Mechanism and Interaction of Humic Substance and Crystalline/(SRO) Short-Ranged Ordered Al and Fe (oxy)Hydroxide Mineral Colloids.

It is believed that association of organic matter with minerals provides physically protection against rapid microbial decay, because of sorptive preservation and having a limit to accessibility to avoid labile organic molecules decomposed. Although adsorption of humic substance onto mineral surfaces has been investigated over the decades, however, the mechanisms governing the adsorption of humic substance (HS) are still not well understood. The objective of this study was to investigate the adsorption and mechanisms between humic aicd and typical mineral colloids (clay minerals, crystalline and SRO Al and Fe (oxy)hydroxides and oxides). And the turnover and stability of organic carbon as influenced by these mineral colloids which differently in their atomic bonding, structural configuration, and surface chemistry. The pH results indicated that adsorption of HS onto metal oxide surfaces increases with decreasing pH value, that was pH 4>pH 6>pH 8. The reason may because of the pKa values of most abundant carboxylic acids and the maximum adsorption at pH 4.3 to 4.7. It reasonably seems that ligand exchange via surface complexation of negatively charged functional groups of OM (e.g., carboxyl and phenolic OH groups) may be the predominant binding mechanism. The FT-IR spectra also prove that. Therefore, once we know more about the interactions between minerals and HS, we can protect more carbon storage and retard CO2, CH4, DOC, POC and DIC emission or release.