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The oxidation of sulfur dioxide (SO2) to sulfate in the atmosphere is an important concern in regional air quality, global climate change, and human health. While gas-phase and liquid-phase oxidation of SO2 are widely regarded as important sources of sulfate, the contribution of the heterogeneous oxidation process on particle surfaces is controversial. Recently, this heterogeneous chemistry has been considered to be an important mechanism that is missing in current models to explain sulfate concentrations observed in haze episodes in East Asia. Therefore, the heterogeneous oxidation of SO2 on particles under the conditions of complex air pollution needs to be reassessed. This review summarizes the fundamental understanding of the heterogeneous reactions of SO2 on solid particles such as mineral dust, black carbon, sea salts, organic aerosol, and so on. The factors affecting the mechanism and kinetics of the heterogeneous reactions of SO2, including coexisting components (O3, NO2, H2O2, NH3, and VOCs), reactive sites, surface properties, relative humidity, and illumination, are reviewed. Reactive oxygen species involved in the heterogeneous oxidation of SO2 on particles are discussed. To our knowledge, while previous reviews have appeared on the oxidation of SO2 in the aqueous-phase, this is the first review on the atmospheric heterogeneous reactions of SO2 on the surface of solid particles, which can be of help in understanding the sulfur cycle in the atmosphere and its environmental impacts. A number of recommendations for future research are also presented. [ABSTRACT FROM AUTHOR]

The removal of phenol compounds (such as phenol (Ph), 4-chlorophenol (4-CPh), and 4-phenolsulfonic acid (4-APS)) was studied using catalytic ozonation and cerium oxide (CeO2) as the catalyst. Conventional ozonation removes 40% and 30% of total organic carbon (TOC) for 4-CPh and 4-APS, respectively. The presence of the catalyst doubled the TOC removal in comparison with ozone alone. Chloride and sulfate ions, detached from the target compounds, did not affect the mineralization degree. The effect of ions was studied by adding NaCl and Na2SO4 during the ozonation of Ph with CeO2 as a catalyst. The O3-CeO2 process was responsible for 89% TOC removal, while the presence of NaCl and Na2SO4 decreased TOC removal by nearly 50%. Ozonation alone only removed 20% of TOC at 120 min with or without inorganic salts. The presence of salts in the Ph ozonation provoked in detrimental effect in comparison when inorganic ions were produced along with the decomposition of 4-CPh and 4-APS. [ABSTRACT FROM AUTHOR]

Artificial neural network and response surface methodology have been used to develop a model for simulation and optimization of the removal of Nile blue sulfate by heterogeneous Fenton oxidation. Experimental data were used to train an artificial neural network model with linear transfer function at the output layer and a tangent sigmoid transfer function at the hidden layer. A Box–Behnken design was employed to assess the effects of input process parameters on the total organic carbon removal. First order kinetics and lumped kinetics models were used to describe the reaction; a high regression coefficient indicated that the latter fitted best. The formation of non-oxidizable compounds was shown by liquid chromatography–mass spectrometry. [ABSTRACT FROM AUTHOR]

Methane (CH4) oxidation plays an important role in regulating the atmospheric CH4 balance. Although nitrogen (N) enhancement and sulphate () deposition are major environmental problems facing the Min River estuary in subtropical China, the interactive effects of N and on CH4 oxidation remain poorly understood. We conducted an incubation experiment to investigate the effects of N and additions on CH4 oxidation in marsh soils. CH4 oxidation exhibited distinct seasonal variations, which correlated with changes in temperature and soil moisture; in addition, CH4 oxidation rates were enhanced by the addition of nitrate (), but were slightly inhibited by the addition of ammonium () and . The combined effects of N and on CH4 oxidation were controlled primarily by the form of N, which may imply that inhibition of CH4 oxidation with addition may be counteracted by N addition, especially in estuarine marsh soils with low N and high concentrations. We propose that, although was more effective in stimulating CH4 oxidation and the inhibition caused by and was minor, CH4 oxidation may be inhibited because was dominant and accompanied by strong deposition in the Min River estuary. As such, future CH4 emissions from estuarine wetlands may increase as a result of higher inputs of and . [ABSTRACT FROM AUTHOR]

An efficient and convenient approach for the preparation of functionalized 2-(methylsulfonyl)pyrimidine derivatives has been developed through cyclic condensation of malonate derivatives with S-methylisothiouronium sulfate followed by derivation and oxidation in water-acetone mixture using oxone as the oxidant. This synthetic strategy provides an efficient and environmentally friendly approach for easy access to 2-(methylsulfonyl)pyrimidine derivatives with considerable yields. [ABSTRACT FROM AUTHOR]

The photochemical degradation of two azo and two anthraquinonic dyes was performed using potassium peroxymonosulphate (Oxone®) activated by UV radiation. The fast decolourization of all dyes was observed within 6 min of UV irradiation, with corresponding dye decays higher than 80%. The kinetic rate constants of the dyes' decay were determined, along with the energetic efficiency of the photochemical treatment, taking into account the influence of a few anions commonly present in real wastewaters (i.e., chloride, nitrate, carbonate/bicarbonate and phosphate ions). Chloride and carbonate/bicarbonate ions enhanced dye degradation, whereas phosphate ions exerted an inhibitory effect, and nitrates did not have a predictable influence. The dye decolourization was not associated with efficient mineralization, as suggested by the lack of a significant total organic carbon (TOC) decrease, as well as by the low concentrations of a few detected low molecular weight by-products, including nitrate ions, formaldehyde and organic acids. High molecular weight by-products were also detected by mass spectrometry analysis. The investigated process may be proposed as a convenient pre-treatment to help dye degradation in wastewater during combined treatment methods. [ABSTRACT FROM PUBLISHER]

With the aim of learning about the synergistic effect of a combination of (HOCH2)3P and Na2S2O4 for the bleaching of mechanical pulps, reactions of (HOCH2)3P (and its associated precursor, (HOCH2)4P+Cl−) with Na2S2O4 were studied in aqueous media under Ar and in air. The secondary phosphine (HOCH2)2PH is the major product in a 1:1 reaction of (HOCH2)3P and Na2S2O4 under Ar, the formaldehyde being removed in the form of HOCH2SO3Na and HOCH2SO2Na; the latter is Rongalite, itself an industrial bleaching agent. Significant amounts of the primary phosphine HOCH2PH2 are also seen. When the reaction is performed in air, the oxide (HOCH2)2P(O)H is the main product. Reaction of (HOCH2)4P+Cl− with Na2S2O4 (even under Ar) leads to solely the oxidation products: (HOCH2)3PO, (HOCH2)3PS, and (HOCH2)2P(O)OH. 31P{1H} and 1H NMR spectral data for secondary and primary (hydroxymethyl)phosphines and their oxidation products are reported for the first time. The toxicity of the primary and secondary phosphines is likely to curtail their use in commercial bleaching processes. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT [ABSTRACT FROM AUTHOR]

Poly(o-toluidine) (POT), a derivative of polyaniline, has been synthesized by chemical oxidative polymerization. The synthesized POT is doped with ferrous sulfate. The dc conductivity of POT samples in pellet form is measured in the temperature range of 30°-100°C and is found to increase with temperature, showing the semiconductor nature of the samples. The samples are characterized by UV-visible and FT-IR spectroscopy, and X-ray diffraction pattern. UV-visible studies reveal that direct optical transitions exist in the samples. The X-ray diffraction pattern of powder POT shows semicrystalline nature. FT-IR studies provide information on structural changes in the backbone of POT with chemical doping. [ABSTRACT FROM AUTHOR]

Batch experiments with the lead sulphide ore mineral galena were carried out in order to get information about the oxidation mechanisms and to contribute to the understanding of field data, especially those obtained from the mining-affected sites. Results indicate that oxygen and sulphur isotopes of dissolved sulphate may be useful tools for the investigation of galena oxidation mechanisms. However, some methodological modifications are necessary to obtain sufficient sulphate yields, which are a prerequisite for the reduction of the analytical uncertainty. Surface and hydrochemical investigations indicated that galena was dissolved non-oxidatively during the experiment at initial pH 2, whereas the oxidative dissolution of galena dominated in experiments at initial pH 6 and 8. No isotope results could be obtained from the experiment at initial pH 2 due to the low sulphate production. The oxidative dissolution of galena resulted in somewhat higher sulphate yields. Thus, the oxygen isotope composition of sulphate produced from galena oxidation could be determined for the first time. Oxygen in sulphate derived largely from water molecules; but minor amounts of molecular oxygen could be also observed. Both molecular oxygen and ferric iron may act as oxidants of galena. A variety of intermediate reactions allow for a variable oxygen isotope composition of sulphate. Sulphur isotopes of sulphate showed an enrichment of 32S in sulphate (relative to galena), which increases with increasing pH. Sulphur isotope enrichment processes may be associated with the formation of anglesite. [ABSTRACT FROM AUTHOR]

Oxidation experiments with different pyrite grain sizes (63-100, 100-140, 140-180 μm) were carried out to investigate the oxygen and sulphur isotope composition of sulphate produced under aerobic acid conditions, which may help to understand oxidation mechanisms and to interpret data from natural sites. Long-term experiments with grain size 63-100 μm showed that constant δ 18OSO4 values were not achieved before 100 days. The final oxygen isotope difference between water and sulphate indicates that a small proportion of molecular oxygen is incorporated into sulphate even in the later course of the oxidation due to sulphite oxidation by molecular oxygen. However, most of the sulphate oxygen derives from water. Similar δ 18OSO4 values from experiments with grain sizes 63-100, 100-140, and 140-180 μ m indicate similar oxidation mechanisms for all three grain sizes. These results differed from previous results of identical experiments with grain size<63 μ m, where higher δ 18OSO4 values were obtained. We propose that the greater proportion of molecular oxygen in sulphate from oxidised fine-grained pyrite is caused by an intensified adsorption of molecular oxygen on sulphur sites of ultrafine pyrite particles. Hence, the formation of sulphate from the (initial) reaction on sulphur sites of pyrite and from sulphite oxidation should be more dominant if ultrafine material is present. The δ 34SSO4 values (2.0-2.7) obtained from experiments with the coarser grain sizes agreed with the δ 34S value of pyrite (2.4), whereas sulphur isotopes of sulphate obtained from previous experiments with fine-grained pyrite showed an initial 32S enrichment compared with pyrite. Due to the lack of δ 34SSO4 values from the beginning of the experiments with coarser grain sizes, it remains speculative that sulphur isotopes indicate at least initial differences in oxidation mechanisms between fine and coarser pyrite grain sizes. [ABSTRACT FROM AUTHOR]

Cetyltrimethylammonium peroxodisulfate (CTA)2S2O8 was quantitatively prepared and used for the oxidation and deprotection of trimethylsilyl ethers to the corresponding carbonyl compounds in acetonitrile. Selective oxidation of allylic or benzylic trimethylsilyl ethers in the presence of saturated alkyl trimethylsilyl ethers were also achieved. This new reagent is more efficient and has several advantages over similar oxidants in terms of the amount of oxidant, short reaction time, simple work up, and high yield. [ABSTRACT FROM AUTHOR]

Deprotection of trimethylsilyl ethers to the parent aldehydes and ketones in high yields has been carried out under mild conditions using N-benzyl N,N-dimethyl anilinium peroxodisulfate. [ABSTRACT FROM AUTHOR]

Pit lakes (abandoned flooded mine pits) represent a potential liability or valuable water resource to mining companies, the environment, and regional communities. However, water quality in the pit lakes can often restrict end uses for the water, particularly if affected by acid mine drainage (AMD). Nevertheless, various and diverse treatment strategies now exist for remediating the water quality of these significant post-mining landscape features. Backfilling of the pit may prevent the formation of a pit lake, or may be important in determining the final pit lake shape and bathymetry. Fast filling or contrived lake stratification may also reduce the extent of pyrite oxidation and hence acidity production. Some "active" remediation technologies such as direct liming of pit water are well-proven and effective, but may be expensive to maintain following mine closure and lease relinquishment. Alternatively, other approaches are using "passive" remediation techniques such as stimulation of primary production and sulfate reduction to improve pit water quality. Although there is much promise, there remains great scope for research and monitoring in this multidisciplinary field, before this science can be relied upon for long-term prediction of water quality pertaining to the liability of current and planned pit lakes. [ABSTRACT FROM AUTHOR]

The importance of crustal fluid chemical composition in driving the marine deep subseafloor biosphere was examined in northeast Pacific ridge-flank sediments. At IODP Site U1301, sulfate from crustal fluids diffuses into overlying sediments, forming a transition zone where sulfate meets in situ-produced methane. Enhanced cell counts and metabolic activity suggest that sulfate stimulates microbial respiration, specifically anaerobic methane oxidation coupled to sulfate reduction. Cell counts and activity are also elevated in basement-near layers. Owing to the worldwide expansion of the crustal aquifer, we postulate that crustal fluids may fuel the marine deep subseafloor biosphere on a global scale. [ABSTRACT FROM AUTHOR]

This article describes the oxidation of benzylic, allylic alcohols and hydroquinones under solvent-free conditions using o-xylylenebis(triphenylphosphonium peroxymonosulfate), which has been prepared by mixing an aqueous solution of o-xylylenebis(triphenylphosphonium bromide) with oxone at room temperature. [ABSTRACT FROM AUTHOR]