Interaction of Hg(II) with kaolin-humic acid complexes

Clay Minerals ◽  
2004 ◽  
Vol 39 (1) ◽  
pp. 35-45 ◽  
Author(s):  
M. Arias ◽  
M.T. Barral ◽  
J . Da Silva–Carvalhal ◽  
J .C. Mejuto ◽  
D. Rubinos
Keyword(s):  
Organic Matter ◽  
Humic Acid ◽  
Dissolved Organic Matter ◽  
Equilibrium Concentration ◽  
Soluble Complex ◽  
Ph Values ◽  
Subsurface Waters ◽  
Ph Range ◽  
Surface And Subsurface Waters ◽  
Reduced Risk

AbstractThe adsorption and desorption of Hg(II) by humic acid (HA) previously adsorbed on kaolin was studied. In the range of HA concentration investigated (0.0 –26.9 mg g–1), the Hg(II) adsorption capacity of kaolin at pH 4 is enhanced by the presence of HA. For the complexes with the highest HA concentration and for low Hg(II) initial concentrations, adsorption was lower, i.e. as HA concentration on the complexes increases, Hg(II) equilibrium concentration also increases. This behaviour is due to the increasing presence of dissolved organic matter as the HA concentration on the complexes increases. The dissolved organic matter is able to form a soluble complex with Hg, thus decreasing adsorption. Hg(II) adsorption from a 2.5×10–5 MHg(II) solution was influenced by pH. For kaolin, a pHmax (pH where maximum adsorption occurs) of 4.5 was observed. At pH values >pHmax retention decreased with increasing pH. This same behaviour was observed for the kaolin- HA complex containing the lowest HA concentration (6.6 mg g –1). For the other kaolin-HA complexes there was little effect of pH on Hg(II) adsorption between pH 2.5 and pH 6.5. The presence of HA increased the adsorption of Hg(II) on kaolin all along the pH range studied. Desorption experiments showed that the amount of Hg(II) desorbed was quite low (<1%) for all the HA and Hg(II) concentration range studied, except for the kaolin at acid pH (pH 2.5) where the Hg(II) released was >50% of Hg(II) previously adsorbed. The presence of HA dramatically reduced this percentage of desorption to values of <3%, indicating reduced risk of toxicity problems in surface and subsurface waters. The addition of Cu(II) did not favour any Hg(II) desorption, even though Cu exhibits a strong affinity for organic matter.

scholarly journals Uranyl binding to humic acid under conditions relevant to cementitious geological disposal of radioactive wastes

2012 ◽  
Vol 76 (8) ◽  
pp. 3391-3399 ◽  
Author(s):  
A. Stockdale ◽  
N. D. Bryan
Keyword(s):  
Organic Matter ◽  
Humic Acid ◽  
Dissolved Organic Matter ◽  
Equilibrium Dialysis ◽  
Radioactive Wastes ◽  
Experimental Results ◽  
Uranyl Ions ◽  
Geological Disposal ◽  
Ph Range ◽  
Competing Ions

AbstractFew studies have sought to investigate the potential for dissolved organic matter (DOM) to bind (and thus potentially transport) radionuclides under the high pH regimes that are expected in cementitious disposal. We have used equilibrium dialysis to investigate uranyl binding to humic acid over a pH range of ∼10 to 13. The experimental results provide evidence that DOM can bind uranyl ions over this pH range, including in the presence of competing ions. There is a general decrease in binding with increasing pH, from ∼80% of total uranyl bound at pH 9.8 to ∼10% at pH 12.9. Modelling of the system with WHAM/Model VII can yield representative results up to pH ∼10.5.

scholarly journals Treatability of organic matter derived from surface and subsurface waters of drinking water catchments

Chemosphere ◽  
2016 ◽  
Vol 144 ◽  
pp. 1193-1200 ◽  
Author(s):  
John Awad ◽  
John van Leeuwen ◽  
Joel Liffner ◽  
Christopher Chow ◽  
Mary Drikas
Keyword(s):  
Drinking Water ◽  
Organic Matter ◽  
Subsurface Waters ◽  
Surface And Subsurface Waters ◽  
Water Catchments

Molecular Changes in Dissolved Organic Matter After Soil Rewetting

2021 ◽  
Author(s):  
Alice Orme ◽  
Simon Benk ◽  
Markus Lange ◽  
Christian Zerfaß ◽  
Georg Pohnert ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Mass Spectrometry Analysis ◽  
Microbial Decomposition ◽  
Molecular Changes ◽  
Spectrometry Analysis ◽  
Subsurface Waters ◽  
High Production ◽  
High Concentrations ◽  
Over Time

&lt;p&gt;The intensity and occurrence of droughts is projected to increase due to climate change. Dried soils release high concentrations of dissolved organic matter (DOM) into subsurface waters when they are rewet, the so-called rewetting peak. To more accurately predict the role of rewetting of soils after drought on the carbon cycle in a changing climate, it is important to understand the processes behind this DOM release.&lt;/p&gt;&lt;p&gt;The DOM rewetting peak origin is disputed between soil organic matter (SOM) from breakdown of soil particles; accumulated root exudates; and microbial release due to a change in osmotic potential through osmolytes or cell bursting. To better understand the origin of the rewetting DOM peak, we took a rewetting series of soil water samples from different vegetation types between December 2018 and April 2019 for targeted and untargeted metabolomics. Initial results using untargeted ultrahigh-resolution mass spectrometry analysis revealed a clear temporal trend, indicating that vegetation-independent molecular changes occur following rewetting. An increase in O/C and a decrease in H/C over time was observed which is attributed to microbial decomposition, supported by a decrease in m/z over time. We also observed an increase in the content of lipidic compounds (R &gt; 0.6) following rewetting. This indicates that cells do not burst upon rewetting and, over time, microbial activity increases, suggesting that the DOM rewetting peak is caused by a lack of decomposition, rather than a high production, of organic matter.&lt;/p&gt;

scholarly journals Spectroscopic detection of a ubiquitous dissolved pigment degradation product in subsurface waters of the global ocean

2012 ◽  
Vol 9 (7) ◽  
pp. 2585-2596 ◽  
Author(s):  
R. Röttgers ◽  
B. P. Koch
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Degradation Product ◽  
Oxygen Minimum Zone ◽  
Particulate Fraction ◽  
Deep Chlorophyll Maximum ◽  
Subsurface Waters ◽  
Minimum Zone ◽  
Absorption Shoulder ◽  
Oxygen Minimum

Abstract. Measurements of light absorption by chromophoric dissolved organic matter (CDOM) from subsurface waters of the tropical Atlantic and Pacific Oceans showed a distinct absorption shoulder at 410–415 nm. This indicates an underlying absorption of a pigment whose occurrence is partly correlated with the apparent oxygen utilization (AOU) but also found in the deep chlorophyll maximum. A similar absorption maximum at ~415 nm was also found in the particulate fraction of samples taken below the surface mixing layer and is usually attributed to absorption by respiratory pigments of heterotrophic unicellular organisms. In our study, fluorescence measurements of pre-concentrated dissolved organic matter (DOM) samples from 200–6000 m confirmed a previous study suggesting that the absorption at ~415 nm was related to fluorescence at 650 nm in the oxygen minimum zone. The absorption characteristics of this fluorophore was examined by fluorescence emission/excitation analysis and showed a clear excitation maximum at 415 nm that could be linked to the absorption shoulder in the CDOM spectra. The spectral characteristics of the substance found in the dissolved and particulate fraction did not match with those of chlorophyll a degradation products (as found in a sample from the sea surface) but can be explained by the occurrence of porphyrin pigments from either heterotrophs or autotrophs. Combining the observations of the fluorescence and the 415-nm absorption shoulder suggests that there are high concentrations of a pigment degradation product in subsurface DOM of all major oceans. Most pronouncedly we found this signal in the deep chlorophyll maximum and the oxygen minimum zone of tropical regions. The origin, chemical nature, turnover rate, and fate of this molecule is so far unknown.

scholarly journals Adsorption of Triclocarban on Pristine and Irradiated MWCNTs in Aqueous Solutions

2019 ◽  
Vol 70 (8) ◽  
pp. 2835-2842 ◽  
Author(s):  
Ion Ion ◽  
Raluca Madalina Senin ◽  
Georgeta Ramona Ivan ◽  
Sanda Maria Doncea ◽  
Michael Patrick Henning ◽  
...  
Keyword(s):  
Experimental Data ◽  
Organic Matter ◽  
Humic Acid ◽  
Aqueous Solutions ◽  
Natural Organic Matter ◽  
Environmental Conditions ◽  
Sorption Process ◽  
Ph Values ◽  
Different Temperatures ◽  
The Impact

The adsorption of triclocarban was investigated on pristine and irradiated MWCNTs, at different temperatures, in aqueous synthetic samples at different pH values and for different concentrations of humic acid (HA) from natural organic matter. Commonly used models of the adsorption isotherms, Freundlich and Langmuir were selected to fit the experimental data. The effects of TCC concentration, of the temperature and of the concentration of humic acid from natural organic matter were tested to study the impact of the environmental conditions over the sorption process.

scholarly journals Distribution and habitat conditions of the phytocoenoses of Sphagnum denticulatum Bridel and Warnstorfia exannulata (B., S. and G.) Loeske in Polish Lobelia lakes

2011 ◽  
Vol 73 (3) ◽  
pp. 255-262 ◽  
Author(s):  
Marcin Szańkowski ◽  
Stanisław Kłosowski
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Floristic Composition ◽  
Electrolytic Conductivity ◽  
Lower Amount ◽  
Aquatic Communities ◽  
Total N ◽  
Ph Values ◽  
Acidic Waters ◽  
Isoetes Lacustris

Phytosociological and habitat studies of <em>Sphagnum denticulatum</em> and <em>Warnstorfia exannulata </em>phytocoenoses from Polish <em>Lobelia</em> lakes have been conducted. The present results were compared with data on <em>Isoetes lacustris </em>community. It is demonstrated that both communities of mosses are distinct with respect to their floristic composition. Moreover, they differ significantly from the patches of <em>I. lacustris </em>with regard to many properties of water and substrates. The phytocoenoses of <em>S. denticulatum </em>are associated with softer waters, poorer in Ca<sup>2+</sup>, Na<sup>+</sup>, NH<sub>4</sub><sup>+</sup> and dissolved organic matter, but richer in total Fe than those of <em>I. lacustris</em>. They are also distinguished by lower values of electrolytic conductivity. The substrates they inhabit are more strongly hydrated and richer in organic matter, total N, dissolved SiO<sub>2</sub>, Ca<sup>2+</sup> and Na<sup>+</sup>, but poorer in PO<sub>4</sub><sup>3-</sup>. The <em>W. exannulata</em> phytocoenoses are also confined to softer waters with lower Ca<sup>2+</sup>, NH<sub>4</sub><sup>+</sup> and dissolved organic matter contents than those of <em>I. lacustris</em>. Their substrates are more strongly hydrated and have higher contents of organic matter, total N and Na<sup>+</sup> but lower amounts of PO<sub>4</sub><sup>3-</sup>. In addition the waters of <em>W. exannulata </em>phytocoenoses are characterized by higher pH values and lower concentration of dissolved SiO<sub>2</sub>. The substrates are less acidic and richer in NO<sub>3</sub><sup>-</sup>, but poorer in total Fe. The differences between the habitats of the <em>S. denticulatum </em>and <em>W. exannulata</em> phytocoenoses are also distinct. The former inhabit more acidic waters, richer in dissolved SiO<sub>2</sub> and total Fe, but with lower values of electrolytic conductivity and concentration of Na<sup>+</sup>. Their substrates are distinguished by higher contents of organic matter and Ca<sup>2+</sup>, as well as by lower amount of NO<sub>3</sub><sup>-</sup>. In view of the fact that the above phytocoenoses of mosses are distinct with respect to their floristic composition and are associated with specific habitats in which they form dense mats close to the bottom of the lake, they should be classified as distinct associations (Sphagnetum denticulati and Warnstorfietum exannulatae) in the system of aquatic communities (Class: Utricularietea intermedio-minoris).

scholarly journals Humic Acid Extracts Leading to the Photochemical Bromination of Phenol in Aqueous Bromide Solutions: Influences of Aromatic Components, Polarity and Photochemical Activity

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 608
Author(s):  
Hui Liu ◽  
Yingying Pu ◽  
Xiaojun Qiu ◽  
Zhi Li ◽  
Bing Sun ◽  
...  
Keyword(s):  
Organic Matter ◽  
Humic Acid ◽  
Dissolved Organic Matter ◽  
Chemical Properties ◽  
Photochemical Activity ◽  
Simulated Solar Light ◽  
Geochemical Cycle ◽  
Reactive Halogen Species ◽  
Aromatic Components ◽  
Bromide Solutions

Dissolved organic matter (DOM) is considered to play an important role in the abiotic transformation of organobromine compounds in marine environment, for it produces reactive intermediates photochemically and is recognized as a significant source of reactive halogen species in seawater. However, due to the complex composition of DOM, the relationship between the natural properties of DOM and its ability to produce organobromine compounds is less understood. Here, humic acid (HA) was extracted and fractionated based on the polarity and hydrophobicity using silica gel, and the influences of different fractions (FA, FB and FC) on the photochemical bromination of phenol was investigated. The structural properties of HA fractions were characterized by UV-vis absorption, Fourier transform infrared spectroscopy and fluorescence spectroscopy, and the photochemical reactivity of HA fractions was assessed by probing triplet dissolved organic matter (3DOM*), singlet oxygen (1O2) and hydroxyl radical (•OH). The influences of HA fractions on the photo-bromination of phenol were investigated in aqueous bromide solutions under simulated solar light irradiation. FA and FB with more aromatic and polar contents enhanced the photo-bromination of phenol more than the weaker polar and aromatic FC. This could be attributed to the different composition and chemical properties of the three HAs’ fractions and their production ability of •OH and 3DOM*. Separating and investigating the components with different chemical properties in DOM is of great significance for the assessment of their environmental impacts on the geochemical cycle of organic halogen.

scholarly journals Effect of Pyrolysis Temperature on the Characterisation of Dissolved Organic Matter from Pyroligneous Acid

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3416
Author(s):  
Genmao Guo ◽  
Qingqing Wang ◽  
Qing Huang ◽  
Qionglin Fu ◽  
Yin Liu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Humic Acid ◽  
Dissolved Organic Matter ◽  
Spectroscopic Analysis ◽  
Pyrolysis Temperature ◽  
Organic Carbon Content ◽  
Pyroligneous Acid ◽  
Temperature Ranges ◽  
Gas Chromatography Mass Spectroscopy ◽  
By Products

Dissolved organic matter (DOM) greatly influences the transformation of nutrients and pollutants in the environment. To investigate the effects of pyrolysis temperatures on the composition and evolution of pyroligneous acid (PA)-derived DOM, DOM solutions extracted from a series of PA derived from eucalyptus at five pyrolysis temperature ranges (240–420 °C) were analysed with Fourier transform infrared spectroscopy, gas chromatography–mass spectroscopy, and fluorescence spectroscopy. Results showed that the dissolved organic carbon content sharply increased (p < 0.05) with an increase in pyrolysis temperature. Analysis of the dissolved organic matter composition showed that humic-acid-like substances (71.34–100%) dominated and other fluorescent components (i.e., fulvic-acid-like, soluble microbial by-products, and proteinlike substances) disappeared at high temperatures (>370 °C). The results of two-dimensional correlation spectroscopic analysis suggested that with increasing pyrolysis temperatures, the humic-acid-like substances became more sensitive than other fluorescent components. This study provides valuable information on the characteristic evolution of PA-derived DOM.

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