absorption materials are blank.Though Study on diatomite at home and abroad is universal,the diatom species,ore grade and impurity content are different in diatomite mine in different regions, so the adsorption properties and purification must be different.The content of SiO₂ in Shengzhou diatomite is lower than others inside, generic purifications may not be effective.Therefore,it is a valuable investigation in academe and application to seek after the adsorption properties of Shengzhou diatomite and its preparation for silica.The investigations indicate the following. 1.The diatomite adsorbing process for methylene and Cr(Ⅵ) can be divided into two stages,fast and slow.Diatomite adsorption for methylene and Cr(Ⅵ) is mainly a chemical adsorption and a secondary chemical reaction.Absorption time,the amount of soil and solution,and pH value have influence on the adsorption.When solution pH=8,the removal of methylene is at the maximum rate,and when pH=2,the removal of Cr(Ⅵ) is at the maximum rate.The adsorption properties of diatomite can be improved by using alkali dissolution,but it has no effect by pickling and calcination.Models of the adsorption match the Langmuir and the Freundlich adsorption isotherms well.The adsorption capacity of diatomite and alkali modified soil are 44.7mg/g and 63.7mg/g,and the Freundlich adsorption isotherms are q=40.4C^0.67 andq=42.1C^0.26.After alkali modified,the saturation adsorption capacity has been increased.2.A little SiO₂ can been prepared by using heating alkali dissolution form diatomite.Digestion rate of SiO₂ reaches 32.67%,the conditions follow:quantity ratio of NaOH and diatomite is 5:2,ratio of liquid and solid is 2:1,temperature is 95-100℃and time is 8h.3.The optimum adsorptive conditions of high temperature alkali dissolution can be obtained:quantity ratio of NaOH and diatomite is 1:1,temperature is 450℃,time is 2h,digestion rate of SiO₂ reaches 75.51%.The SiO₂ content is 91.9%,loss on heating is 4.7%,loss on ignition is 6.4%,Fe₂O₃ content is 0.07%and the dibutylphalate absorption number is 2.1cm³/g in the sample.4.The optimum adsorptive conditions of pickling can be obtained: pickling time is 24h,acid dosage is twice as much as the one in theory, the ratio of liquid and solid is 3.3,pickling temperature is 95-100℃, calcination temperature is 700℃and time is 2h,the SiO₂ content can reach 73.8%.The method of pickling can remove a part of impurity,but the clay removel is not evidence.the physical beneficiation and chemical purification must be combined to get a better effect.