Calcination-free production of calcium hydroxide at sub-boiling temperatures

Sara Vallejo Castaño, Erika Callagon La Plante, Sho Shimoda, Bu Wang, Narayanan Neithalath, Gaurav Sant, Laurent Pilon

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Calcium hydroxide (Ca(OH)2), a commodity chemical, finds use in diverse industries ranging from food, to environmental remediation and construction. However, the current thermal process of Ca(OH)2 production via limestone calcination is energy- and CO2-intensive. Herein, we demonstrate a novel aqueous-phase calcination-free process to precipitate Ca(OH)2 from saturated solutions at sub-boiling temperatures in three steps. First, calcium was extracted from an archetypal alkaline industrial waste, a steel slag, to produce an alkaline leachate. Second, the leachate was concentrated using reverse osmosis (RO) processing. This elevated the Ca-abundance in the leachate to a level approaching Ca(OH)2 saturation at ambient temperature. Thereafter, Ca(OH)2 was precipitated from the concentrated leachate by forcing a temperature excursion in excess of 65 °C while exploiting the retrograde solubility of Ca(OH)2. This nature of temperature swing can be forced using low-grade waste heat (≤100 °C) as is often available at power generation, and industrial facilities, or using solar thermal heat. Based on a detailed accounting of the mass and energy balances, this new process offers at least ≈65% lower CO2 emissions than incumbent methods of Ca(OH)2, and potentially, cement production.

Original languageEnglish (US)
Pages (from-to)1762-1772
Number of pages11
JournalRSC Advances
Issue number3
StatePublished - Jan 6 2021

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)


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