Batch sorption experiments were used to determine the adsorption isotherms of three natural organic matter (NOM) samples of varying amphiphilic character on alumina. Solid-state 13C DPMAS NMR was used to characterize the dissolved and adsorbed NOM components. The data shows similar adsorption isotherms but differences in the carbon-types that were sorbed and the NMR relaxation time of the sorbed fractions. Aromatic carbon was preferentially adsorbed in the sample that was the strongest amphiphilic character and underwent a pronounced decrease in NMR relaxation time at both low and high surface coverage, the aromatic carbon of the intermediate-strength amphiphile sample was preferentially adsorbed only at low surface coverage and its aliphatic carbon preferentially adsorbed at high surface coverage. It demonstrated limited changes in NMR relaxation time at low surface coverage. The aliphatic carbon of weakest amphiphile was preferentially adsorbed at low as well as at high surface coverage. Observation of selective adsorption based on changes in 13C NMR carbon-type distributions are dependent on the relaxation times (T1) used to acquire the spectra.

Use of NMR carbon-type distributions to assess the extent of preferential adsorption of natural organic matter components

253rd National Meeting (2017)

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