Humic substances

Humic substances are natural substances (mixtures of organic materials) present in soil and kaustobiolites (peat, brown coal, and lignite). As an important component of soil and natural humus, they are formed by bio-chemical transformations (decomposition) of organic, particularly plant, residues. The structure of humic acids is very varied, depending not only on their origin and deposit, but also on the date of sampling since humic acids behave like live organisms; their structure changes under suitable conditions. This cycle of structure transformation is an important part of soil-forming processes.

Humic substances are mixtures of humines (water insoluble), humic acids (alkali soluble but acid insoluble), fulvic acids (remain soluble in acid medium), and humatomelic acids (alcohol soluble). In our products, 97-98% of humic substances are formed of humic acids and 2-3% fulvis acids. The low content of fulvic acids (FA) favours the high content of humic acids (HA). In general, FA in soil is considered a less valuable constituent of humus than HA (according to Schachtschabel P. and co-authors: Lehrbuch der Bodekunde, Ferdinand Enke Verlag, Stuttgart 1992).

Humic acids (HA) and fulvic acids (FA) are substances with a wide range of molecular weights (2,000-200,000 grams per mol). They contain three-dimensional cross-linked molecules, the centre of which is an aromatic nucleus containing also oxygenous and nitrogenous heterocycles. To this nucleus are linked aliphatic chains with a rich content of various functional groups - carboxylic and hydroxylic acids that have not yet been completely identified.

Molecular weight of humic acids ranges between 10,000 and 200,000 grams per mol. Fulvic acids are less aromatic and contain more oxygenous groups (carboxyls) and less nitrogen. Their molecular weight ranges between 2,000 and 8,000 grams per mol. They remain soluble in acid medium.

The varied structure of humic acids and content of highly diverse functional groups make these substances very worthwhile study material for many research workplaces. The structure particularly accounts for many very interesting properties of humic acids, e.g. spectral, colloidal, electrochemical, ion-exchangeable, and absorbing ones. Humic acids are capable of absorbing heavy metals by forming complexes with functional groups (COOH, C=O, and -OH) that are bound on the surface of humic acids. Utilization of humic acids in the wide spectrum of industries is a subject for further research and development.