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Due to their properties, humic acids (HA) can interact with macro- and micronutrients and retain plant nutrients in the soil profile. The aim of the presented work was to develop a new integrated 4-step process for the isolation of humic acids from peat with their simultaneous enrichment in macronutrients. The study demonstrated the possibility of replacing traditional solutions used in the extraction of humic acids with solutions that are a source of macronutrients. For the alkaline extraction step, a process assisted with ultrasound was implemented, which allowed to increase the efficiency of humic acids isolation. Optimization of this step has shown that, with the application of ultrasound in the new procedure, it is possible to obtain the humic acids isolation efficiency of more than 60%. The qualitative analysis of the products obtained confirmed the presence of structures characteristic of humic acids, including key functional groups.

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The aim of this study was to evaluate the possibilities of using humic acids obtained from lignite in modern water treatment. The humic acids (HAs) were extracted from polish deposit of lignite – Sieniawa Lubuska by alkaline extraction using for this purpose following extractants: 0.1 M NaOH – HAs SN0.1 and 0.1 M Na4P2O7 – HAs SP0.1. In order to assess the impact of extractant on the sorption properties of the examined humic acids, their specific surface area and the content of active functional groups were determined. Thermo-oxidative behavior of examined humic substances was investigated employing the thermal analysis. The humic acids obtained from lignite were characterized also by 13C NMR spectroscopy. In addition to demonstrate the potential of examined humic acids as a low-cost reactive barrier material for environmental protection applications of toxic metals, sorption of Cr(VI) on the HAs was carried out using a batch method. The structure of obtained humic acids was undoubtedly influenced by the type of extractants used for their isolation. In structure of humic acids derived from lignite the aliphatic connections were dominated. Their participation in HAs obtained by using 0.1 M NaOH amounts to 78.9% and 58.5% for sample obtained using 0.1 M Na4P2O7. The highest content of all acidic functional groups - referred to total acidity (TA) is characterized by HAs obtained by extraction with 0.1 M Na4P2O7 and it was 7.69 mmol/g. In lignite humic acids the carboxylic groups, assigned to peak in the range of 160–190 ppm of 13C NMR spectra constituted for HAs SP0.1 – 3.54% and 2.40% for HAs SN0.1. The specific surface area for all humic acids samples was high from 370.0 to 394.4 m²/g and correlate with the results of humic acids acidity. The sorption of Cr(VI) on the surface of HAs depends strongly on the pH and Cr(VI) sorption increased with a decreasing pH. It was observed that the removal efficiency of Cr(VI) was the highest for SP0.1 and decreased from 79.8% to 66.5% with the rise of pH from 2 to 5. Therefore and because of the highly developed specific surface area of examined humic acids as well as the presence of hydrophilic functional groups resulting in their specific sorption and ion exchange properties can be an attractive and inexpensive option in the water treatment. [ABSTRACT FROM AUTHOR]