Abstract Synthesis of a novel alumina ⁹⁹Mo-molybdate(VI) gel matrix of high Mo(VI) content and reproducible separation indices of the generated ^99mTc radionuclde are described and briefly discussed. Similar mixture solutes of aluminate and low specific activity ⁹⁹Mo-molybdate(VI) anions in concentrated NaOH are prepared. Then, the solutes are acidified with concentrated HCl, HNO₃ and/or H₂SO₄ at pH 9.5–4.5. Physico-chemical investigations indicate that molybdate(VI) anions are strongly adsorbed onto in situ-precipitated pseudoboehmite from acidic solutions than from basic solutions. The maximum adsorption % of ⁹⁹Mo (167 mg Mo/g matrix dried at 50 ℃) is achieved from the nitrate solution at pH 5.5. Separation of ^99mTc from the corresponding gel matrix with physiological saline solution exhibits high elution yield with a narrow elution profile and radionuclidic, radiochemical and chemical purity indices comparable with ^99mTc eluates from ⁹⁹Mo/^99mTc generators prepared by loading alumina with fission ⁹⁹Mo.