A Novel Method for Preparation of In₂O₃, Bi₂O₃ and Sb₂O₃ Oxides Using Urea at Elevated Temperature

Abstract

The In2O3, Bi2O3 and Sb2O3 oxides were synthesized by a novel reaction of urea with InCl3, BiCl3 and SbCl3 respectively, in an aqueous media at ~ 90 oC. The infrared spectra and microanalysis, CHN, of the solid products resulted indicate that the absence of the bands of urea, but appearing the characteristic bands of oxides. A general mechanism describing the formation of oxides and decomposition of urea are suggested.

Keywords

In₂O₃, Bi₂O₃, Sb₂O₃ and urea

Introduction

Urea and their derivatives are known to be the parent compound of a large and interesting class in both organic and inorganic compounds; it is used as a starting material for the synthesis of many applied compounds. The literature revels that urea is forming coordinate bonds with many metal ions at room temperature in aqueous and non aqueous media through its oxygen or nitrogen atoms depending on the type of metal ion used [1-8]. From the chemical viewpoint, the reaction of metal salts with urea at high temperature has recently gained increasing interest [7-14]. The nature of the reaction products depend strongly on the type of metal ions and so the metal salt used. In our previously studies referenced by us [7-14] concerning the reaction of urea with metals such as Co( III), pb(II), Sn(II), Cr(III), Fe(III), Au(III), Sn(IV), V(V) and Mo(IV) at high temperature demonstrate that the types of metal ions beside their anions have a pronounced effect on the nature of the reaction products. The published papers owned by us in this trend of the reaction of urea with different metal salts at elevated temperature lead to discovering a novel method for preparation pbCO₃ and CoCO₃ [10], lanthanide carbonates [12], limonite, FeO(OH) [9], 2ZnCO₃.3Zn(OH)₂ [8], and SnOCl₂.2H₂O [7].

The aim of this publication is to report the synthesis and characterization study of the In₂O₃, Bi₂O₃ and Sb₂O₃ oxides resulted from a novel oxidation reduction reaction between urea with InCl₃, BiCl₃ and SbCl₃, respectively, in an aqueous solution at ~ 90 °C.

Experimental

All chemicals used throughout this study were Analar or extra pure grade. The white oxides, In₂O₃, Bi₂O₃ and Sb₂O₃ were prepared by mixing equal volumes of aqueous solutions of 0.1M of InCl₃, BiCl₃ and SbCl₃ and 1.0 M of urea. The mixtures were heated on a water bath to approximately 90°C for about ~24 h. The white colored precipitate filtered off, washed several times with bi-distilled water and dried in vacuo over CaCl₂. The elemental analysis for the obtained products shows the absence of carbon, hydrogen and nitrogen elements. The percentages of indium, bismuth, and antimony were determined by using thermogravimetric method. The infrared spectra of the reactants and the solid products obtained were recorded from KBr discs using a Bruker FT-IR Spectrophotometer.

Results and Discussion

The reaction of aqueous solutions of urea with InCl₃, BiCl₃ and SbCl₃, produces clear white colored oxides, In₂O₃, Bi₂O₃ and Sb₂O₃. The formation of these oxides upon the heating of an aqueous mixture of InCl₃, BiCl₃ and SbCl₃, respectively, with urea may be understood as follows:

For the reaction mechanisms an oxidation process for In(III), Bi(III) and Sb(III) occurs during the decomposition of urea into ammonia, carbon dioxide and hydrogen chloride gases. The infrared spectra of synthetic oxides products are shown in Fig. 1. The infrared spectra of the obtained products show no bands due to characteristic groups of urea (carbonyl and amide groups), but the bands associated to the oxides are observed [15]. Based on this observation, along with that obtained from elemental analysis data as well as determination of metals In(III), Bi(III) and Sb(III), the fact that infrared spectra of commercially obtained In(III), Bi(III) and Sb(III) are the same as that of the reaction products.

Figure 1: Infrared spectra of the product resulted from the reaction of urea with InCl₃, BiCl₃ and SbCl₃.

Figure 1a: Infrared spectrum of In₂O₃ oxide

Figure 1b: Infrared spectrum of Bi₂O₃ oxide

Figure 1c: Infrared spectrum of Sb₂O₃ oxide

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