Ibuted to newly formed carbonates (Figure 3c,d) [38,45,46]. In agreement with
Ibuted to newly formed carbonates (Figure 3c,d) [38,45,46]. In agreement with previous observations, rhombohedric calcite seems to cover the entire surface of your cenospheres upon carbonation (Figure 3d). This can be especially evident when comparing cenospheres in as-received (Figure 3a) and treated fly ashes (Figure 3c,d).Crystals 2021, 11,11,FOR PEER Evaluation Crystals 2021, x5 of five of 13Crystals 2021, 11, x FOR PEER REVIEW6 ofFigure FTIR-ATR analysis of untreated and carbonated fly ash samples. Figure 2.two. FTIR-ATRanalysis of untreated and carbonated fly ash samples.The morphologies with the starting and carbonated supplies were studied by SEM (Figure three). Essentially the most abundant elements of the HCFA are round to semi-spherical cenospheres, composed primarily of aluminosilicate glass and quartz [42,43]. The observed platy options are portlandite crystals, according to the morphology features [44] and the mineralogy observed with XRD (Figure 3b). Upon reaction with CO2 for the duration of the flue gas experiments, aggregates of rhombohedric crystals had been identified and attributed to newly formed carbonates (Figure 3c,d) [38,45,46]. In agreement with prior observations, rhombohedric calcite appears to cover the whole surface on the cenospheres upon carbonation (Figure 3d). That is especially evident when comparing cenospheres in asreceived (Figure 3a) and treated fly ashes (Figure 3c,d).(a) (b)(c)(d)Figure three. Representative SEM photographs of your (a,b) starting material, (c) concentrated 2 carbonated supplies at 7 bars Figure three. Representative SEM photographs of the (a,b) starting material,(c) concentrated COCO2 carbonated materials at 7 bars more than 4 h and (d) close-up of Figure 3c, showing PF-06873600 Epigenetics rhombohedral calcite crystals. more than 4 h and (d) close-up of Figure 3c, showing rhombohedral calcite crystals.More insights on the progress on the carbonation reaction might be gained from TPD evaluation. Figure four exhibits the derivative weight modifications as a function of temperature in the selection of 3050 . Untreated samples of fly ash are characterized by only one stage of mass loss, starting at 600 , that MCC950 NOD-like Receptor corresponds to precursor carbonates in the fly ash on account of all-natural carbonation. Inside the treated samples, 3 different mass loss stages can beCrystals 2021, 11,6 ofAdditional insights on the progress of your carbonation reaction might be gained from TPD evaluation. Figure four exhibits the derivative weight modifications as a function of temperature within the array of 3050 C. Untreated samples of fly ash are characterized by only one stage of mass loss, starting at 600 C, that corresponds to precursor carbonates inside the fly ash as a result of natural carbonation. Inside the treated samples, three different mass loss stages is often identified. The first a single, starting at 400 C, could be attributed to portlandite decomposition, which was made in the course of the hydration of original CaO [47]. The formation of portlandite could have an effect on the final carbonation efficiency, because the Ca in lime is fixed by hydration in portlandite and by carbonation in calcite. At larger temperatures, carbonate decomposition can take place in the variety from 600 to 650 C, leading to a much larger mass loss when compared with the untreated fly ash. The subsequent stage observed at T 650 C (illustrated by the optimistic slope with the TPD curve) indicates that further decomposition of extra thermally stable carbonates continues beyond the studied temperature variety, in agreement with Cwikof 14 Crystals 2021, 11, x FOR PEER Assessment 7 et al., 2018 [28.
