Keywords: mesoporous, alumina, affinity, absorption, pH, retention
Summary:One important application for mesoporous alumina is as the adsorbent for retaining Molybdenum-99m in the Molybdenum/Technetium generators used for medical imaging throughout the world. In 2016, Fujimi created a novel mesoporous alumina material that could retain 6x, by weight, the amount of molybdenum than other commercially available mesoporous aluminas. Research has continued with several different mesoporous aluminas to study the affinity for different metal ions and how that affinity is affected by changes in pH. One commercially available mesoporous alumina, Brockmann, and two Fujimi prepared materials, MA2HS-B and MA C were used as the adsorbent materials. The following metal ions were studied: Calcium, Chromium, Cobalt, Copper, Lithium, Nickel, Magnesium, Molybdenum, Titanium, Zinc, and Zirconium. The pH range studied started as low as 1.5 and was increased to as high as 5.2 with dilute KOH. At pH values less than 2.5, the stability of each of the aluminas was compromised and as a result retention was generally low for all of the materials. At pH levels of around 2.5, many of the metals showed a moderate affinity for each of the aluminas, with the exception of titanium and zirconium, which showed complete absorption for each of the aluminas tested. At a pH of around 5.0, most metals showed an increased absorption for each alumina. The exceptions are lithium and magnesium which had a fairly low retention for every test condition. Fujimi’s MA C material was shown to be superior at pH levels greater than 2.0 than the other tested materials in this study. None of the tested aluminas are suitable for use in conditions requiring a pH of less than 2.0.