Indian Journal of Chemical Technology Vol. 16, January 2009, pp. 65-73 Thin layer chromatographic study of Indian bauxites P A Mohamed Najar 1 *, K R Janbandhu 1 , P G Bhukte 2 & R S Mishra 1 Analytical 1 and Bauxite Alumina 2 Divisions, Jawaharlal Nehru Aluminium Research Development and Design Centre Amaravati Road, Nagpur, 440 023, India Email: najarp@hotmail.com Received 12 November 2007; revised 7 November 2008 Thin layer chromatography (TLC) has been used for the detection and separation of Al 3+ , Fe 2+ , Si 4+ and Ti 4+ in bauxite. Thirty bauxite samples of different geological origin have been studied to identify the optimized chromatographic systems capable of selective separations of the constituents. Binary and ternary separations of Al 3+ , Fe 2+ , Ti 4+ and Si 4+ in bauxite were realized with chromatographic systems comprising various combinations of silica gel G, silica gel H and microcrystalline cellulose coated plates and aqueous mobile phases consisting alkali salt solutions, formic acid and hydrochloric acid etc. The chromatographic system consisting of silica gel H and mixture of 10% aqueous solutions of sodium chloride and formic acid in 8:2 (v/v) ratio was found to be the ideal combination for the analogous separation of Al 3+ , Fe 2+ and Ti 4+ in bauxites. The efficacy of optimized chromatographic system has been investigated by monitoring reproducibility of R F values and spot compactness with respect to change in bauxite geology, sample concentration and change of mobile phase composition. Chromatograms of the cations were quantitatively evaluated by scanning densitometry in comparison with wet analysis method. Keywords: Bauxite, TLC, Separation of Al 3+ , Fe 2+ , Si 4+ and Ti 4+ Bauxite is a general term applied to a variety of rock like materials containing hydrous aluminium oxide minerals mixed with impurities such as silica, iron, titanium, phosphorous, alkalies etc. with low organic components of natural origin. Though more than sixty chemical constituents in bauxite have been reported 1 , Al 2 O 3 , Fe 2 O 3 , SiO 2 , TiO 2 , and loss on ignition (LOI) generally constitute 99% of bauxite composition. The change in concentration ranges of major constituents in bauxite is decisive for its classification as well as utilization in metallurgical and non-metallurgical applications. The major metallurgical application of bauxite is in the production of aluminium and bauxite is considered as the most economical ore for the commercial production of hydrated aluminium oxide generally called alumina hydrate by Bayer chemical process that accounts 80-90% of bauxite consumption 2 . India is endowed with large reserves of bauxite containing various impurities, which to a great extent restrict their use in the refractory, abrasive and chemical industries etc. The major bauxite deposits of India are spread across the central Indian as well as east and west costal states and they are grouped into five major geological-geographical groups such as (i) Eastern Ghats, (ii) Central Indian, (iii) West Coastal (iv) Gujarat and (v) Jammu & Kashmir bauxites. The chemical, mineralogical and physico-mechanical properties of these groups widely vary depending upon the parent rock composition, mode of origin, geomorphological position and duration as well as the age of bauxite formation. The nature and concentration of naturally occurring mineralogical phases in bauxite is significant in the formulation of Bayer plant parameters like caustic concentration, digestion pressure, caustic consumption as well as the quantum of red mud (bauxite tailing) generation. The alumina R&D centers and plant laboratories generally employ conventional wet chemical analysis and instrumental analytical methods 3,4 like X-Ray fluorescence analysis (XRF) for the determination of oxide concentrations such as Al 2 O 3 , Fe 2 O 3 , SiO 2 , TiO 2 , and LOI in bauxite. Chromatography is a simple separation technique generally practiced in various analytical laboratories. The major chromatographic studies relevant to bauxite and related materials reported in the past engrossed the identification of organic acids in Bayer liquors by gas chromatography-mass spectrometry (GC-MS) 5 and ion chromatography (IC)