Gold speciation in natural waters: I. Solubility and hydrolysis reactions of gold in aqueous solution

1990 ◽  
Vol 54 (1) ◽  
pp. 3-12 ◽  
Author(s):  
Dimitrios Vlassopoulos ◽  
Scott A Wood
Keyword(s):  
Aqueous Solution ◽  
Natural Waters ◽  
Hydrolysis Reactions

scholarly journals Hydroxyl radical reactivity at the air-ice interface

2009 ◽  
Vol 9 (5) ◽  
pp. 20881-20911 ◽  
Author(s):  
T. F. Kahan ◽  
R. Zhao ◽  
D. J. Donaldson
Keyword(s):  
Aqueous Solution ◽  
Hydroxyl Radicals ◽  
Natural Waters ◽  
Heterogeneous Reaction ◽  
Radical Reactivity ◽  
Quasi Liquid Layer ◽  
Polycyclic Aromatic ◽  
Nitrite Nitrate ◽  
Spectroscopic Probe

Abstract. Hydroxyl radicals are important oxidants in the atmosphere and in natural waters. They are also expected to be important in snow and ice, but their reactivity has not been widely studied in frozen aqueous solution. We have developed a spectroscopic probe to monitor the formation and reactions of hydroxyl radicals in situ. Hydroxyl radicals are produced in aqueous solution via the photolysis of nitrite, nitrate, and hydrogen peroxide, and react rapidly with benzene to form phenol. Similar phenol formation rates were observed in aqueous solution and bulk ice. However, no reaction was observed at the air-ice interface, or when bulk ice samples were crushed prior to photolysis to increase their surface area. We also monitored the heterogeneous reaction between benzene present at air-water and air-ice interfaces with gas-phase OH produced from HONO photolysis. Rapid phenol formation was observed on water surfaces, but no reaction was observed at the surface of ice. Under the same conditions, we observed rapid loss of the polycyclic aromatic hydrocarbon (PAH) anthracene at the air-water interface, but no loss was observed at the air-ice interface. Our results suggest that the reactivity of hydroxyl radicals toward aromatic organics is similar in bulk ice samples and in aqueous solution, but is significantly suppressed in the quasi-liquid layer (QLL) that exists at the air-ice interface.

Substitution reactions on arsenic(V). The formation and hydrolysis of pentaamminearsenatocobalt(III) in aqueous solution

1973 ◽  
Vol 26 (9) ◽  
pp. 1877 ◽  
Author(s):  
TA Beech ◽  
NC Lawrence ◽  
SF Lincoln
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Bond Formation ◽  
The Other ◽  
Substitution Reactions ◽  
Rate Law ◽  
Hydrolysis Of ◽  
Hydrolysis Reactions

The formation of Co(NH3)5HAsO4+ and Co(NH3)5H2AsO42+ conforms to the rate law: ����������� rate = [Co(NH3)5H2O3+](k-1[HAsO42-]+k-2[H2AsO4-]) where k-1 = (11�1)x10-2 l. mol-1 s-1 and k-2 = (120�15)x10-4 l. mol-1 s-1 at 295 K and unit ionic strength. The hydrolysis of the arsenato complex conforms to the rate law: ������ rate = [total arsenato complex](Ka2k1+k2[H+]+k3[H+]2)(Ka2+[H+])-1 where k1 = (290�15)x10-7s-1, k2 = (408�20)x 10-6 s-1, k3 = (670�34)x10-3 l. mol-1 s-1, and pKa2 = 3.30�0.05 at 295 K and unit ionic strength. The formation and hydrolysis reactions proceed through bond formation and cleavage between oxygen and arsenic. The mechanisms of the reactions characterized by k1 and k-1 are considered to be associative substitutions on arsenic(v), but the mechanisms of the other reactions are less certain.

Photodegradation of amoxicillin in aqueous solution under simulated irradiation: influencing factors and mechanisms

2013 ◽  
Vol 67 (7) ◽  
pp. 1605-1611 ◽  
Author(s):  
Qian Zhao ◽  
Li Feng ◽  
Xiang Cheng ◽  
Chao Chen ◽  
Liqiu Zhang
Keyword(s):  
Aqueous Solution ◽  
Singlet Oxygen ◽  
Natural Waters ◽  
Pure Water ◽  
Chemical Species ◽  
Xenon Lamp ◽  
First Order ◽  
First Order Kinetics ◽  
Photodegradation Rate ◽  
Pseudo First Order

This paper investigated the effects of selected common chemical species in natural waters (HCO3−, NO3− and humic acids (HA)) on the photodegradation of amoxicillin (AMO) under simulated irradiation using a 300 W xenon lamp. Quenching experiments were carried out to explore the mechanisms of AMO photodegradation. The results indicated that AMO photodegradation followed pseudo-first-order kinetics. Increasing AMO concentration from 100 to 1,000 μg L−1 led to the decrease in the photodegradation rate constant from 0.2411 to 0.1912 min−1. The presence of NO3− and HA obviously inhibited the photodegradation rate of AMO because they can compete for photons with AMO. Bicarbonate, as a hydroxyl radical (·OH) scavenger, also adversely affected AMO photodegradation. Quenching experiments in pure water suggested that AMO could undergo self-sensitized photooxidation via ·OH and singlet oxygen (1O2), accounting for AMO removal of 34.86 and 8.26%, respectively. In HA solutions, the indirect photodegradation of AMO was mostly attributed to the produced ·OH (22.37%), 1O2 (24.12%) and 3HA* (20.80%), whereas the contribution of direct photodegradation was to some extent decreased.

scholarly journals Investigation of sorption of 2,4-dichlorophenol on special hungarian oil shale

2018 ◽  
Vol 12 (1) ◽  
pp. 20-29
Author(s):  
Rauch Renáta ◽  
Rita Földényi
Keyword(s):  
Aqueous Solution ◽  
Adsorption Isotherm ◽  
Organic Contaminants ◽  
Oil Shale ◽  
Natural Waters ◽  
Adsorption Properties ◽  
Environmental Technology ◽  
Equilibrium Data ◽  
Bacterial Decomposition ◽  
Chemical Regeneration

The development of efficient methods for the removal of different type of organic contaminates of natural waters is an ever challenging task in the modern environmental technology. The paper reports the physical characterization and adsorption properties of a Hungarian oil shale. Static equilibrium experiments were carried out to study the adsorption of 2,4-dichlorophenol from aqueous solution. The obtained equilibrium data were satisfactorily fitted by a multistep adsorption isotherm within the concentration range of 0 to 100 mg/l. According to our laboratory scale experiments the studied adsorbent immobilizes the contaminants more efficiently than a number of other adsorbents applied in different remediation technologies. More than 90 % of the added 2,4-dichlorophenol was adsorbed by the studied oil shale. The contaminants are bound strongly by the sorbent therefore they cannot be washed out by the groundwater flow which, in turn, favors to the natural bacterial decomposition process of the polluting compound. This is considered as a significant advantage of the adsorbent because no chemical regeneration of the inexpensive oil shale is required. The reported results indicate that the oil shale can be used efficiently for the treatment of natural waters to remove their organic contaminants.

scholarly journals Solvolysis kinetic study and direct spectrofluorimetric analysis of the fungicide benomyl in natural waters

2014 ◽  
Vol 33 (2) ◽  
pp. 237 ◽  
Author(s):  
Diène Diègane Thiare ◽  
Abdourakhmane Khonté ◽  
Diegane Sarr ◽  
Cheikh Diop ◽  
Mame Diabou Gaye-Seye ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Natural Waters ◽  
Limit Of Detection ◽  
Sodium Dodecyl ◽  
Fluorescence Signal ◽  
Aqueous Solvent ◽  
Spectrofluorimetric Method ◽  
Relative Standard ◽  
Triton X

<p>A direct spectrofluorimetric method for the quantitative analysis of benomyl in natural waters is described. Benomyl is an instable, fluorescent fungicide that mainly decomposes into carbendazim and n-butyl-isocyanate in organic and aqueous solutions. The kinetics of benomyl solvolysis reactions were investigated in organic solvents (methanol and acetonitrile) and in aqueous solvent systems, including β–cyclodextrin (β-CD), sodium dodecyl sulfate (SDS), dodecyltrimethylammonium chloride (DTAC), cetyltrimethylammonium chloride (CTAC), cetyltrimethylammonium hydroxide (CTAOH), Brij-700, Triton X-100 and water, at different pH and/or NaOH concentrations. The benomyl fluorescence signal was found to be quasi-completely stable in 10<sup>-2</sup> M NaOH aqueous solution, various alkaline (10<sup>-2</sup> M NaOH) organized media, β-CD neutral solution and Triton X-100 aqueous solutions of different pH. Based on these results, a direct spectrofluorimetric analytical method was developed for the determination of benomyl in 10<sup>-2</sup> M NaOH aqueous solution and Triton X-100 solutions (pH7 and 10<sup>-2</sup> M NaOH), with wide linear dynamic range (LDR) values of two to three orders of magnitude, very low limit of detection (LOD) and limit of quantification (LOQ) values of, respectively, 0.002-0.5 ng/mL and 0.007-2.0 ng/mL, and small relative standard deviation (RSD) values of 0.2-1.7 %, according to the medium. This direct spectrofluorimetric method was applied to the evaluation of benomyl residues in natural waters, with satisfactory recovery values (87-94%).</p>

Kinetics of the formation and hydrolysis reactions of some thiomolybdate(VI) anions in aqueous solution

1987 ◽  
Vol 130 (1) ◽  
pp. 79-83 ◽  
Author(s):  
Nicholas J. Clarke ◽  
Stuart H. Laurie ◽  
Mike J. Blandamer ◽  
John Burgess ◽  
Andrew Hakin
Keyword(s):  
Aqueous Solution ◽  
Kinetics Of ◽  
Hydrolysis Reactions

Antimony(V) complexing with O-bearing organic ligands in aqueous solution: an X-ray absorption fine structure spectroscopy and potentiometric study

2008 ◽  
Vol 72 (1) ◽  
pp. 205-209 ◽  
Author(s):  
M. Tella ◽  
G. S. Pokrovski
Keyword(s):  
Aqueous Solution ◽  
Organic Matter ◽  
Fine Structure ◽  
Functional Groups ◽  
Natural Waters ◽  
Organic Ligands ◽  
X Ray ◽  
Absorption Fine ◽  
Carboxylic Groups ◽  
X Ray Absorption

AbstractThe stabilityand structure of aqueous complexes formed by pentavalent antimony (SbV) with simple organic ligands (acetic, adipic, oxalic, citric acids, catechol and xylitol) having O-functional groups (carboxyl, alcoholic hydroxyl, aliphatic and aromatic hydroxyl) typical of natural organic matter (NOM), were determined at 25°C from potentiometric and X-ray absorption fine structure spectroscopy (XAFS) measurements. In organic-free aqueous solutions, spectroscopic data are consistent with the dominant formation of SbV hydroxide species, Sb(OH)5 and Sb(OH)6-, at acid and near-neutral to basic pH, respectively. Potentiometric measurements demonstrate negligible complexing with mono-functional organic ligands (acetic) or those having non-adjacent carboxylic groups (adipic). In contrast, in the presence of poly-functional carboxylic, hydroxyl carboxylic acids and aliphatic and phenolic hydroxyl, SbV forms stable 1:1 or 1:3 complexes in coordination 6 with the studied organic ligands, over a wide pH range pertinent to natural waters (3 ≤ pH ≤ 9). The XAFS measurements show that in these species the central SbV atom has an octahedral geometry with 6 oxygen atoms from hydroxyl moieties and adjacent functional groups (O = C—OH and/or C—OH) of the ligand, forming bidendate chelate cycles. Stability constants for SbV-oxalate complexes generated from potentiometric experiments were used to model SbV complexing with di-carboxylic functional groups of natural humic acids. Our predictions show that in an aqueous solution of pH between 1 and 4 containing 1 μg/l of Sb and 5 mg/l of dissolved organic carbon (DOC), up to 15% of total dissolved Sb maybe bound to aqueous organic matter via di-carboxylic groups.

Variscite dissolution rates in aqueous solution: does variscite control the availability of phosphate in acidic natural waters?

2008 ◽  
Vol 72 (1) ◽  
pp. 349-351 ◽  
Author(s):  
T. Roncal-Herrero ◽  
E. H. Oelkers
Keyword(s):  
Aqueous Solution ◽  
Natural Waters ◽  
Free Solution ◽  
Pore Fluids ◽  
Mixed Flow ◽  
Dissolution Rates ◽  
Near Surface ◽  
Flow Through ◽  
Solubility Products ◽  
Time Required

AbstractThe dissolution rates of natural well-crystallized variscite (AlPO4.2H2O) were measured from the evolution of aqueous Al and P concentrations in closed and mixed-flow through reactors at 25°C and from 1.5 to 9 pH. Measured dissolution rates decrease with increasing pH from 5.05x10-16 mol/cm2/s at pH = 1.51 to 4.92x10-17 mol/cm2/s at pH = 5.89 and then increase with increasing pH to 1.64x10-17 mol/cm2/s at pH = 8.99. Estimates of the time required to equilibrate a mildly acidic, initially Al- and P-free solution with variscite based on measured dissolution rates and solubility products suggests it takes no more than several weeks to equilibrate this mineral with soil pore fluids. This result suggests that variscite can buffer aqueous phosphate concentrations in a significant number of near surface environments.

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