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Lookup NU author(s): Ning ZhangORCiD, Professor Lidija Siller
This is the of an article that has been published in its final definitive form by Elsevier BV, 2021.
For re-use rights please refer to the publisher's terms and conditions.
CO2 mineralisation is a process that can store the CO2 as a solid mineral permanently, to mitigate carbon emissions. Brines rich in alkaline earth metals present an attractive opportunity to trap CO2 in the form of insoluble carbonates. Moreover, this can be accomplished, as shown in this work, using flue gas concentrations of CO2 and at near-ambient temperatures, eliminating the need for energy-intensive CO2 capture step and heating of dilute aqueous solutions. The conventional alkaline substances to neutralise the solution, such as sodium hydroxide or amines, are costly, and the processes required to regenerate them (e.g. distillation or electrolysis) are energy intensive, which hinders the feasibility of this CO2 sequestration approach. We herein developed a process to remove chloride anions from alkaline brines by ion exchange, using lamellar structured materials, namely hydrotalcites (HT). These HT, which are layered double hydroxides prepared by co-precipitation method, release hydroxyl groups in exchange for chloride, sufficiently raising the pH of brines to enable the precipitation of carbonates during CO2 mineralisation. Several calcined-HT were synthesized using different ratios of magnesium and aluminium content, and various reaction temperatures and solid-to-liquid ratios were investigated for chloride removal. Moreover, the HT materials are recyclable for multiple usage by taking advantage of the HT’s ‘memory effect’ property. Gaseous CO2 and Na2CO3 solution were tested as the recharging agents, to replace the chloride anions from the spent HT interlayers and intercalate with HCO3- or CO32-, followed by a calcination process to produce the reusable calcined-HT. Several reaction cycles were conducted to evaluate the reusable property. It was found that the chloride removal efficiency remains over 70% after five cycles, and calcium utilisation efficiency of the brine carbonation process can surpass 90%. This unique cyclical closed-loop HT process thus presents a more cost- and energy-effective approach to brine carbonation than previous studies. In addition, the produced carbonates are of sufficient quality for a variety of applications that can further reduce the process cost of this type of CO2 sequestration.
Author(s): Zhang N, Santos RM, Siller L
Publication type: Article
Publication status: Published
Journal: Chemical Engineering Journal
Year: 2021
Volume: 404
Print publication date: 15/01/2021
Online publication date: 30/07/2020
Acceptance date: 25/07/2020
Date deposited: 15/10/2020
ISSN (print): 1385-8947
ISSN (electronic): 1873-3212
Publisher: Elsevier BV
URL: https://doi.org/10.1016/j.cej.2020.126450
DOI: 10.1016/j.cej.2020.126450
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