Application of Micro-X-ray Fluorescence Analysis for the Characterization of Industrial Wastes Maria D. Alba,* ,† Patricia Aparicio, ‡ Jose M. Benı ´tez, § Miguel A. Castro, † Maria Dı ´az, § and M. Mar Orta † Instituto Ciencia de los Materiales de SeVilla, CSIC-UniVersidad de SeVilla, AVenida Americo Vespucio, 49, 41092 SeVilla, Spain, Departamento Crystalografı ´a Mineralogı ´a y Quı ´mica Agrı ´cola, UniVersidad de SeVilla, AVenida Reina Mercedes s/n, 41012 SeVilla, Spain, and BEFESA Centro de I+D+i, Fuente del Rey, Prolongacio ´n c/ Don Remondo s/n, 41007 Dos Hermanas, SeVilla, Spain The issue of how to improve product quality and product yield in a short period of time is becoming more critical in many industries. Thus, shorter delay times between laboratory analysis and process correction are important in process control. Elimination of sample handling and operator manipulation is desirable. The present article proposes micro-X-ray fluorescence (µXRF) as an economical control method for industrial product quality with a minimum time cost. Samples from different industrial processes have been chosen and analyzed by XRF and µXRF. The results show that the two techniques give similar results and that µXRF allows the waste to be classified and is able to detect problems in the production process. 1. Introduction Quality control in waste materials involves many factors, such as the instruments to be applied to chemical processes to improve yield, increase throughput, or maintain quality. 1,2 Moreover, the issue of how to improve product quality and product yield in a brief period of time becomes more critical in many industries. Even though industrial processes include a very wide range of reactions of different natures, there are two common and general key problems to solve: how to optimize operating conditions and how to perform online monitoring and control of the system. 3 Because process production rates are required to be optimized at a maximum, the delay between laboratory analysis and process correction of the production line becomes more significant and leads to cost increases in many commercial applications. Elimination of sample handling and operator manipulation is desirable. Although many spectroscopic techniques that measure el- emental composition have been employed for industrial analysis, including optical emission [flame, arc/spark, inductively coupled plasma (ICP), glow discharge, and laser ablation], atomic absorption (AA), and X-ray fluorescence (XRF), the latter continues to be one of the most widely used techniques for solids analysis. 4 Within the XRF field, the demand from industry and researchers for cost-effective, rapid, and nondestructive quantita- tive analysis has led to the development of a wide range of commercial XRF spectrometers with different configurations available to satisfy each requirement. 5 In particular, micro-X- ray fluorescence (µXRF) is a simple and fast technique for direct elemental analysis and provides a powerful tool to solve a variety of materials-based problems. The principal advantages of µXRF are that it provides nondestructive analysis and requires little or no sample preparation, so that it is less time-consuming than other methods, such as AA-ICP. 6 Among µXRF analytical applications, several studies have risen to the challenge presented by European Union directives in terms of the recycling of waste and landfill issues. 7 The present article proposes µXRF as a tool that can provide an economical control method, after an initial financial investment, of industrial product quality with a minimum cost. A collaborative project between the University of Seville, Seville, Spain, and BEFESA, an international company special- izing in the integral management of industrial wastes, is focused on assessing and rendering inert several industrial wastes through their incorporation into the synthesis processes of ceramic materials such as bricks and concrete. 8 To select those industrial wastes with promising properties as candidates to be used in ceramic materials synthesis, a systematic study of the compo- sitional variation of wastes was performed during one year, with conventional wavelength-dispersive X-ray fluorescence (WDXRF) and µXRF being used as experimental techniques. The promis- ing results obtained by µXRF have led us to evaluate the general use of this technique as a fast and economical method for industrial production control. Thus, this article describes the potential industrial application of micro-X-ray fluorescence for materials analysis for various industrial processes and quality control. In particular, the application of µXRF to the control of the chemical composition of industrial wastes is analyzed. For this purpose, we have chosen a set of wastes from different industrial processes and have compared the results obtained from both XRF methods. This article describes not only the advantages of using a fast and in situ procedure to determine industrial waste compositions, but also the practical consequences of using that methodology, such as the classification of different kinds of wastes coming from a unique industrial process (e.g., dusts related to steelmak- ing) and the identification of particular changes in the waste compositions that can be used to optimize the operating conditions of their industrial processes, for example, waste from zinc recovery. First, we try to establish a general methodology for determining the waste composition by XRF microanalysis by comparing these results with the known composition determined by WDXRF, and second, we apply the proposed methodology to two unknown waste samples. * To whom correspondence should be addressed. Tel.: +34 954489546. Fax: +34 954460665. E-mail: alba@icmse.csic.es. † Instituto Ciencia de los Materiales de Sevilla, CSIC-Universidad de Sevilla. ‡ Departamento Crystalografı ´a Mineralogı ´a y Quı ´mica Agrı ´cola, Universidad de Sevilla. § BEFESA Centro de I+D+i. Ind. Eng. Chem. Res. 2010, 49, 2348–2352 2348 10.1021/ie901716w  2010 American Chemical Society Published on Web 01/21/2010