Synthesis and characterization of some mixed metal hydroxides and their applications

Abstract

Chapter 1: The present work has been designed and carried out by keeping in mind the proliferation of interest over the chemistry of quotMixed Metal Layered Hydroxidesquot (MMLH) in recent times. These materials are used in various fields e.g. (A) Medical and related application; (B) Adsorbents; (C) Toxic gas remover; (D) Catalysts and catalyst precursors; (E) Anion exchangers; (F) Clay viscosity modifier etc. Introduction chapter provides a thorough background with an extensive literature survey of these materials. In the context of the present work, various aspects like synthesis of MMLH through different techniques, crystallographic characterisation of synthesised products, solid-liquid, solid-gas adsorption for combating pollution and rheology of clay-water systems containing MMLH were studied. Chapter 2: In the synthesis part, mainly two types of syntheses of MMLH were concentrated - the alkaline pH precipitation and the acidic pH oxide hydrolysis methods. In the alkaline pH synthesis, the effects of shaking and non-shaking conditions on crystallinity were studied. Additionally, the effect of starting pH on bi : tri-valent metal ion ratio in the product was studied by carrying out the precipitation by lowering the pH to 10 from high pH (=13) aluminate solutions and also by increasing the pH to 10 from low pH (=4) salt solutions. For successful synthesis of MMLH in acidic pH through hydrolysis of metal oxides, the oxide must have an extremely low solubility in water. Chapter 3: Crystallographic unit cell parameter for unreported Cu-Cr-Cl MMLH phase synthesised by oxide hydrolysis have been calculated from XRD data by computer aided interpretational softwares. A set of ordered unit cell parameters was assigned with a= 5.3902 A and c= 46.5149 A of a hexagonal crystal system. The ordered arrangement of Cu2+ and Cr3+ ions in the lattice is ascribed to (a) change of volume of cu2+ octahedra due to their d9 Jahn-Teller distorted structure and (b) higher Trivalent/ (Trivalent+Bivalent) ratio in Cu-Cr MMLH. Like Cu-Cr-Cl...