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Abstract--Hydroxy-chromium solutions were prepared from chromium nitrate solutions by adding NaOH with OH/Cr = 2.The solutions were treated at 20~ and 60~ The hydrolysis "times were from 1 to 100 days. Polymeric species in hydrolyzed chromium solutions were followed by visible absorption spectra within the range 325-800 nm and by pH measurement. OH-Cr-smectite with high d(001) spacing (2.07 nm) was obtained when hydroxy-chromium solution was prepared at 60~ and with 1-day hydrolysis. When this sample was heated up to 350~ the basal spacing collapsed at 1.8 nm.The samples were characterized by X-ray diffraction and N2 adsorption-desorption isotherms.

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The aim of the manuscript was to analyze the structural and textural changes of the titanium in host matrix clay at room temperature and after thermal treatment. Materials and MethodsA montmorillonite supplied by Georgia Kaolin Co. was used in this study and referred to as E. The E sample is a clay mineral with high montmorillonite as clay composition. Quartz and α-cristobalite impurities in low proportions were detected in the sample. The montmorillonite has a cation-exchange capacity (CEC) of 110 meq/100g and the following structural formula: (Na 0.32 Titanium-solutionsThe titanium-solutions (containing partially hydrolyzed titanium cations) were obtained by different methods: a) using a TiCl 4 solution and 6.0 M HCl 5 , where the final Ti concentration was 0.80 M, and the HCl/Ti ratio was 1.22. The solution was aged for 3 hours at 20 °C before use (TiT-solution); b) a TiCl 4 solution was slowly added to absolute alcohol (ethanol), this solution was then added to glycerol (50% v.v -1 in water) following Lin et al. 18 and Bovey et al. 8 . This was named as TiG solution. Preparation of titanium-claysNatural montmorillonite clay (E) and acid treated montmorillonite clay (AE) were used as clays to prepare OH-Ti-clay. The acid activated montmorillonite (AE) was prepared by treating the montmorillonite with a 6 NH 2 SO 4 solution at boiling temperature for 30 minutes with a solid/acid ratio of 5%w.v -1 . The OH-Ti-clays were obtained by adding OH-Ti-solution addition drop wise to a stirred suspension of montmorillonite clay in water. After 4 hours in continuous stirring, the solid was separated by centrifugation, and washed several times with distilled water until being chloride free. The amount of Ti added to the solid was *e-mail: volzcris@netverk.com.ar Thermal Behaviour of Titanium in Host Matrix ClayCristina Volzone*, Ana María Cesio Titanium in hosted by a clay matrix has important applications in a variety of catalysts. However, there is insufficient information about of textural and structural characteristics of the titanium in matrix clay at room temperature and after thermal treatment. In this study, titanium in host matrix clay was obtained by treating montmorillonite clay minerals with different OH-Ti solutions. The titanium-solutions containing partially hydrolyzed titanium were obtained using a TiCl 4 solution with and without the addition of glycerol. The amount of Ti added to the solid was 20 mmol Ti per gram of clay. Thermal treatments were carried out at 500 and 1,000 °C in an air atmosphere. The solids were characterized by X ray diffraction, thermal analyses, infrared spectroscopy, N 2 adsorption-desorption isotherms. The products presented different structural and textural characteristics and, after calcination at 1,000 °C, anatase and rutile in different proportions were present in the samples. Centro de Tecnología de Recursos Minerales y Cerámica (CETMIC)-CIC/ CONICET, La

Beidellite clay mineral after intercalation of OH-Cr(III) species were thermally analyzed up to 1350 °C in oxygen and nitrogen atmospheres. OH-Cr-beidellite can be used as a pillared clay precursor for catalysis or as adsorbent applications. However, in this paper beidellite enriched in chromium were analyzed at different thermal treatments up to high temperature for evaluating structural changes for possible future ceramic applications. The structural changes were followed by thermal analysis and X-ray diffraction. The thermal treatment of OH-Cr-beidellite in oxygen and nitrogen atmospheres developed different mineralogical phases up to 1050 °C, but at higher temperatures, the same phases were developed in both atmosphere treatments. Eskolaite phase (Cr2O3) appeared in the sample after heating at 400 °C in oxygen atmosphere, whereas grimaldite (CrO-OH) in nitrogen atmosphere, maintaining the starting phases. At 1000 °C the raw clay minerals disappeared, as it is knew. At 1050 °C in nitrogen atmosphere, grimaldite was absent and eskolaite appeared. At 1350 °C in the samples calcined in both atmospheres, quartz, cristobalite and mullite as the main phases and in lower contents aluminum oxide and aluminum-chromium oxide [(Al,Cr)2O3] were present.