U(VI)-Kaolinite Surface Complexation in Absence and Presence of Humic Acid Studied by TRLFS

2007 ◽  
Vol 41 (17) ◽  
pp. 6142-6147 ◽  
Author(s):  
Adéla Křepelová ◽  
Vinzenz Brendler ◽  
Susanne Sachs ◽  
Nils Baumann ◽  
Gert Bernhard
Keyword(s):  
Humic Acid ◽  
Surface Complexation ◽  
Kaolinite Surface

β-Zeolite modified by ethylenediamine for sorption of Th(IV)

2017 ◽  
Vol 105 (6) ◽  
Author(s):  
Liu Peng ◽  
Wu Hanyu ◽  
Yuan Ni ◽  
Yin Zhuoxin ◽  
Pan Duoqiang ◽  
...  
Keyword(s):  
Steady State ◽  
Humic Acid ◽  
Ionic Strength ◽  
Contact Time ◽  
Surface Complexation ◽  
Sorption Isotherms ◽  
Ph Values ◽  
Β Zeolite ◽  
Batch Technique ◽  
Pseudo Second Order

Abstractβ-Zeolite-EDA was modified with ethylenediamine (EDA) after synthesized. The synthesized material was characterized and used for removal of Th(IV) from aqueous solutions. The influences of pH, ionic strength, contact time, temperature and humic acid (HA) on Th(IV) sorption onto synthesized β-zeolite-EDA was studied by batch technique. The dynamic process showed that the sorption of Th(IV) onto β-zeolite-EDA matched the pseudo-second-order kinetics model. The sorption of Th(IV) on β-zeolite-EDA was significantly dependent on pH values, the sorption percentage increased markedly at pH 3.5–4.5, and then maintained a steady state as pH values increased. Through simulating the sorption isotherms by Langmuir, Freundlich and Dubini–Radushkevich (D–R) models, it could be seen respectively that the sorption pattern of Th(IV) on β-zeolite-EDA was mainly controlled by surface complexation, and that the sorption processes was endothermic and spontaneous. The presence of HA increased Th(IV) sorption on β-zeolite-EDA.

Luminescence spectroscopic investigations of europium complexes formed in the kaolinite-humic acid/citric acid systems

2020 ◽  
Vol 108 (11) ◽  
pp. 859-871
Author(s):  
Parveen Kumar Verma ◽  
Prasanta Kumar Mohapatra
Keyword(s):  
Citric Acid ◽  
Humic Acid ◽  
Emission Spectra ◽  
Luminescence Spectroscopy ◽  
Excitation Spectra ◽  
Europium Complexes ◽  
Ternary Complex Formation ◽  
Kaolinite Surface ◽  
Aqueous Complexation ◽  
The Eu

AbstractIn the present study, the nature of Eu(III) complexes (Eu(III) was used as a surrogate for Am(III)) formed in kaolinite–humic acid (HA)/citric acid (CA) system was investigated by luminescence spectroscopy. In addition to the ternary system (kaolinite + Eu + L(CA/HA)), the binary system (Eu-L) was also looked at for a better understanding of the complexes formed at the kaolinite surface. The lifetime and emission spectra of Eu-L complexes on the kaolinite surface differ considerably as compared to the same in the aqueous phase. The Eu-HA aqueous complexation shows differences in the excitation spectra with similar decay lifetimes with increasing aqueous HA concentrations. The ligand-to-metal charger transfer (LMCT) in the Eu-HA excitation spectra suggests the complexation of Eu(III) with HA at pH ∼ 4. Although the mode of Eu(III) binding to the kaolinite surface in the presence of CA/HA was the same i.e. metal-bridged ternary complex formation, the local surroundings around the sorbed Eu(III) differ in the two cases. The loading of HA in the Eu-HA-kaolinite system does not have a large effect on the local structure around the sorbed Eu(III) ion, but enhances the percentage of Eu(III) uptake onto the kaolinite surface. The number of H2O molecules in the primary hydration sphere of sorbed Eu(III) differs in the Eu-HA-kaolinite and Eu-CA-kaolinite systems. In addition, Eu(III) assisted precipitation of HA was also seen using a radiometric method.

Adsorption Mechanism of Humic Acid on Attapulgite Based on Stumm-Schindle Surface Complexation Model

2012 ◽  
Vol 630 ◽  
pp. 99-105 ◽  
Author(s):  
Nan Sun ◽  
Shui Li Yu
Keyword(s):  
Humic Acid ◽  
Ionic Strength ◽  
Zeta Potential ◽  
Adsorption Capacity ◽  
Adsorption Mechanism ◽  
Ph Value ◽  
Surface Complexation ◽  
Practical Significance ◽  
Surface Complexation Model ◽  
Coordination Reaction

Attapulgite from Xuyi in Jiangsu was characterized by X-ray spectrometer and FT-IR spectrophotometer, the coordination reaction degree of attapulgite/water interface and adsorption mechanism of humic acid(HA) on attapulgite was analyzed by Stumm-Schindle(SS) surface complexation model. The results showed that the main component of attapulgite is magnesia-alumina acid salt, the surface charge on attapulgite adapted from hydrolysates of Si-O and Al-O broken bond. After adsorption, zeta potential decreased firstly and then increased with ionic strength increasing, reduced with a pH value increasing. The zero point charge (pHzpc) of attapulgite was about 4~5, zeta potential and adsorption capacity reached the maximum values when pH= 4 and the minimum values when pH=12. The adsorption capacity increased with ionic strength rising. SS surface complexation model could well explain attapulgite / water interfacal coordination reaction, ionic strength can promote the interfacial coordination reaction and reduce electrostatic repulsion effects on adsorption, which has a definite theoretical and practical significance for guiding adsorption experiment and application of attapulgite in water-treatment technology.

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