Quantification of potentially toxic compounds in anhydrous cements: optimization of leaching by thermal analysis for sustainable production of cements

The co-processing of waste in clinker synthesis is a widely adopted strategy to reduce the consumption of fossil fuels and natural raw materials. However, the incineration of waste may increase the release of potentially toxic compounds (PTCs) and volatile metals, raising concerns for the environment and human health. A major limitation in assessing these risks is the lack of suitable methods to directly quantify PTCs in anhydrous cement; existing approaches are typically limited to hydrated pastes. This study proposes a novel method for quantifying PTC in anhydrous cement by combining leaching tests and thermal analysis. The methodological framework involved: (i) identifying an acid solution capable of sustaining PTC quantification by prolonging reaction kinetics, (ii) selecting the leaching stage, and (iii) defining the optimal solid-liquid contact time. Portland cement samples were characterized, and the reactivity of different solutions was assessed by isothermal calorimetry prior to leaching tests. Results indicated that maintaining a pH between 0.65 and 0.70 optimizes the leaching solution, while the nitric acid/sodium hydroxide ratio must be adjusted explicitly for each cement type. Compared with the standard TCLP method, the proposed approach enabled the detection of 11 metals (Ba, Cr, Cu, Zn, Pb, Ni, La, V, Co, Sb, Mo, and Sn), demonstrating the effectiveness of the refined methodology.