A hydrothermal process to turn waste biomass into artificial fulvic and humic acids for soil remediation

Abstract

A novel preparation protocol for synthetic, look-a-like humic substances (i.e., fulvic and humic acids) simulating geochemical processes through hydrothermal reaction is presented, with crude waste biomass as an omnipresent and universal precursor. The chemical nature of the organic scaffold and the type and abundance of oxygen-containing functional groups of the synthetic humic substances (A-FA and A-HA) are revealed by a series of examinations. Results from EA, XPS analyze, FTIR spectra and NMR technology matched well each other, suggesting high similarity on chemical structure (abundant aromatic frameworks) and contents (e.g. N and S elements) in both humic acids. Pyrolysis-gas-chromatography/mass spectrometry (Py-GC/MS) analysis is employed on the organic structure and is directly compared to extracted natural humic matter from black soils (Harbin, China). Dehydrated carbohydrates and their condensates with low molecular weight that are rich in oxygen are the main structural components of the artificial fulvic acids, while aromatic structures and aliphatic side chains are almost absent. Aromatics (7.43%) and in some cases long-chain aliphatics (7.15%) are more prominent in the A-HA sample. The combination of the diverse analytical techniques not only allows a better understanding of artificial fulvic and humic acids, but also supports the high similarity to natural humic substances in structure and morphology. As the technology can be easily scaled and is comparable cheap, the as obtained products can be discussed to rehabilitate used up farm land.