scholarly journals EPR study of the production of oh radicals in aqueous solutions of uranium irradiated by ultraviolet light

2009 ◽  
Vol 74 (6) ◽  
pp. 651-661 ◽  
Author(s):  
Marko Dakovic ◽  
Milos Mojovic ◽  
Goran Bacic
Keyword(s):  
Aqueous Solutions ◽  
Hydroxyl Radicals ◽  
Fluorescence Decay ◽  
Uranyl Acetate ◽  
Oh Radicals ◽  
Solution Ph ◽  
Trapping Method ◽  
Wide Ph Range ◽  
Ph Range ◽  
Epr Spin Trapping

The aim of the study was to establish whether hydroxyl radicals (?OH) were produced in UV-irradiated aqueous solutions of uranyl salts. The production of ?OH was studied in uranyl acetate and nitrate solutions by an EPR spin trap method over a wide pH range, with variation of the uranium concentrations. The production of ?OH in uranyl solutions irradiated with UV was unequivocally demonstrated for the first time using the EPR spin-trapping method. The production of ?OH can be connected to speciation of uranium species in aqueous solutions, showing a complex dependence on the solution pH. When compared with the results of radiative de-excitation of excited uranyl (+22*UO ) by the quenching of its fluorescence, the present results indicate that the generation of hydroxyl radicals plays a major role in the fluorescence decay of + 22 *UO . The role of the presence of carbonates and counter ions pertinent to environmental conditions in biological systems on the production of hydroxyl radicals was also assessed in an attempt to reveal the mechanism of +22*UO de-excitation. Various mechanisms, including ?OH production, are inferred but the main point is that the generation of ?OH in uranium containing solutions must be considered when assessing uranium toxicity.

Utilization of cross-linked chitosan/bentonite composite in the removal of methyl orange from aqueous solution

2014 ◽  
Vol 71 (2) ◽  
pp. 174-182 ◽  
Author(s):  
Ruihua Huang ◽  
Qian Liu ◽  
Lujie Zhang ◽  
Bingchao Yang
Keyword(s):  
Methyl Orange ◽  
Aqueous Solutions ◽  
Ph Value ◽  
Maximum Adsorption Capacity ◽  
Order Kinetic ◽  
Wide Ph Range ◽  
Order Kinetic Model ◽  
Langmuir Isotherm Model ◽  
Ph Range ◽  
A Minor

A kind of biocomposite was prepared by the intercalation of chitosan in bentonite and the cross-linking reaction of chitosan with glutaraldehyde, which was referred to as cross-linked chitosan/bentonite (CCS/BT) composite. Adsorptive removal of methyl orange (MO) from aqueous solutions was investigated by batch method. The adsorption of MO onto CCS/BT composite was affected by the ratio of chitosan to BT and contact time. pH value had only a minor impact on MO adsorption in a wide pH range. Adsorption kinetics was mainly controlled by the pseudo-second-order kinetic model. The adsorption of MO onto CCS/BT composite followed the Langmuir isotherm model, and the maximum adsorption capacity of CCS/BT composite calculated by the Langmuir model was 224.8 mg/g. Experimental results indicated that this adsorbent had a potential for the removal of MO from aqueous solutions.

At the crossroad of photochemistry and radiation chemistry: formation of hydroxyl radicals in diluted aqueous solutions exposed to ultraviolet radiation

2017 ◽  
Vol 19 (43) ◽  
pp. 29402-29408 ◽  
Author(s):  
Kateřina Tomanová ◽  
Martin Precek ◽  
Viliam Múčka ◽  
Luděk Vyšín ◽  
Libor Juha ◽  
...  
Keyword(s):  
Ultraviolet Radiation ◽  
Aqueous Solutions ◽  
Hydroxyl Radicals ◽  
Radiation Chemistry ◽  
Quantum Yields ◽  
Oh Radicals

We provide evidence on the formation of ˙OH radicals via 253.7 nm photolysis of aqueous solutions, determine their quantum yields, and apply the knowledge to photo-induced formation of phospholipid hydroperoxides.

Amidoxime-functionalized hydrothermal carbon materials for uranium removal from aqueous solution

RSC Advances ◽  
2016 ◽  
Vol 6 (104) ◽  
pp. 102462-102471 ◽  
Author(s):  
Zhibin Zhang ◽  
Zhimin Dong ◽  
Ying Dai ◽  
Saijin Xiao ◽  
Xiaohong Cao ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
High Selectivity ◽  
Carbon Materials ◽  
Uranium Removal ◽  
Wide Ph Range ◽  
Ph Range

Amidoxime-functionalized hydrothermal carbon (AO-HTC) has been synthesized and applied to adsorb U(vi) from aqueous solutions, exhibiting a high selectivity above 60% for a wide pH range from 1.0 to 5.0.

Effect of ammonium, carbonate and fluoride concentration on the uranium recovery by resins

2005 ◽  
Vol 93 (4) ◽  
Author(s):  
Ana C. Q. Ladeira ◽  
Carlos A. Morais
Keyword(s):  
Exchange Process ◽  
Fluoride Concentration ◽  
Alkaline Solutions ◽  
High Concentration ◽  
Solution Ph ◽  
Uranium Recovery ◽  
Strong Base ◽  
Base Resin ◽  
Wide Ph Range ◽  
Ph Range

SummaryUranium in solution can be precipitated over a wide pH range, from acidity and alkalinity, depending upon the solution and the precipitant used. The precipitate is generally filtered and the solution resultant contains uranium that should be recovered. This work is aimed at the selection of an appropriate resin for uranium recovery from alkaline solutions in the presence of ammonia, carbonate and fluoride. The ability of uranium extraction of 3 types of polymeric strong base resin was assessed. Laboratory solutions were prepared to determine the influence of the ions like ammonia, carbonate and fluoride on the uranium recovery by resins. The uranium concentration was 100 mg/L and the solution pH ranged from 9.2 to 10.4. The results, obtained by batch experiments, showed that excess of carbonate and fluoride completely inhibit uranium uptake in the pH range studied. Even low concentrations of fluoride and carbonate decrease uranium adsorption by resins. The optimum concentration was below 2.5 g/L (0.04 mol/L) and 5.0 g/L (0.26 mol/L) for carbonate and fluoride, respectively. The presence of high concentration of ammonia up to 20 g/L (1.20 mol/L) did not inhibit the uranium exchange process. Among the three types of resins studied IRA 910U was the most promising adsorbent for uranium at the conditions employed in this work.

scholarly journals Photolysis of sulfosalicylic acid in aqueous solutions over a wide pH range

2006 ◽  
Vol 181 (1) ◽  
pp. 37-43 ◽  
Author(s):  
Ivan P. Pozdnyakov ◽  
Victor F. Plyusnin ◽  
Vjacheslav P. Grivin ◽  
Dmitry Yu. Vorobyev ◽  
Nikolai M. Bazhin ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Sulfosalicylic Acid ◽  
Wide Ph Range ◽  
Ph Range

scholarly journals Enhanced fluoride removal from drinking water in wide pH range using La/Fe/Al oxides loaded rice straw biochar

2021 ◽  
Author(s):  
Nan Zhou ◽  
Xiangxin Guo ◽  
Changqing Ye ◽  
Ling Yan ◽  
Weishi Gu ◽  
...  
Keyword(s):  
Drinking Water ◽  
Rice Straw ◽  
Fluoride Concentration ◽  
Fluoride Removal ◽  
Batch Adsorption ◽  
Solution Ph ◽  
Adsorption Sites ◽  
Wide Ph Range ◽  
Rice Straw Biochar ◽  
Ph Range

Abstract A novel and highly efficient adsorbent was prepared by loading La/Fe/Al oxides onto rice straw biochar (RSBC) and was tested for the ability to remove fluoride from drinking water. Characterized by SEM, XRD, Zetapotential and FTIR, it was found that the ternary metal oxides were successfully loaded on the surface of biochar in amorphous form, resulting in the formation of hydroxyl active adsorption sites and positive charges, which played a synergistic role in fluoride removal. Through batch adsorption tests, key factors including contact time, initial fluoride concentration, initial pH and co-existing anions effects were investigated. Results showed that the tri-metallic modified biochar (La/Fe/Al-RSBC) had excellent fluoride removal performance with an adsorption capacity of 111.11 mg/g. Solution pH had little impacts on the removal of fluoride, the adsorbent retained excellent fluoride removal capacity in a wide pH range of 3.0–11.0. The co-existing anions had almost no effect on the fluoride removal by La/Fe/Al-RSBC. In addition, La/Fe/Al-RSBC could be regenerated and reused. Electrostatic adsorption and ion exchange were responsible for this adsorption behavior. These findings suggested the broad application prospect of a prepared biochar adsorbent based on rare earth and aluminum impregnation for the fluoride removal from drinking water.

scholarly journals Radionuclide 106Ru behavior in aqueous solutions by ion exchange, ultrafiltration, and centrifugation methods

2021 ◽  
Vol 57 (3) ◽  
pp. 331-339
Author(s):  
O. B. Korenkova ◽  
A. V. Radkevich ◽  
N. I. Voronik
Keyword(s):  
Ion Exchange ◽  
Aqueous Solutions ◽  
Waste Treatment ◽  
Membrane Separation ◽  
Liquid Radioactive Waste ◽  
Ionic Species ◽  
Species Formation ◽  
Wide Ph Range ◽  
Ph Range ◽  
Ru Species

The paper presents the results of 106Ru radionuclide behavior regularities study in aqueous solutions in a wide pH range by ultrafiltration, ion exchange and centrifugation methods. The regions of 106Ru various species existence in solution have been established: cationic 106Ru species at pH < 3.5; the transition region of non-ionic species formation in the range of pH 3.5–4.2 and the region of non-ionic species predominant formation at pH > 4.2. A characteristic feature of the studied solutions is the formation of non-ionic particles by microconcentrations of 106Ru via pseudocolloids at lower pH values as compared to ruthenium solutions with a concentration of 10-6–10-4 mol/dm3. The established regularities of the behavior of ruthenium radionuclides can be utilized to increase the efficiency of ion exchange and membrane separation methods at nuclear and radiation facilities for technological solutions and liquid radioactive waste treatment.

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