Physicochemical Properties of Reactive Mgo at Different Alkali Precursors and Calcination Temperatures

Abstract

Commercial production of magnesium oxide (MgO) traditionally involves the decomposition of carbonate phases and releasing significant amounts of carbon dioxide (CO2). Another sustainable alternative is extracting MgO from highly concentrated reject brine waste from desalination plants. Thus, this study investigates the influence of alkali sources (sodium hydroxide (NaOH) and ammonium hydroxide (NH4OH)) and calcination temperatures (550°C and 650°C) at a fixed alkali/Mg2+ ratio of 2 on the overall properties of MgO. Results reveal that MgO_NaOH exhibits less density, higher specific surface area (SSA), and better reactivity compared to MgO_NH4OH, attributed to its smaller crystallite size and reduced agglomeration. Lower calcination temperature (550°C) consistently produced better-quality MgO than 650°C. XRD and TGA analyses show that the MgO_NaOH sample requires higher temperatures for complete conversion to MgO due to the stabilizing effect of Na+ ions, which slow down brucite’s decomposition. These findings provide valuable insights into optimizing MgO production from reject brine, presenting a more efficient pathway for sustainable resource utilization.

Keywords: Magnesium oxide, Reject brine, Desalination, NaOH, NH4OH