GEOLOGIJA 33, 447-459 (1990), Ljubljana UDK 553.578(560) = 20 Determination of the properties of various diatomite deposits within Aegean Region of Turkey Uner Ipekoglu Dokuz Eylul University, Faculty of Engineering and Architecture, Dept. of Mining Engineering, Bornova, Izmir, Turkey Zeliha Mete Dokuz Eylul University, Faculty of Education, Dept. of Chemistry, Buca, Izmir, Turkey Abstract Properties of diatomite in general have been outlined, location and reserves of the related deposits in Turkey are given. The results of mineralogical studies, chemical and physical analysis which have been carried out on various samples are tabulated. From the results of these findings possible application areas have been suggested. Introduction Diatomite in its natural state is a soft rocklike material consisting esentially of the skeletal remains of a variety of singlecelled microscopic plants known as diatoms. They are generally amorphous, hydrated or opaline silica, SÌO2 x n. H2O, with various amounts of impurities such as silica sand, clay minerals, metal salts and organic matter. Because of these contaminants, silica content may range from 58 to 90% of the dry product. As mined, diatomite may contain from 10 to 60% of free water. Size of diatoms varies between 20 to 200 microns. The most important properties of diatomite are its porosity (80-85%), low density (1.95 to 2.3g/cm3) and whiteness (as high as 96). The color of diatomite changes depending on the impurities present in the sand. For example an increase in the amount of organic matter causes the color to change from white to brown or even to green. Diatomite is not dissolved in acidic solutions except in hydrofluoric acid but it dissolves in concentrated alkaline soluti- ons. The hardness of the diatom skeleton is between 4-6.5 on the Moh's scale the same as opaline silica. Heat conductivity of diatomite is low; 0.08-0.1-0.11 kcal/m.°C.h at temperatures of 300, 800-1200°C respectively. Its melting point is PCE 8-33 and the pressure resistance is between 3-18kg/cm2. Because of its unique and desirable properties mentioned above, diatomite is 448 Uner Ipekoglu & Zeliha Mete a superior material to many alternative substances in many industrial applications. The widest use of processed diatomite is as a filter aid for separation of suspended solids from fluids. About 50% of all processed diatomite is channeled into this application. Other important uses include soft abrasives, industrial fillers, lightwe- ight aggregates and insulation. As a filler and extender it is used in paint, asphalt products, paper and plastics. Other uses include catalysts in petroleum refining, hydrogénation of oils, insecticide carriers, anticaking agents for fertilizers and explosives, soil conditioner and as an additive in cement (Kadey, 1983). Processing of diatomite involves a series of basic steps developed primarily to take advantage of the unique characteristics of the commodity for its various applications, such as filter aids, fillers and insulation. The major processed diatomite products are powders and aggregates of variable sizes and grades that have been uncalcined, straight-calcined or flux-calcined. Processing of uncalcined or »natural« grade diatomite simply comprises the drying and crushing of crude ore to reduce the high moisture content. Further size reduction and removal of water is usually accomplished by a blower-hammer mill in combination with a pneumatic feed and discharge system to suspend the particles. The suspended particles and impurities are separated and removed through a series of cyclone classifiers. The variously sized products are then collected in a baghouse for market preparation, principally for fillers and other uses than filter aids. For filtration uses »natural« grade diatomite is calcined by heat treatment in a rotary kiln at a temperature of about 1000°C for the following purposes: - To remove any organic matter or contained water - To convert some impurities into a fused slag - To fuse broken diatoms into a fritted product The resultant straight-calcined powder is of light weight, cream to slightly pink color, chemically inert, and from which the chemically combined water has been removed. Its main use is as a filter aid, on liquids with larger suspended particles where medium flow rates are required. For filtering that requires faster flow rates, up to 10 % of alkaline salt (NaCl + NaOH or КагСОг) may be added to the diatomite in calcining, and it sinters the diatomite particles, increasing the particle size therefore increasing the speed of filtration with satisfactory classification (Weiss, 1985). Location and reserves of diatomite deposits in Turkey Deposits occur mainly in three different regions in Turkey; a - Central Anatolian deposits b - Eastern Anatolian deposits c - Western Anatolian (Aegean region) deposits Location, known and estimated reserve potential of Turkish diatomite deposits are shown in figure 1. (Private communication with the authorities of MTA - Mineral Research and Exploration Organization - and Turkish Sugar Industries General Management, 1988). The total consumption of natural-grade and processed diatomite according to the figures obtained in 1980 is given in table 1 (Devlet, 1979). Turkey's demand for natural-grade diatomite is met by domestic resources. Processed diatomite is imported except for the sugar industry which produces its own diatomite in the plant which started with operation in 1982. Determination of the properties of various diatomite deposits... 449 M 'S o a ш ТЗ <и 6 O 2 ^ JS t/3 iS l-l 3 H Ч-1 0 V)