Iron Removal using Magnesium Oxide

by John T. O'Connor, (M.ASCE), Prof. of Civ. Engrg.; Univ. of Illinois, Urbana, IL,
Barrett E. Benson, Grad. Student; Dept. of Civ. Engrg., Univ. of Illinois, Urbana, IL,

Serial Information: Journal of the Sanitary Engineering Division, 1970, Vol. 96, Issue 6, Pg. 1335-1348

Document Type: Journal Paper


The calcined magnesite-diatomaceous earth process is currently being used for the removal of iron from ground water supplies. However, information from controlled laboratory studies describing the mechanism of the reaction and the kinetics of iron removal has been lacking. The addition of finely divided MgO in dry form to waters of various pH reactions and alkalinities results in the gradual solution of MgO with approximately 3/4 dissolving in 10 min. Laboratory studies indicate that the rate of solution is not strongly influenced by the initial pH. Ferrous iron precipitation is incomplete within 10 min unless abundant oxygen is present, indicating that MgO accelerates the oxygenation of ferrous iron. Some adsorpiton of ferrous iron occurs on the MgO particle in the absence of oxygen. This appears to lower the rate of MgO solution. It is hypothesized that the gradual solution of MgO results in the formation of diffuse regions of high pH around the MgO particle surface where iron oxidation is greatly accelerated.

Subject Headings: Laboratory tests | pH | Iron (chemical) | Iron compounds | Magnesium | Particles | Groundwater | Kinetics

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