Ultrasound-Assisted Extraction of Humic Substances from Peat: Assessment of Process Efficiency and Products’ Quality

Abstract

Results of efficiency of obtaining humic substances (HSs) from peat in traditional alkaline extraction (TAE) and ultrasound-assisted alkaline extraction (UAAE) are presented. The influence of the duration of the process and ultrasound intensity on the efficiency of extraction of humic acids (HAs) and fulvic acids (FAs) extraction was determined. The composition of the fulvic acid fraction was examined depending on the type of eluent used. Fulvic acids were divided into fractions using columns packed with DAX-8 resin. For this process, 0.1 M NaOH and 0.5 M NH3∙H2O were used as eluents. For the quality assessment of specific fulvic acids fractions, spectroscopic methods (UV-Vis and FTIR) were used. Ultrasound had a positive effect on HS extraction efficiency, especially in increasing the amount of a desired hydrophobic fraction of fulvic acids (HPO). However, a negative effect of the excessive prolongation and ultrasound intensity (approximately 400 mW∙cm−2) on the extraction efficiency of HPO eluted with 0.1 M NaOH solution was observed. Using peat as a raw carbon material for the HS extraction process can be used as an alternative industrial application of peat. UAAE may be considered as an alternative method to TAE, which provides a higher efficiency in HS isolation from peat.

Humic Substances as a Versatile Intermediary

“…In natural systems, HSs interact with microbial communities, dissolved natural organic matter, clays and minerals to inactivate and degrade human-made synthetic toxins (pesticides, polycyclic aromatic hydrocarbons, polychlorinated aliphatic hydrocarbons, petroleum) and deactivate toxic metals (arsenic, mercury, cadmium) [102]. FA can be used to bind heavy metal ions from soil or water because of their high affinity towards metal ions and unique chemical spatial structure [103][104][105][106]. The interactions of HSs with toxic pollutants mainly consist of absorption, binding, association, sequestration and entrapment of the toxic molecule by the massive humic molecules [102].…”

Ultrasound‐Assisted Synthesis of Humic‐Silica Composites by the Isolation of Humic Substances from Peat and Lignite

“…This type of experimental design is considered an RSM model that was characterized by high calculation efficiency. [36] The number of experiments that were required to create the experimental matrix based on BBD can be defined by the following Equation (1): [37] E ¼ 2 � kðkÀ 1Þ þ C 0 (1) Where E is the number of experiments, k is the number of independent parameters, and C 0 is the number of central points. In the present study, the concentration of silicate extractant (X A ), process temperature (X B ) and ultrasound-assisted extraction time (X C ) were chosen as independent variables, and the isolation efficiency of humic substances was chosen as response.…”

“…The first of them defined HS as macromolecular compounds with polymeric structures, and the second considered humic substances as heterogeneous mixtures of small molecules, which through weak interaction form supramolecular structures. [1,2] Generally, humic substances can be divided into fractions that differ in solubility in different pH ranges. The main step of the procedure for the isolation of humic substances includes the alkaline extraction from natural raw materials such as peat, lignite, leonardite, sediments, or compost.…”

The Effect of Sodium Humate Feed Additives in Diets for Holstein Breed Heifers

“…NaHum extraction is a promising approach for producing this valuable humic acid derivative. The use of an alkaline solution to extract NaHum is a relatively simple and environmentally friendly process that can be easily scaled up for industrial production, making it an attractive option for applications such as animal breeding and dietary supplements [63]. Additionally, NaHum production from freshwater sapropel at an industrial scale has real potential because the raw material is abundant and the extraction process is relatively simple and cost-effective [64].…”