Molybdenum isotopic fractionation during ferrite oxide adsorption: Experimental evaluation

  • 李 昇憲

學生論文: Master's Thesis

摘要

Abstract With the advance of MC-ICP-MS it has become possible to measure mass-dependent variations in the isotopic compositions of many transition metals to previously unattainable levels of precision The Molybdenum (Mo) isotopic fractionation has been applied successfully as a redox proxy in marine environments Mo occurs as Mo (VI) anion molybdate MoO42- in seawater and Mo4-xSx in marine sediments The latter species were converted from MoO42- and MoS42- and finally to form other sulfides The Mo isotopic composition (δ97/95Mo) in seawater is ~2? heavier than of ferromanganese crusts or nodules as a function of redox states However under the reducing environment Mo4-xSx was sequestered in suboxic or anoxic sediments with δ97/95Mo value of 0~1 6? Also we presented Mo isotope determination method using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS Neptune) with a combined standard-sample bracketing (SSB) procedures and empirical external normalization (EEN) for mass bias correction during measurement T he chemical separation using AG 1-X8 resin was applied to purify Mo from potential interference elements (Zr and Rb) In summary the adsorption rate increased with decreasing pH and the optimal adsorption occurred at pH 2 75 and the adsorption rate could be up to 95% Our results suggested that the isotopes achieved exchange equilibrium between solid and aqueous phased after 24h The lighter isotope was preferentially adsorbed onto the Fe3O4 particles and resulted in an isotopic heavier Mo in solution The δ 97/95Mo under the range of pH 1 85 to 7 53 has relative values from 0 16 to -1 11? We proved that not only the differing redox state could influence the fractionation factors but the differing pH could significantly impact on the fractionation factors The significance of pH condition on Mo isotope fractionation was evident and the driven factor is predominated controlled by the Mo chemical species
獎項日期2014 八月 18
原文English
監督員Chen-Feng You (Supervisor)

引用此

Molybdenum isotopic fractionation during ferrite oxide adsorption: Experimental evaluation
昇憲, 李. (Author). 2014 八月 18

學生論文: Master's Thesis