Distribution of Additives in Single-Modified TiO 2
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Distribution of Additives in Single-Modified TiO2 Marta A. Gleń1 and Barbara U. Grzmil1 1 West Pomeranian University of Technology, Szczecin, Institute of Chemical and Environment engineering, 70-322 Szczecin, Pułaskiego 10, E-mail: [email protected] ABSTRACT In the present work the influence of different modifiers, calculated to B2O3, CeO2, Sb2O3, ZnO, and ZrO2, on their distribution in TiO2 is investigated. The phase composition and phase transformation of prepared rutile-TiO2 is determined by the selective leaching method, ICP-AES, XRD and FT-IR techniques. The addition of Sb2O3 to TiO2 has no influence on the anatase–rutile phase transformation, CeO2 and ZrO2 act as inhibitors of the TiO2 phase transformation and the addition of ZnO or B2O3 to TiO2 accelerates rutile formation. It is observed that boron is located in TiO2 in the form of soluble B2O3, zinc partly reacts with titanium forming co-phase TiZn2O4 and antimony addition to TiO2 presumably causing the formation of a co-phase of Sb with Ti. Cerium forms a separate phase, CeO2, and reacts partly with titanium, probably creating cophase, CexTi(1-x)O2 (for example Ce0.8Ti0.2O2). Zirconium addition in TiO2 forms separate ZrO2 phase and solid solution of Zr with Ti. INTRODUCTION Titanium dioxide crystallizes in three naturally occurring polymorphous modifications: anatase, brookite and rutile. Anatase is a superior photocatalytic material for air and water purification, water disinfection and hazardous waste remediation [1]. Rutile plays the most important role in almost all inorganic pigments. Rutile pigment is mainly used in paint and coating industries, but additionally it is widely applied in paper, artificial fibre, plastic and rubber sectors of the market [2]. The polymorphous anatase-rutile phase transformation is affected by the kind and contents of additives present in calcined titanium dioxide. Their distribution both on the surface and in the bulk of titanium dioxide can act as promoters or inhibitors of the transformation, presence of rutile nuclei, particle size, temperature and calcination time [3-7]. EXPERIMENT The starting material is technical grade hydrated titanium dioxide (HTD) as a concentrated suspension containing 40 wt % of TiO2. It is an indirect product from the industrial production of TiO2 with the sulfate method. The modifier solutions are prepared by dissolving Sb2O3 in HCl aqueous solution and H3BO3, Ce(NO3)3, ZnSO4, Zr(SO4)2 in distilled water. Solutions of modifying agents (calculated to B2O3, CeO2, Sb2O3, ZnO, ZrO2) are introduced to HTD. Contents of B2O3, CeO2, Sb2O3, ZnO, or ZrO2 in TiO2 are changed respectively: 0.06-0.34 mol%, 0.02-0.14 mol%, 0.01-0.08 mol%, 0.05-0.3 mol%, and 0.03-0.19 mol%. The obtained pulp after thorough mixing is transferred to an evaporating dish and inserted into a laboratory muffle furnace heated to the desired temperature. The prepared samples, for investigations of the anatase-rutile phase transformation and modifiers’ distribution, are calcined for 1 h at 700, 750, and 800 ºC for TiO2 modified wi
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