Corrosion behaviour of vitrified heavy metals from industrial waste S.R.H. Mello-Castanho 1a , A.C. Silva 1a , W. Acchar 2b , A.M. Segadães 3c 1 Institute of Energy and Nuclear Research, IPEN-CCTM, 05508-000 São Paulo-SP, Brazil 2 Dept. of Physics, Federal University of Rio Grande do Norte (UFRN), 59072-970 Natal-RN, Brazil 3 Dept. of Ceramics and Glass Eng. (CICECO), University of Aveiro, 3810-193 Aveiro, Portugal a srmello@ipen.br, c acchar@dfte.ufrn.br, d segadaes@cv.ua. Keywords: galvanic waste, silicate glass, recycling, environment. Abstract. The vitrification process is an attractive route for the inertization treatment of hazardous industrial wastes. The corrosion resistance of this kind of materials is one of the most important requirements to ensure the long term retention of the toxic metals. In this work, silicate glasses with various waste concentrations were obtained using a galvanic sludge from metallurgical activities and glass forming rejects from ceramic activities. Glasses with several galvanic waste concentrations were obtained. The corrosion behaviour of the vitrified materials under various pH media was evaluated. The FTIR technique was used to investigate the glass structural modifications. Glasses containing 40 wt.% galvanic waste additions show higher resistance to corrosion media than those without waste additions. Introduction The adequate and safe management of hazardous industrial wastes involve complex aspects of many orders, such as sanitary, environmental, economic, industrial and cultural. In the specific case of the galvanic solid rejects, which contain transition and toxic heavy metals such as Nickel and Chromium, the legislation in most countries forbids their simple deposition on the ground. Vitrification has been proposed as an inertization alternative. The vitrification process used for industrial wastes is more complex than the simple dilution of the waste in a glass matrix. During melting, the waste may contribute with some metal oxides to the random glass network and the transition and heavy metal oxides, associated with the glass, may act as glass network formers or modifiers [1]. This behavior may be explained as follows: in a pure silica glass structure, each silica tetrahedron is linked with four other by the corner oxygen atoms (bridging oxygen, BO). Thus, all oxygen atoms are BOs and every Si atom is named Q 4 species. When modifier cations (R + and/or R ++ ) are added to the glass composition, some oxygen atoms will bond with the modifier cations, becoming non-bridging oxygens (NBOs), and some Si atoms are named Q n species. The presence of modifier cations in the glass network usually changes the glass characteristics, such as the melting point and the glass chemical durability. A characteristic behavior can occur with cations with coordination number higher than four, such as those generally present in the galvanic wastes. The Q n abundance is also affected by the presence of Boron or Aluminum, given that Al 3+ and B 3+ show a strong tendency to replace Si 4+ in the Q 4 species. The use of the vitrification process for toxic metals immobilization is based on the assumption that the chemical durability of the resultant glasses will reduce the contamination of the environment. Although one of the most important characteristics of a glass is its chemical durability, glasses cannot be considered rigorously inert. The glass chemical durability can be evaluated as corrosion resistance to water attack (hydrolytic resistance), acid attack and alkaline attack. The dissolution process is irreversible [2] and the presence of impurities and the complexity of the glass composition will have a strong influence in the dissolution behavior [3,4]. The aim of this work was to study the feasibility of using only industrial rejects of different origins to obtain glasses capable of immobilizing transition and heavy metals. Such capability was evaluated as chemical resistance to various corrosive media. Advances in Science and Technology Vol 45 (2006) pp 178-183 Online: 2006-10-10 © (2006) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AST.45.178 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.ttp.net. (ID: 193.137.168.16, Universidade de Aveiro, Aveiro, Portugal-16/04/15,16:21:29)