Impact of Hydrofluoric Acid Treatment on Humic Acid Properties Extracted from Organic Soils and an Organic Amendment: A Technical Evaluation

Abstract

The chemical and physical characteristics of humic acids (HA) may differ depending on their source, and the ideal extraction method should not modify the characteristics of HA. Hydrofluoric acid (HF) is often used in HA extraction methods to remove inorganic substances that are often present in the sample in addition to the organic molecules of interest. Organic soils contain up to 90% of organic matter and some may think that the necessity of the HF treatment is not crucial when extracting HA from organic soils. In this study, HA were extracted from turkey litter compost (TLC), an agricultural organic soil (AOS) and a riparian soil (RS), and the impact of HF on the properties of the extracted HA was assessed. HF decreased the ash content and the concentration of inorganic components in extracted materials, especially in the HA from RS, which had higher concentrations of aluminosilicates and amorphous Si. For TLC, no significant difference in either the total charge or charge distribution was observed with HF treated samples compared to untreated samples, while the HF treatment decreased the proton binding capacity at alkaline pH (≥7) in the HA from the two soils. We assume that aluminosilicates, amorphous Si and iron oxides left in the samples interacted with protons at alkaline pH, thus increasing the proton binding capacity. Therefore, HF treatment should be included when samples containing these mineral constituents even for materials rich in organic matter. Core Ideas Hydrofluoric acid did not affect functional group distribution or C concentration in humic acids. Proton binding capacity at alkaline pH of soil humic acids decreased after hydrofluoric acid treatment. Hydrofluoric acid did not affect characteristics of humic acids extracted from turkey litter compost. Humic acids from turkey litter compost had lower proton binding capacity than those from soils.

Validation and comparisons of NaOH and Na4P2O7 extraction methods for the characterization of organic amendments

“…(2019). Similarly, a relative increase in the carboxyl groups after HF/HCl treatment was observed in other studies (e.g., Audette et al., 2019; Botero et al., 2018). These observations are likely due to the removal of paramagnetic ions such as Fe and Mn by the HCl treatment as these metals are known to complex with carboxyl and phenolic groups; NMR measurements are sensitive to paramagnetic species and signal strengths can be reduced by their presence (Table 1).…”

“…A relative increase in the phenolic groups in soil sample after the HCl treatment was also observed in the study by Vinci et al (2019). Similarly, a relative increase in the carboxyl groups after HF/HCl treatment was observed in other studies (e.g., Botero et al 2018;Audette et al 2019). These observations are likely due to the removal of This article is protected by copyright.…”

Attenuated Total Reflection (ATR) Micro-Fourier Transform Infrared (Micro-FT-IR) Spectroscopy to Enhance Repeatability and Reproducibility of Spectra Derived from Single Specimen Organic-Walled Dinoflagellate Cysts

“…74 The effect of HF most probably will be removal of minerals sorbed or sticking to the cysts. 75 The concentrations of the chemicals used in this study as well as the reaction temperatures are considered to be too low to induce Maillard reactions, which produce insoluble polymers. The fingerprint regions of the ATR spectra of T. applanatum from Olhão Port, Algarve, Portugal (no palynological maceration), and Xiamen Bay (palynological maceration) show only minor differences in terms of band positions and intensities, which could possibly reflect environmental factors, intraspecific chemical variations and/or (extra)cellular materials sticking to the cysts.…”

Evidence for the formation of fused aromatic ring structures in an organic soil profile in the early diagenesis

“…HA from three depths was dialyzed with MilliporeÒ nanopure water until the EC reached 1 μs -1 . HA isolated from the CS was treated with 0.2 M HF 32 . After dialysis, samples were freeze-dried and used for the NMR spectroscopy experiments.…”