Potentiometric titration of humic acids

Khil’ko, S. L.; Kovtun, Anna; Рыбаченко, В. И.

doi:10.3103/s0361521911050028

Cited by 19 publications

(12 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…10 Therefore, a similar protocol used to measure carboxyl groups in humic acid was used in this study. The CEC of the soluble biochar molecular fragments in the filtrates was quantified by measuring the carboxyl groups contained in the 10 mL filtrate, using a modified approach as performed by Khil'ko et al (2011) 16 with a potentiometric titration of the filtrates.…”

Section: ■ Introductionmentioning

confidence: 99%

Sustainable Green Chemistry: Water-Soluble Ozonized Biochar Molecules To Unlock Phosphorus from Insoluble Phosphate Materials

Sacko

Feng

Morris

et al. 2022

ACS Agric. Sci. Technol.

View full text Add to dashboard Cite

A dramatic enhancement by a factor of 15 for the production of ozonized biochar molecular products measured as dissolved organic carbon (DOC) was achieved by an innovative biochar ozonization process. The filtrate of the ozonized biochar molecular products contained substantially more carboxyl groups than that of the nonozonized biochar. The ozonized biochar molecules are now identified to be highly potent, even at a ppm DOC concentration level, to "unlock" phosphorus (P) from insoluble phosphate material hydroxyapatite (HA). At a DOC concentration of 600 ppm, the filtrates from the wet-ozonized pine 400 biochar and the dry-ozonized rogue biochar substances were both able to solubilize HA, resulting in a concentration of solubilized phosphorus up to 396.8 ± 28.8 and 339.6 ± 8.5 mg HPO 4 2− /L, respectively. Even at a DOC concentration as low as 10 ppm, the ozonized biochar molecules solubilized up to 8.3 ± 1.1 mg/L of phosphate. At neutralized pH 7, the efficiency in solubilizing phosphate decreased, indicating the importance of the protonic effect. The ozonized biochar organic acids solubilized more phosphate than a hydrochloric acid solution with the same pH, thus showing the applicability of this green chemistry with ozonized biochar molecules to unlock P from insoluble phosphate rock materials. The discovery of ozonized biochar molecules capable of unlocking P is highly relevant to agricultural phosphorus and environmental sustainability on the Earth.

show abstract

Section: ■ Introductionmentioning

confidence: 99%

Sustainable Green Chemistry: Water-Soluble Ozonized Biochar Molecules To Unlock Phosphorus from Insoluble Phosphate Materials

Sacko

Feng

Morris

et al. 2022

ACS Agric. Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…To this end, different solvents (aqueous [21] and non-aqueous [22]) are used by different authors. Some researchers report on indication of different types of oxygen-containing functional groups by different inclination angles and inflections at titration curves obtained in aqueous solution [23,24]. Nonetheless, in most cases, the aims of the studies are to find a total amount of acidic groups in coal matter.…”

Section: Introductionmentioning

confidence: 99%

“…In general, due to the solvation methods of the coal organic matter, the analysed functional groups are primarily located at the coals surface, whereas the internal ones, that are hard to be extracted, are left to remain. Therefore, ion exchange analysis methods allow characterization of total sorption activity of humic acids [24], whereas for coals, these results are not usually applicable for characterization of entire possible activity, but only the surface sorption properties and, consequently, coals' oxidation degree [21,23].…”

Section: Introductionmentioning

confidence: 99%

Development of potentiometric titration method for assessing coals’ oxidation degree

Epshtein¹,

Sokolovskaya²,

Dobryakova³

et al. 2022

View full text Add to dashboard Cite

Oxidation of coal leads to some unwanted consequences, such as losses of products quality and increase in proneness to spontaneous combustion. One of the indicators of coals' oxidation is changing in amount and composition of active functional groups in organic matter. On using a wide number of samples and adjusting the experimental procedure, a method was developed for coals' oxidation degree evaluation by potentiometric titration based on evaluation of contents of total acidic groups (a sum of phenol and carboxyl groups). It was shown that potentiometric titration is not applicable for determination of phenol and carboxyl groups in coals separately. A phenomenon of appearance of two waves at titration curve was connected with absorption of CO 2 from air into the alcohol-alkaline solution. For coals with vitrinite reflectance varying in 2 range of 0.5-0.72 %., total acidic groups amount decrease with rank growth, whereas for higher rank coals such an alteration is less pronounced. It is shown that it is expedient to use the developed method of potentiometric titration together with the petrographic method for determining the oxidation degree. On the basis of the proposed method of coals' oxidation degree determination by potentiometric titration, a National standard of the Russian Federation GOST R 59012-2020 has been introduced. According to it, the oxidation degree is determined by the increase of the total amount of acidic groups -phenolic and carboxyl hydroxyls in coal as compared to the content of total acidic groups in the control sample, which is used as a seam sample of coal taken outside the oxidation zone, or coal taken when laying the pile, or coal received for benefication, sorting or moving.

show abstract

“…It is well known that the utilization of titration data for the determination of dissociation constants is connected with several problems [10,27,28]. Fernandes et al [27] compared the fitting of titration data by two different models and stated that the results were strongly dependent on both the choice of model as well as the experimental conditions (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…titration rate). Khil´ko et al [28] showed that the results of potentiometric titrations and the calculated dissociation constants depend on the titration method, the humic concentration, and the time taken to establish the titration rate. There are other ways to determine the dissociation constants of humic acids, but these methods are rarely utilized.…”

Section: Introductionmentioning

confidence: 99%

New possibility for characterization of dissociation behaviour of supramolecular electrolytes: results obtained for the International Humic Substances Society standard and reference samples by coulometry

Klučáková

2021

Chem. Biol. Technol. Agric.

View full text Add to dashboard Cite

Background Humic substances can be considered as polyelectrolytes with supramolecular character and complicated behaviour in water environment. The fractions of humic substances dissolved in water are the most active ones and determinative for their functioning in nature, where the proton-binding and dissociation ability play a crucial role. The dissociation behaviour of humic and fulvic acids can be affected by different circumstances including their concentration which is directly connected with the molecular organization of humic particles in solution and the accessibility of their ionizable functional groups. This study is focused just on these active fractions and their dissociation behaviour in the dependence on their content in studied system. Results Standards and reference samples of International Humic Substances Society were used. Flow-through coulometry was used to determine the total content of acidic functional groups in fulvic solutions and humic leachates. The amount of dissociated acidic groups was determined on the basis of potentiometry. Several differences between the behaviour of humic and fulvic acids were found. While whole samples of fulvic acids including the weakest functional groups were analysed, only the active dissolved humic fractions containing stronger acidic functional groups were characterized. The fractions containing higher amounts of the weakest functional groups remained insoluble. The dissociation degree of fulvic acids decreased with their increasing content, but a maximum on its concentration dependence obtained for humic acids was observed. Conclusions Two different values of dissociation constants were determined for each sample. The first was determined on the basis of the extrapolation of infinite dilution, second was determined as their average value in the region of high concentrations in which it was constant. Obtained values characterize the functioning of dissolved humic substances from point of view of their dissociation ability. The results obtained by this approach can help to predict the acid–base behaviour of dissolved organic carbon in soil and generally in nature. The acid–base behaviour of dissolved organic carbon depends on its ratio to water. It behaves differently in soil which is dry and in soil which is wet or saturated by water.

show abstract

Potentiometric titration of humic acids

Cited by 19 publications

References 27 publications

Sustainable Green Chemistry: Water-Soluble Ozonized Biochar Molecules To Unlock Phosphorus from Insoluble Phosphate Materials

Sustainable Green Chemistry: Water-Soluble Ozonized Biochar Molecules To Unlock Phosphorus from Insoluble Phosphate Materials

Development of potentiometric titration method for assessing coals’ oxidation degree

New possibility for characterization of dissociation behaviour of supramolecular electrolytes: results obtained for the International Humic Substances Society standard and reference samples by coulometry

Contact Info

Product

Resources

About