Production of reactive magnesia from desalination reject brine and its use as a binder

• Published in: Journal of CO2 utilization 2021-02, Vol.44, p.101383, Article 101383
• Main Authors: Ruan, Shaoqin, Yang, En-Hua, Unluer, Cise
• Format: Article
• Language: English
• Subjects: Carbon footprint; Mechanical performance; Production; Reject brine; Synthetic magnesia
• ISSN: 2212-9820; 2212-9839
• DOI: 10.1016/j.jcou.2020.101383

•Feasibility of producing and using MgO cement from desalination reject brine was studied.•Samples with synthetic MgO revealed higher strengths than those with commercial MgO.•Higher dissolution and reactivity of synthetic MgO led to enhanced hydration and carbonation.•Production of the alkali base had a major environmental impact in MgO production.•MgO obtained from reject brine can save natural resource and sequester CO2 in concrete. This study investigated the feasibility of producing reactive MgO cement from reject brine obtained from a desalination plant and evaluated its use as a binder in comparison to a commercial MgO. The mechanical performance of the samples cured under carbonation conditions for up to 28 days were further supported by x-ray diffraction (XRD), thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) and field emission scanning electron microscopy (FESEM) analyses. Samples involving synthetic MgO revealed higher strengths than those with commercial MgO, in line with the higher reactivity of the former. The increased dissolution of synthetic MgO led to its enhanced hydration and carbonation, resulting in samples with denser structures and improved performances. The findings highlighted issues regarding the large-scale production of MgO from reject brine and CO2 emissions of this process. The major environmental impact was associated with the production of the alkali base (NaOH), which could be improved via the identification of sustainable alkali sources used during production. Overall, the production of MgO from reject brine can save natural resources and pave the way for the sequestration of CO2 as stable carbonates in cement-based mixes.