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 earlier observations, rhombohedric calcite appears to cover the whole surface in the cenospheres upon carbonation (Figure 3d). This can be specifically evident when comparing cenospheres in as-received (Figure 3a) and treated fly ashes (Figure 3c,d).Crystals 2021, 11,11,FOR PEER Charybdotoxin Technical Information Critique 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 2.2. FTIR-ATRanalysis of untreated and carbonated fly ash samples.The morphologies of the beginning and carbonated components were studied by SEM (Figure three). One of the most abundant elements of your 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 functions [44] plus the mineralogy observed with XRD (Figure 3b). Upon reaction with CO2 during the flue gas experiments, aggregates of rhombohedric crystals were identified and attributed to newly formed carbonates (Figure 3c,d) [38,45,46]. In agreement with preceding observations, rhombohedric calcite appears to cover the complete surface from the cenospheres upon carbonation (Figure 3d). This can be particularly evident when comparing cenospheres in asreceived (Figure 3a) and treated fly ashes (Figure 3c,d).(a) (b)(c)(d)Figure three. Representative SEM photographs with the (a,b) starting material, (c) concentrated two carbonated materials at 7 bars Figure three. Representative SEM pictures from the (a,b) starting material,(c) concentrated COCO2 carbonated materials at 7 bars more than four h and (d) close-up of Figure 3c, showing rhombohedral calcite crystals. over 4 h and (d) close-up of Figure 3c, displaying rhombohedral calcite crystals.Added insights on the progress from the carbonation reaction is usually gained from TPD analysis. Figure 4 exhibits the derivative weight adjustments as a function of temperature in the array of 3050 . Untreated samples of fly ash are characterized by only one particular stage of mass loss, beginning at 600 , that corresponds to precursor carbonates inside the fly ash as a consequence of all-natural carbonation. Inside the treated samples, 3 various mass loss stages can Etiocholanolone Cancer beCrystals 2021, 11,six ofAdditional insights around the progress of the carbonation reaction is usually gained from TPD evaluation. Figure four exhibits the derivative weight changes as a function of temperature inside the selection of 3050 C. Untreated samples of fly ash are characterized by only 1 stage of mass loss, beginning at 600 C, that corresponds to precursor carbonates inside the fly ash due to organic carbonation. Inside the treated samples, three various mass loss stages is usually identified. The initial a single, beginning at 400 C, may be attributed to portlandite decomposition, which was produced in the course of the hydration of original CaO [47]. The formation of portlandite could affect the final carbonation efficiency, because the Ca in lime is fixed by hydration in portlandite and by carbonation in calcite. At higher temperatures, carbonate decomposition can happen inside the range from 600 to 650 C, major to a a great deal larger mass loss when compared with the untreated fly ash. The subsequent stage observed at T 650 C (illustrated by the positive slope in the TPD curve) indicates that further decomposition of a lot more thermally stable carbonates continues beyond the studied temperature range, in agreement with Cwikof 14 Crystals 2021, 11, x FOR PEER Overview 7 et al., 2018 [28.
