The Silylation Modification Of Diatomite And Its Influence On The Cu(Ⅱ) Adsorption Performance

Diatomite, known as inorganic non-metallic mineral material engendered by deposition of diatom shell. The primary inorganic component of diatom shell is a sort of biogenic amorphous silica. For its unique macroporous structure on the surface, diatomite is widely used for filter aid, catalytic support and adsorbent. However, due to the small diameter of environmental pollutants such as heavy metal ions, it is difficult to filter through the diatom shell besides the silanols on the surface are mostly"shielded"by water molecules. Therefore, the copper ion adsorption capacity is not obvious. Accordingly, it is used to improved the adsorption ability of diatom shell by silylation modification on the surface of diatomite.In this work, diatomite was modified by organosilane-grafted, in order to prepare silicon materials with high adsorption capacity of copper ion. In addition, the surface silylation impact of diatomite pretreated with different temperature and its influences in the application for adsorption were studied. The influences of pretreatment temperature on the surface modification of diatomite was investigated,and find the appropriate pretreatment temperature for organosliane grafting. Central conclusions of this work and corresponding fruits are listed as follows:(1) Verify the influence of thermal pretreatment on the surface structure and properties.The mineral structure of diatomaceous opal does not change with the temperature lower than 1100oC. At 800oC, the porous structure of diatomite is destroyed; At 600oC, the physisorbed water on the surface of diatomite is almost dehydrated. At 700oC, the capping water that H-boned with the surface silanols is removed;when the pretreatment temperature is higher than 700oC,the surface silanols of diatomite are removed,the surface adsorption water and silanols density is 4.31 mmol/g and 0.82 mmol/g, respectively.(2) Find the appropriate pretreatment temperature for silylation reaction of diatomite.The crystalline structure of diatomite does not change after APTES modification, there is condensation reaction of APTES on the surface of diatomite, and the pretreatment temperature is crucial to the amount of grafted APTES on diatomite, consequently, the ideal pretreatment temperature is 800oC.(3) Evaluate the adsorption capacity of copper ions by silylated diatomite. The copper ions adsorption ability of diatomite is improved after modified, and the adsorption capacity is 16.8 times higher than before. The copper ions adsorption by diatomite is chemical adsorption process, and an equilibrated adsorption can be got within 120 minutes and better adsorption effect will come true with pH value between 4~7.The research about diatomite could be providing useful information for application of heavy metal pollutants, metal recovery and other fields. In addition, the study could help improve the utilization level of diatomite.