Calcination Modification, Aid Filtration Adsorption Properties And Mechanism Of Linjiang Diatomite

Diatomite is a significant non-metal ore. The application of diatomite in filter aids, adsorbent and etc is very extensive because of its advanced microporous and high chemical resistance. Eighty percents of diatomite products are needed to modify by calcining in the preparation processing. So the study was focus on the problems in calcination modification procedure with Linjiang diatomite, the reserve of which is abundant. The paper is meaningful to the comprehensive development and added value utilization of the resources both in theoretical and practical aspects.The effects of calcination modification technological conditions on properties of filter aids, the effects of modified temperature, flux and plasticizer on structure intensity and adsorption ability of diatomite adsorbing ceramsite, the effects of modification temperature and calcination with flux on diatomite properties were explored. The systematic representation and mechanism analysis of preparation procedure and aid filtration adsorption properties of the materials were conducted by XRD, FTIR, SEM, BET and etc. The specific conclusions are listing below:(1) Calcination modification applied to filter aidsThe reducing atmosphere of calcination modification could restain the combustion of organic matter and avoid the excessive fusing of diatom, and then the filter aids with better filtration properties could be obtained. The contents of soluble iron ion in beer filtration could be reduced by lowering the iron content of raw diatomite or adding water after calcination modification. Separating the fine particles by wet classification after calcination modification could reduce the content of respirable crystal silica. The study on mechansim of precoat filtration showed that the filtration of beer by diatomite filter aids was mainly depended on surface intercept, assistant with depth intercept and adsorption. The adsorption of beer impurities by diatomite was an exothermic, spontaneous and physical adsorption processing.(2) Calcination modification applied to adsorbing ceramsiteThe increasing of modified temperature was beneficial to the structure intensity, but the silicon hydroxyl was destroyed and the adsorption ability decreased. The flux was benefical to the structure intensity when the modified temperature was higher than 600 ?. The silicate cement was the best plasticizer. The drop times before damaged and lost in adsorption of ceramsite was 49 and 1.96%, respectively, which was prepared with silicate cement. The research of adsorption of X-GRL by diatomite showed that the adsorption was an endothermic, spontaneous and physical adsorption processing. The main driving forces of the physical adsorption of X-GRL on the diatomite were electrostatic attraction and Van der Waals forces.(3) Effects of modification temperature on diatomite propertiesThe particles were bigger with the increasing of modified temperature because the diatom fused. The highest specific surface area, cumulative pore volume and average pore diameter can be gotten at 400 ? without flux. The respirable fraction for crystalline silica was higher than 1% when the temperature was higher than 1000 ? without flux or higher than 800 ? with flux, which was higher than the value of American standard and harmful to human health.In calcination modification without flux, the quartz converted to tridymite at the temperature higher than 900 ?, and the opal consisted with crystallite crystobalite turned to crystobalite at the temperature higher than 1000 ?. The flux could reduce the transformation temperature of quartz to tridymite and opal to crystobalite about 200 ?, and made the tridymite convert to crystobalite at 1100 ?. The metal ion in flux break down firstly Si-O-Si bonds and make it recombined. The metal ion can balance the electrocalence at the edge of the mesh crystal structure, and make the structure stable, so the flux can lower the transformation temperature of the process with the Si-O broken. Since the atomic radius of Na+ is smaller than that of K+?Rb+ and Cs+, the probability of entering into the structure is higher. Thus, the fluxing ability of flux with Na+ is higher.