Abstract
In this paper, an efficient HCl acid recovery method from the mixture of alkaline-earth-metal chlorides waste was demonstrated via co-pyrohydrolysis in a laboratory-scale horizontal furnace in a temperature range of 700-1000 °C, and fixed additions of SiO 2 and steam. The synergistic effect of MgCl 2 on the HCl recovery from CaCl 2 was explored intensively. A double-sided effect was revealed. For the reaction temperatures below 1000 °C, the MgCl 2 addition delayed the HCl release through competing with CaCl 2 for the inclusion into silica matrix. In contrast, once the chloride mixtures were subjected to 1000 °C with a noticeable residence time (e.g., 2 h) and at a minimum molar ratio of 0.5 of MgCl 2 to CaCl 2 , the MgCl 2 addition promoted the HCl release remarkably, via promoting the conversion of Ca 3 (SiO 4 )Cl 2 into Ca 8 Mg(SiO 4 ) 4 Cl 2 . A portion of Mg 2+ derived from the early decomposition of MgCl 2 substituted the Ca(I) site in Ca 3 (SiO 4 )Cl 2 , thereby resulting in the formation of weak Mg-Cl bond that is in favor of the HCl release. Additionally, the remaining Mg 2+ consumed the excessive SiO 2 so as to cause the skeleton of [SiO 4 ] 4- to be fully affiliated and balanced by cations to form Ca 8 Mg(SiO 4 ) 4 Cl 2 in which the weaker ionic polarization between Ca 2+ and adjacent anions further enhanced the breakage of the Ca-Cl bonds.
| Original language | English |
|---|---|
| Pages (from-to) | 3349-3355 |
| Number of pages | 7 |
| Journal | ACS Sustainable Chemistry and Engineering |
| Volume | 7 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - 4 Feb 2019 |
Keywords
- Alkaline-earth-metal chlorides
- Cl release
- HCl regeneration
- Pyrohydrolysis
- Silica
Cite this
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Pyrohydrolysis of CaCl2 waste for the recovery of HCl acid upon the synergistic effects from MgCl2 and silica. / Zhou, Song; Qian, Binbin; Hosseini, Tahereh; De Girolamo, Anthony; Zhang, Lian.
In: ACS Sustainable Chemistry and Engineering, Vol. 7, No. 3, 04.02.2019, p. 3349-3355.Research output: Contribution to journal › Article › Research › peer-review
TY - JOUR
T1 - Pyrohydrolysis of CaCl2 waste for the recovery of HCl acid upon the synergistic effects from MgCl2 and silica
AU - Zhou, Song
AU - Qian, Binbin
AU - Hosseini, Tahereh
AU - De Girolamo, Anthony
AU - Zhang, Lian
PY - 2019/2/4
Y1 - 2019/2/4
N2 - In this paper, an efficient HCl acid recovery method from the mixture of alkaline-earth-metal chlorides waste was demonstrated via co-pyrohydrolysis in a laboratory-scale horizontal furnace in a temperature range of 700-1000 °C, and fixed additions of SiO 2 and steam. The synergistic effect of MgCl 2 on the HCl recovery from CaCl 2 was explored intensively. A double-sided effect was revealed. For the reaction temperatures below 1000 °C, the MgCl 2 addition delayed the HCl release through competing with CaCl 2 for the inclusion into silica matrix. In contrast, once the chloride mixtures were subjected to 1000 °C with a noticeable residence time (e.g., 2 h) and at a minimum molar ratio of 0.5 of MgCl 2 to CaCl 2 , the MgCl 2 addition promoted the HCl release remarkably, via promoting the conversion of Ca 3 (SiO 4 )Cl 2 into Ca 8 Mg(SiO 4 ) 4 Cl 2 . A portion of Mg 2+ derived from the early decomposition of MgCl 2 substituted the Ca(I) site in Ca 3 (SiO 4 )Cl 2 , thereby resulting in the formation of weak Mg-Cl bond that is in favor of the HCl release. Additionally, the remaining Mg 2+ consumed the excessive SiO 2 so as to cause the skeleton of [SiO 4 ] 4- to be fully affiliated and balanced by cations to form Ca 8 Mg(SiO 4 ) 4 Cl 2 in which the weaker ionic polarization between Ca 2+ and adjacent anions further enhanced the breakage of the Ca-Cl bonds.
AB - In this paper, an efficient HCl acid recovery method from the mixture of alkaline-earth-metal chlorides waste was demonstrated via co-pyrohydrolysis in a laboratory-scale horizontal furnace in a temperature range of 700-1000 °C, and fixed additions of SiO 2 and steam. The synergistic effect of MgCl 2 on the HCl recovery from CaCl 2 was explored intensively. A double-sided effect was revealed. For the reaction temperatures below 1000 °C, the MgCl 2 addition delayed the HCl release through competing with CaCl 2 for the inclusion into silica matrix. In contrast, once the chloride mixtures were subjected to 1000 °C with a noticeable residence time (e.g., 2 h) and at a minimum molar ratio of 0.5 of MgCl 2 to CaCl 2 , the MgCl 2 addition promoted the HCl release remarkably, via promoting the conversion of Ca 3 (SiO 4 )Cl 2 into Ca 8 Mg(SiO 4 ) 4 Cl 2 . A portion of Mg 2+ derived from the early decomposition of MgCl 2 substituted the Ca(I) site in Ca 3 (SiO 4 )Cl 2 , thereby resulting in the formation of weak Mg-Cl bond that is in favor of the HCl release. Additionally, the remaining Mg 2+ consumed the excessive SiO 2 so as to cause the skeleton of [SiO 4 ] 4- to be fully affiliated and balanced by cations to form Ca 8 Mg(SiO 4 ) 4 Cl 2 in which the weaker ionic polarization between Ca 2+ and adjacent anions further enhanced the breakage of the Ca-Cl bonds.
KW - Alkaline-earth-metal chlorides
KW - Cl release
KW - HCl regeneration
KW - Pyrohydrolysis
KW - Silica
UR - http://www.scopus.com/inward/record.url?scp=85061081792&partnerID=8YFLogxK
U2 - 10.1021/acssuschemeng.8b05513
DO - 10.1021/acssuschemeng.8b05513
M3 - Article
VL - 7
SP - 3349
EP - 3355
JO - ACS Sustainable Chemistry & Engineering
JF - ACS Sustainable Chemistry & Engineering
SN - 2168-0485
IS - 3
ER -