Investigations of the applicability of Tokat-Reşadiye region bentonites in wall tile bodies

A ceramic is identified as an inorganic nonmetallic high temperature fired soil; it is a decoration product which is used for coating the inner surfaces, exterior surfaces and floors of the buildings. It is acquired from the proportional mixture of clay, kaoline, quartz, feldspar etc. which are gained from nature. These materials are made paste and pressed and fired above 1100oC. In the history of ceramic, first ceramic has been produced in B.C. 6000, in Anatolia. After 8000 years, the ceramic parts which was picked up from the excavation in Catalhoyuk are still exist without any breakdown. Turkish porcelain and ceramic art has a seat between the Turkish arts. In 16. Century, Turkish porcelain and ceramic art reached its peak point with the continuous improvement of technical and artistic aspect. In the 16thcentury, Iznik and Kütahya porcelain pastes consisted of bentonite that contains silica, glass frit and 80% of montmorillonite. Gradual depletion of the known raw materials reserves of the world leads man to explore new mineral deposits and to evaluate better the known ones. Bentonite is one of the most important and abundant clays of Turkey. Lower cost of bentonite in comparison to other raw materials for various usage increases demand for it. Therefore, discovery of new and better quality deposits and carrying out of research to increase the quality of the known deposits are important as their contribution to the Turkish economies will be large. Bentonite often contains 80% montmorillonite. Bentonite is used in a wide range of applications including drilling mud, bleaching earth, water and solvent based rheological additives, cat litter, desiccant clay, and animal feed additive. Due to high viscosity and swelling and low filtration loss, (Na–Ca)-bentonites are in high demand in commercial applications. It is commonly known that even good quality sodium bentonites may not meet the required standards for drilling muds as drilling-fluid additives in their natural forms. Their main functions are to viscosify the mud and reduce fluid loss to the formation. By alkali activation or by introducing some polymer additives, it is possible to upgrade some (Na, Ca)-bentonites and even calcium bentonites to meet the API or TS EN ISO 13500 (30 cP minimum viscosity at 600 rpm; 15 cm3 filtration loses and 22 ml swelling index) standards. Because raw (Na–Ca)-bentonites exhibit high filtration losses and do not develop sufficient viscosity, they cannot meet the above standards and thus require appropriate activation formulations. These activations typically employ various additives such as soda, MgO, and a polymer, usually CMC (carboxyl methyl cellulose). Bentonites which are widely used in controlling the stability of industrial suspensions due to their high cation exchange capacity may be classified as alkaline (Na bentonite), semi alkaline (Na-Ca bentonite), alkaline earth (Ca bentonite). While Na bentonites are used as drilling fluid for their existing technological properties, semi alkaline and alkaline earth bentonites have limited use in this industry. Although reserves of Na bentonites are limited both in our country and in the world, there is unlimited reserves of Na-Ca and Ca bentonites. It is generally difficult to use these bentonites in their natural form in drilling industry because of their average and low swelling capacity, viscosities and high filtration losses. The only way to obtain drilling mud in compliance with the API and TSE standarts is to activate bentonite by adding various additives. Using new technological developments with these type of bentonites, will be highly competitive and highly important for our national economy. The increasing demand of bentonite utilization for advanced material technology and the limited reserves of high quality bentonites push the reserachers and the operators/producers to evaluate the lower quality calcium and mixed bentonites for the replacement of Na-bentonites in use. The technological properties of bentonites, however, can be upgraded by the application of concentrating and alkali activation. Mostly, wet concentration methods such as decantation, hyrocycloning and centrifuging have been applying and water quality and ion type/amount which the water carries becomes more important to controll the further activation process since bentonites carry the releasable and exchangable cations on interlayers which interact with ions in water. Bentonites have a wide range application areas due to their colloidal properties with high plasticity and superior binding characteristics and high swelling capacity in aqueuous and some organic environments. They are components in many commercial products. They are used as the binders for the preparation of casting molds sand and for pelletizing and agglomeration. Bentonites can be classified as sodium bentonite, calcium bentonite and sodium-calcium mixed bentonite. The small addion of bentonites increases the plasticity of different ceramic green bodies and also increases green and dry strength and dry shrinkage. The amount of bentonite added into the ceramic body differ considerably. The main aim of this research project was to evaluate the technological values of bentonite originated from the Tokat-Reşadiye region in Turkey, provided from the Karakaya Bentonite Company, and determine the optimum usage conditions in ceramic industry. Also, the chemical and physical properties, i.e., composition, density, pH value, swelling capacity, watch-glass tests, and acid (HCl) reaction tests of the investigated bentonite of Tokat-Reşadiye region were characterized. Conclusions and recommendations obtained from characterization of ceramic body which is prepared on the basis of a standard ceramic wall tile prescription (61% clay, 24% kaolen, 6% quartz, 9% calcite)are compared with ceramic body with Esan bentonite which is prepared on the basis prescriptionto determine the availability in the ceramic industry and optimal use of Tokat-Reşadiye region. The swelling capacity of Tokat-Reşadiye region bentonite was determined as approximately 18, and the swelling capacity of Tokat-Reşadiye region bentonite was approximately 34. As a result of watch-glass test, both the Tokat-Reşadiye region bentonite and Esan bentonite samples exhibited the swelling behavior, then, star-type splitting. The density and pH value of Tokat-Reşadiye region bentonite were measured as about 2.55 gr/cm3 and 9. The density and pH value of Esan bentonite sample were measured as about 2.51 gr/cm3 and 9.5, respectively.These values are compatible with desired pH value (min 8) for the bentonite used in ceramic industry according to TSE 11136. The value of plasticity of Tokat Reşadiye region bentonite was in the range of 143.52 ± 1.21 %, The value of plasticity of Esan bentonite was in the range of 229.89 ± 1.85 %. The firing shrinkage value of Tokat Reşadiye region bentonite was -2% and this value is not compatible with the specified value of firing shrinkage (25%) in TSE 11136 standard. Even instead of firing shrinkage of fired up to 1100 C bentonite tablets showed growing with increasing temperature. The firing shrinkage value of Esan bentonite was 1.77 % and this value is compatible with the specified value of firing shrinkage in TSE 11136 standard. Indentified by TS 11136 standard bentonite color as suitable for use in the ceramic industry is white. After fired 1100ᵒC,the color of examined Tokat-Reşadiye Region bentonite, coffee and shades of coffee, is not suitable for use in the ceramic industry. After fired 1100ᵒC,the color of examined Esan bentonite, white and shades of white, is suitable for use in the ceramic industry according to TS 11136. Analyzed in terms of chemical properties, Tokat Reşadiye region bentonite involved wt. 5.17% Fe2O3 and 20.40% Al2O3. These values are not compatible with TSE 11136 standard (max Fe2O3 %1, Al2O3 %14, TiO2 %0.30). Chemical properties of examined Esan bentonite (wt. 0.70% Fe2O3, 13% Al2O3, 0.05% TiO2) were suitable with TSE 11136 standard. Water absorption (%) is defined 10% in technical standard of wall tiles TSE EN 14411. Water absorption of ceramic bodies with Tokat-Reşadiye region bentonite is avarage 4.26% at 1140ᵒC. Water absorption of ceramic bodies with Esan bentonite is avarage 4.26% at 1140ᵒC and these values are under the values of TSE EN 14411 standard. Hardness of inspected ceramic bodies with Tokat-Reşadiye region bentonite were max. 3 (Mohs). Hardness of inspected ceramic bodies with Esan bentonite were max. 5 (Mohs) and these values were under the hardness values of literature. While increasing the firing temperature, hardness values increased for both inspected ceramic bodies.This condition is compateble with phase formation that determined by XRD analysis and downsizing and closing of the pores that determined by SEM. It has been determined that Tokat-Reşadiye region bentonite is not suitable for the ceramic industry applications according to the TSE 11136, TSE EN 14411 standard. In order to evaluate using Tokat-Reşadiye region bentonite in ceramic industry, components of the bentonite has to be developed in the various prosses considering the economic factors for the future.