Characterization of Portland cement pastes with silica addition aiming at Cr(VI) immobilization

Abstract

In the scope of sustainability, the generation of different residues through human activities requires the exploration of techniques for final disposal. Among these residues, there are agricultural residues, as well as the residues of heavy metals, both potentially polluting. This work reports the analysis on the immobilization of chromium (VI) in Portland cement pastes (PC) with the addition of silica (SiO₂) obtained from rice husk ash (RHA). The cement pastes were evaluated from the perspective of mechanical properties through the compression test. Regarding the hydration development, the pastes were evaluated by SEM, XRD and FTIS. Aiming at the study of Cr(VI) immobilization, solubilized extracts were obtained for analysis through UV-VIS spectrophotometry. The results suggest that the SiO₂ from the RHA showed a predominantly amorphous. Regarding the pastes, the comparison of the strength of the different traits at the same ages revealed that they are not significantly different. As to the XRD, the results suggest that, in the traits with K₂Cr₂O₇, there are alterations in the hydration process. The immobilization efficiency resulted greater than 99%, but there was no favorable effect of the addition of silica to PC in the immobilization of chromium (VI).