The Effect of Supramolecular Humic Acids on the Diffusivity of Metal Ions in Agarose Hydrogel

Abstract

Humic acids are known as natural substances of a supramolecular nature. Their self-assembly ability can affect the migration of heavy metals and other pollutants in nature. The formation of metal-humic complexes can decrease their mobility and bioavailability. This study focuses on metal ions diffusion and immobilization in humic hydrogels. Humic acids were purchased from International Humic Substances Society (isolated from different matrices—peat, soil, leonardite, water) and extracted from lignite mined in Czech Republic. Copper(II) ions were chosen as a model example of reactive metals for the diffusion experiments. The model of instantaneous planar source was used for experimental data obtained from monitoring the time development of copper(II) ions distribution in hydrogel. The effective diffusion coefficients of copper(II) ions showed the significant dependence on reaction ability of humic hydrogels. Lower amounts of the acidic functional groups caused an increase in the effective diffusion coefficient. In general, diffusion experiments seem to act as a valuable method for reactivity mapping studies on humic substances.

Water Recovery from Wastewater by Hydrogels

“…In most solutions with different pollutants, the hydrogels exhibited similar swelling ratios (around 460 g/g), except for humic acid, which had a much lower swelling ratio ranging from 131 to 250 g/g (Figure a). Humic acid, a natural complex formed from decomposed plant and animal matter, contains supramolecular binding and macromolecules within its structure . During water absorption, humic acid molecules enter the interior of the hydrogel, binding to the hydrophilic groups.…”

“…Humic acid, a natural complex formed from decomposed plant and animal matter, 22 contains supramolecular binding and macromolecules within its structure. 23 During water absorption, humic acid molecules enter the interior of the hydrogel, binding to the hydrophilic groups. This interaction ultimately limits further water absorption and swelling of the hydrogel.…”

Heavy Metal Contamination in Soil: Implications for Crop Resilience and Abiotic Stress Management

“…Humic and fulvic acids, significant components of soil organic matter, can significantly influence plants' uptake of toxic metals/metalloids. They can form complexes with metals, affecting their solubility and bioavailability [57][58][59][60][61][62][63][64].…”

“…Humic substances, including humic and fulvic acids, can significantly affect the environmental behavior of metal pollutants through processes, such as ion exchange and physical adsorption [60]. They can form complexes with toxic metals/metalloids, altering their mobility and bioavailability [57,58,61]. For instance, forming metal-humic complexes can decrease mobility and bioavailability [61].…”

Organic matter in the pest and plant disease control: a meta-analysis

“…HS was the organic matter source that showed the greatest effectiveness (74.9%) in plants pest and disease control according to model proposed by Sukamto [133], and suggesting their potential role as biotic elicitors in stimulating defense pathways. Humic substances comprise humic and fulvic acids and consist of natural molecules of amphiphilic nature able to generate supramolecular assemblies in solution [134,135]. HS are also widely recognized as biostimulants as they promote plant growthrelated processes, enhance plant nutrient uptake and use efficiency, induce resistance and tolerance to abiotic stress, and improve the quality of crop-derived products when applied in small amounts.…”