The role of temperature on Cr(VI) formation and reduction during heating of chromium-containing sludge in the presence of CaO

Chromium-ruthenium oxide solid solution electrocatalyst for highly efficient oxygen evolution reaction in acidic media

“…6b). The primary peaks at ~576.0 eV correspond to Cr (IV) 2 p 3/2 46,47 . For Cr (IV) 2 p 3/2 of Cr 0.6 Ru 0.4 O 2 (550), a shift to lower binding energy is observed compared to CrO 2 , implying a higher electron density at Cr sites, which confirms the withdrawing effect of Cr (IV) in Cr 0.6 Ru 0.4 O 2 (550).…”

Influence of Cr3+, Co2+ and Cu2+ on the formation of calcium silicates hydrates under hydrothermal conditions at 200 °C

“…The previous results were confirmed by a Simultaneous Thermal Analysis: a broad endothermic effect at 84°C temperature can be assigned to the removal of chemically bound water in semicrystalline or amorphous CSH [45][46][47] (Figure 3). Since the results of XRD do not showed the formation of crystalline compounds in CaO-SiO 2 -Al 2 O 3 -Cr(NO 3 ) 3 -H 2 O system (except calcium carbonate), the effect at 272°C temperature can be attributed to the decomposition of low crystallinity compounds (CAH, CASH or compounds containing nitrate anion) [46,48] as well as to Cr 3+ oxidation to Cr 6+ (chromates formation) [49]. Meanwhile, the endothermic effects in a 550-700°C temperature range can be assigned to the formation of chromates [49] and decomposition of calcium carbonate.…”

“…Since the results of XRD do not showed the formation of crystalline compounds in CaO-SiO 2 -Al 2 O 3 -Cr(NO 3 ) 3 -H 2 O system (except calcium carbonate), the effect at 272°C temperature can be attributed to the decomposition of low crystallinity compounds (CAH, CASH or compounds containing nitrate anion) [46,48] as well as to Cr 3+ oxidation to Cr 6+ (chromates formation) [49]. Meanwhile, the endothermic effects in a 550-700°C temperature range can be assigned to the formation of chromates [49] and decomposition of calcium carbonate. Furthermore, exothermic effect with a shoulder reflecting recrystallization process of C-S-H (I) (864°C) and C-S-H (II) (880°C) to wollastonite were observed above 800°C (Figure 4).…”

Effect of Temperature on Hexavalent Chromium Formation in (Al,Cr)₂O₃ with Calcium Aluminate Cement in Air

“…[7][8][9][10][11][12][13] Cr(VI) is known to be highly soluble in water and toxic and thus easily enter into ground water and food chain, [14][15][16][17][18] which poses a serious threat to the human and environment. [19][20][21][22][23] Therefore, how to safely use Cr-containing refractories has become an issue of great concern.…”