Pyrohydrolysis of CaCl2 waste for the recovery of HCl acid upon the synergistic effects from MgCl2 and silica

Song Zhou, Binbin Qian, Tahereh Hosseini, Anthony De Girolamo, Lian Zhang

Research output: Contribution to journalArticleResearchpeer-review

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 languageEnglish
Pages (from-to)3349-3355
Number of pages7
JournalACS Sustainable Chemistry and Engineering
Volume7
Issue number3
DOIs
Publication statusPublished - 4 Feb 2019

Keywords

  • Alkaline-earth-metal chlorides
  • Cl release
  • HCl regeneration
  • Pyrohydrolysis
  • Silica

Cite this

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title = "Pyrohydrolysis of CaCl2 waste for the recovery of HCl acid upon the synergistic effects from MgCl2 and silica",
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.",
keywords = "Alkaline-earth-metal chlorides, Cl release, HCl regeneration, Pyrohydrolysis, Silica",
author = "Song Zhou and Binbin Qian and Tahereh Hosseini and {De Girolamo}, Anthony and Lian Zhang",
year = "2019",
month = "2",
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language = "English",
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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 journalArticleResearchpeer-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

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JO - ACS Sustainable Chemistry & Engineering

JF - ACS Sustainable Chemistry & Engineering

SN - 2168-0485

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