Avaliação de compostos potencialmente tóxicos em cimento anidro: proposta de método quantitativo por ensaios de lixiviação

Abstract

Safe, effective, and economically viable solutions are essential given the importance of reducing the environmental impact of cement production. The use of waste co-processing as an energy source as well as a raw material in the synthesis of Portland cement clinker has been used to reduce the demand for fossil fuels and natural raw materials in cement production. However, the incineration of these materials can result in increased levels of potentially toxic compounds (PTCs) in the kiln system, including highly volatile heavy metals such as lead, cadmium and others, which are of great environmental concern and can pose risks to human health. One of the gaps in the study of these CPTs is their quantification in anhydrous cement. The aim of this research is to propose a method for quantifying potentially toxic compounds in anhydrous cement by means of leaching tests. To this end, analytical techniques were applied to characterize samples of commercial Portland cement and cements produced in the laboratory, such as granulometry, Blaine test, XRF and XRD. Calorimetry tests were then carried out with different solutions to assess the stages of cement hydration during the leaching test. After defining the solution, the leaching tests were carried out. Finally, based on the results of the tests carried out, a specific method for quantifying CPTs for anhydrous cements was proposed. The results obtained through calorimetric analysis indicated that, although the same leaching solution was used for all the cements tested, variations were observed in the induction times and setting times associated with each type of cement. In relation to the use of the solution defined in the leaching test, the proposed method was able to analyse 11 metals. By contrasting the quantification results obtained according to the guidelines of NBR 10005 and TCLP 1311 with the results generated by the method used in this study, an improved quantitative precision was found after the methodological procedure was refined.