Magnesium oxide was historically known as magnesia alba (literally, the white mineral from Magnesia â€“ other sources give magnesia alba as MgCO3), to differentiate it from magnesia negra, a black mineral containing what is now known as manganese
Calcining at different temperatures produces magnesium oxide of different reactivity. High temperatures 1500 â€“ 2000 Â°C diminish the available surface area and produces dead-burned (often called dead burnt) magnesia, an unreactive form used as a refractory. Calcining temperatures 1000 â€“ 1500 Â°C produce hard-burned magnesia, which has limited reactivity and calcining at lower temperature, (700â€“1000 Â°C) produces light-burned magnesia, a reactive form, also known as caustic calcined magnesia. Although some decomposition of the carbonate to oxide occurs at temperatures below 700 Â°C, the resulting materials appears to reabsorb carbon dioxide from the air.
Magnesium oxide is used extensively in the soil and groundwater remediation, wastewater treatment, drinking water treatment, air emissions treatment, and waste treatment industries for its acid buffering capacity and related effectiveness in stabilizing dissolved heavy metal species.
Many heavy metals species, such as lead and cadmium are most soluble in water at acidic pH (below 6) as well as high pH (above 11). Solubility of metals affects bioavailability of the species and mobility soil and groundwater systems. Most metal species are toxic to humans at certain concentrations, therefore it is imperative to minimize metal bioavailability and mobility.