| Diatomite is natural amorphous silica engendered by deposition of diatom skeleton. For its high porosity with strong adsorbability and excellent thermal resistance, diatomite is broadly used for filter aid, catalytic support, adsorbent, functional filler and insulation material.Diatomite as pure as possible is preferable when it is used for high value-added products such as filter aid and functional filler etc. Accordingly, studies on purification of raw diatomite are crucial. At present, the main technique taken by enterprise in our country is chemical method in which high concentration acid solution process is applied. Nevertheless, disadvantages of the method are obvious: high concentration acid will erode equipment and cause environment pollution. On the other hand, clay minerals existed in raw diatomite will be transformed to amorphous SiC>2 when they are dissolved by acid, but this kind of amorphous SiOi does not possess porous structure analogical to diatom skeleton. Thus, how to produce refined diatomite by physical purification process without or with less acid, is a very important problem to resolve. However, the efficiency of physical purification process applied in our country is commonly low. In this work, methods for improving this situation were studied.In recent years, the diatomite's functional applications which including using in novel biological support, pharmic carrier, chromatogram support, adsorbent and functional filler are becoming the most promising aspect of its applications. A great deal of works related to interface reaction between diatomite and adsorbed molecules/ions ones need to be developed. It is a pity that pertinent studies carried out are far from enough in our country. In this work, some basic problems in interface reaction study, i.e. type, origin and property of main reactive site including hydroxyl groups and acid sites, are studied. And methods developed to regulate the surface acidity are discussed.Central content of this work and corresponding fruits are listed as follows:1) Low efficiency of physical purification process result from incomplete dispersion and analogical precipitation behavior between clay and diatom particles. By experiments on monominerals and diatomite samples, the author worked out stirring-ultrasonic dispersion and selective flocculation-precipitation process to resolve the above two problems. Refined diatomite samples by applying this purification process were ranked as grade I and the output rate was above 50%.2) DRIFT and MAS NMR Spectroscopy were used to detect the structure of surface hydroxyl species. The quantity of different hydroxyl groups was estimated bytitration methods and the spectroscopy technique. A condensation-dehydration mechanism of surface hydroxyl species and adsorbed water molecules under calcination conditions was set up.3) The origin of diatomite surface acidity was discussed according to results of ammonia-DRIFT, pyridine-Raman and in situ pyridine-IR spectroscopy. And varieties of acidity with conditions of thermal treatment were elucidated in detail.4) Effective methods for acidity regulation were developed. The relevant measures of acidity regulation were discussed.Innovations of this work include:1 ) Developed two new methods including stirring-ultrasonic dispersion and selective flocculation-precipitation process, to resolve the problems of low efficiency of physical purification method. Applied this novel purification process, raw diatomite samples ranked as grade two or three were purified as samples ranked as grade one without acid-treated process. And the output rate was relatively high.2) Taken the lead in studying the main reactive site which include hydroxyl groups and acid sites on diatomite surface. Discussed the quantity, type, and structure of hydroxyl groups and the condensation behaviors of them in detail, and provided the corresponding evidences of spectroscopic analysis.3 ) Analyzed the origin of surface acidity by abundant data of spect...
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