The metal oxide-facilitated transformation of polyphenols and amino acids to humic substances (HS) is an essential process in soil and compost maturing processes. The objective of this research was to examine the specific roles of MnO2 and O2 in the formation of HS by oxidative polymerization between catechin (a polyphenol) and glycine (an amino acid). The results demonstrated that large amounts of fulvic acid (FA) and humic acid (HA) formed by O2 only, MnO2 itself only led to a small amount of HS generated, while the presence of both O2 and MnO2 significant enhanced HA formation, demonstrating their synergistic effects. The size of HA only increased in the presence of MnO2. Two-dimensional correlation spectroscopy results suggested that the sequence of the formation of HA functional groups was: C–OH in carboxylic acids&gt;C-O in phenolic-OH&gt;amide II and aromatic C−C&gt;amide and carboxylate C=O&gt;COO- &gt;NH&gt;hydrogen bonds. Finally, XPS spectra of the residual MnO2 showed that the Mn(IV) content decreased from &gt;99% to 89.98% and 80.89% while the Mn(III) content increased from &lt;0.1% to 10.02% and 15.07% for the humification in MnO2 with and without O2, respectively, suggesting the role of MnO2 as both a catalyst and a direct oxidant. The results offered new insights into the abiotic humification process and can help developing treatment technologies for bio-wastes.

Roles of oxygen and Mn(IV) oxide in abiotic formation of humic substances by oxidative polymerization of polyphenol and amino acid

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.