Agnieszka Generowicz 1 Zygmunt Kowalski 2 Joanna Kulczycka 3 Agnieszka Makara 2 1 Institute of Water Supply and Environmental Protection, Cracow University of Technology, Warszawska, Cracow, Poland 2 Institute of Chemistry and Inorganic Technology, Cracow University of Technology, Warszawska, Cracow, Poland 3 Mineral and Energy Economy Research Institute, Polish Academy of Sciences, Wybickiego, Cracow, Poland Research Article Multi-Criteria Analysis for Optimization of Sodium Chromate Production from Chromic Waste The proposal of application of multi-criteria analysis and technological quality method for optimization of technological processes on the case study of sodium chromate production variants from waste was presented. The research on the use of chromic waste for the production of sodium chromate made it possible to determine the optimal process parameters. Technological quality method was used to define the value of criterions for multi-criteria analysis while multi-criteria analysis allowed determining the impact of criterions weights for ranking variants of technological process. Both methods in a complex way evaluate the degree of modernization of technologies, describing them qualitatively within the area of environmental, tech- nical, and the economic effects of the proposed technological variants. Based on the proposed evaluating criteria both methods yield comparable results. The most advan- tageous alternatives provided realization of the sodium chromate production process with the use of in-process recycling of chromic mud, off-site recycling of chromic tannery waste and on-site recycling of waste from the old chromic heaps. Keywords: Chromic waste; Multi-criteria analysis; Sodium chromate Received: June 14, 2010; revised: January 10, 2011; accepted: January 15, 2011 DOI: 10.1002/clen.201000203 1 Introduction Waste materials containing chromium are produced in many indus- trial branches. One-fifth of the total amount of the waste is produced in the chemical industry [1–7], mainly during the production of sodium chromate. Generally, there are approximately 5 million tons of toxic chromic wastes stored on heaps in Poland. The waste result- ing from the production of sodium chromate (the so-called post- chromic mud), containing up to 2% of chromium(VI) is particularly dangerous due to its carcinogenic effect. In many countries, there are special regulations and guidelines for chromium, i.e. The Occupational Safety and Health Administration in the US, which are designed to protect the public from potential adverse health effects [8]. In Poland, according to Polish regulation (waste catalogue) chromium waste from chromium compounds are not treated as dangerous substance [9]. The research on the use of chromic waste for the production of sodium chromate made it possible to deter- mine the optimal parameters for the production process of sodium chromate, which would in turn allow the choice of the optimal technological idea [2–6]. In order to evaluate the analyzed variants, a mathematical model describing the production process of sodium chromate (VI) was devised [10]. The model describes the process of obtaining sodium chromate (VI) in the function of selected process parameters and allows the determination of useful values for a practical process evaluation, such as mass proportions of applied raw materials, mass balances of basic technological nodes and tech- nological indicators, e.g. efficiency per unit, process efficiency, amount and content of chromium compounds in the chromic waste resulting from the process [10–12]. Up to the present time, the evaluation of the modification of the technological process of chromate (VI) production with the use of chromic waste has been conducted with various methods [11, 13–15], including the so-called method of technological quality Q T [15]. The basis for analyses with this method is a complex evaluation of the degree of technology modernization, which described qualitatively, compared technologies in the area of their impact on the environ- ment and economic effects of the implemented developed processes. The paper presents comparative environmental, technical, and economical assessment of the sodium chromate production variants with Q T method and multi-criteria analysis. Q T indices were used to determine the value of criterions for multi-criteria analysis on the example case study of sodium chromate production variants from Correspondence: Dr. J. Kulczycka, Mineral and Energy Economy Research Institute, Polish Academy of Sciences, Wybickiego 7, 31-261 Cracow, Poland E-mail: kulczycka@meeri.pl Abbreviations: A i , degree of validity; F, absolute value of analyzed indices; GWS, cumulated total hazard coefficient; k, toxic coefficient, K f , costs of particular process phases; M f , consumption of raw material in process phases; Q ED , environmental quality of technology; Q E , cumulated energy consumption; Q M , cumulated natural raw materials consumption; Q K , net production costs; Q L , work consumption; Q H , level of noise emission; Q T , technological quality; W C , criterion value; WS, cumulated hazard index; X f , energy used in particular process phases; ZS, cumulated hazard. 688 Clean – Soil, Air, Water 2011, 39 (7), 688–696 ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com