Presence Of SO2 Research Articles

Insight into the sulfur resistance of manganese oxide for NH3-SCR: Perspective from the valence state distributions

The multiple valence states distributions (VSDs) endowed the catalyst with excellent low temperature de-NOx activity, while little is known about whether the SO2 resistance can be affected by VSDs modulation. In this context, three model manganese oxide catalysts (MnO2, Mn2O3 and Mn3O4) with different valence state distributions were fabricated and evaluated in the NH3-SCR reaction under the presence of SO2. The results show that the three catalysts exhibited a valance-state-dependent SO2 resistance (Mn3O4 > Mn2O3 > MnO2) under the SCR atmosphere with the presence of 100 ppm SO2 at 100 °C within 7 h. Thermal regeneration analysis revealed the overall deactivation was dominated by the remarkably different reversible activity loss proportions, which were found proportionally correlated to the superficial Mn4+/Mnn+ content of the catalysts. Further characterizations indicated the Mn3O4 catalyst with more basic sites and less bulk-like sulfate formation could be the reason for its more slowly deactivation within the limited test period. However, the overall number of basic sites on MnOx is still critically insufficient for longer SO2 resistance test. This work clarified the deactivations details of MnOx from the perspective of valence state distributions, which can provide references for the design of better low temperature SO2-tolerant de-NOx catalyst.

Formation of organic sulfur compounds through SO<sub>2</sub>-initiated photochemistry of PAHs and dimethylsulfoxide at the air-water interface

Abstract. The presence of organic sulfur compounds (OS) at the water surface acting as organic surfactants, may influence the air-water interaction and contribute to new particle formation in the atmosphere. However, the impact of ubiquitous anthropogenic pollutant emissions, such as SO2 and polycyclic aromatic hydrocarbons (PAHs) on the formation of OS at the air-water interface still remains unknown. Here, we observe large amounts of OS formation in the presence of SO2, upon irradiation of aqueous solutions containing typical PAHs, such as pyrene (PYR), fluoranthene (FLA), and phenanthrene (PHE) as well as dimethylsulfoxide (DMSO). We observe rapid formation of several gaseous OSs from light-induced heterogeneous reactions of SO2 with either DMSO or a mixture of PAHs and DMSO (PAHs/DMSO), and some of these OSs (e.g. methanesulfonic acid) are well established secondary organic aerosol (SOA) precursors. A myriad of OSs and unsaturated compounds are produced and detected in the aqueous phase. The tentative reaction pathways are supported by theoretical calculations of the Gibbs energy of reactions. Our findings provide new insights into potential sources and formation pathways of OSs occurring at the water (sea, lake, river) surface, that should be considered in future model studies for a better representation of the air-water interaction and SOA formation processes.

Removal of mercury from flue gas using coal gasification slag

Coal combustion often produces mercury emissions. Coal gasification fine slag (FS) was used to remove Hg0 from flue gas. To increase the removal efficiency, two ionic liquids (IL-T and IL-B) were immobilized on the surface of FS. The mercury removal performance was evaluated in a fixed-bed reactor in the presence of SO2 + O2. The experimental results showed that the mercury removal efficiency increased when the adsorbents were supported by ionic liquids (FS-T and FS-B). The effect of 0.6% SO2 on the capture of Hg0 was negligible for all three adsorbents. The total mercury removal efficiencies exceeded 90% for FS-T and FS-B in the atmosphere of 0.6% SO2 + 6% O2. When the initial mercury concentration was 60 μg/m3, the effective adsorption time was about 80 min for FS and longer than 120 min for FS-T and FS-B. In the presence of 0.6% SO2 + 6% O2, Hg0 and Hg2+ were detected in exhaust gas using FS and FS-B and in solid phase using the three adsorbents. According to XPS analysis, an oxidation reaction occurred on the surface of FS and FS-T. For FS-B, the Br− anion of IL-B was the active site and oxidized Hg0 to Hg2+ on the surface as well as in the gas phase.

Revealing the promotional effect of Ce doping on the low-temperature activity and SO2 tolerance of Ce/FeVO4 catalysts in NH3-SCR

Elimination of NOx from the non-electric industrial boilers has become priority under the effective implementation of ultra-low emissions. A series of Ce-promoted FeVO4 catalysts with improved acidity and reducibility have been synthesized in this work. Thereinto, 10Ce/FeVO4 exhibited an optimum low-temperature performance with 90% of NOx conversion and 95% of N2 selectivity at 200–300 °C which was kept nearly unchanged with different concentrations of SO2 ranging from 50 ppm to 200 ppm, showing a superior sulfur tolerance. An array of well-designed experiments has demonstrated that Ce mainly existed as CeVO4 under a low doping content (1 wt%) on FeVO4, which could efficiently increase the amount of acid sites. With more cerium (5–12 wt%) loading on FeVO4, the appearance of CeO2 further resulted in a strong interaction between cerium species and ion species, thus significantly improving the low-temperature catalytic activity. Therefore, the optimum coexistence of CeVO4 and CeO2 over 10Ce/FeVO4 modulated its Brønsted acid and enhanced its redox circulation of Fe3+ species. Moreover, the NH3-SCR reaction pathways of 10Ce/FeVO4 were broadened from only Eley-Rideal to both Eley-Rideal and Langmiur-Hinshelwood mechanisms after Ce loading on FeVO4 catalyst. With the presence of SO2, the SO/S-O deriving from the generated Ce2(SO4)3 and NH4HSO4 increased the Brønsted acid sites, inducing a satisfying SO2 tolerance of 10Ce/FeVO4 catalyst, although the Langmiur-Hinshelwood pathway of 10Ce/FeVO4 was immediately cut off due to the competitive adsorption of gaseous SO2 and NOx. This work exemplifies a promising strategy for developing an ideal low-temperature NH3-SCR catalyst with good SO2 resistance.

Sulfate-accelerated photochemical oxidation of arsenopyrite in acidic systems under oxic conditions: Formation and function of schwertmannite

The weathering of arsenopyrite is closely related to the generation of acid mine drainage (AMD) and arsenic (As) pollution. Solar radiation can accelerate arsenopyrite oxidation, but little is known about the further effect of SO42− on the photochemical process. Here, the photooxidation of arsenopyrite was investigated in the presence of SO42− in simulated AMD environments, and the effects of SO42− concentration, pH and dissolved oxygen on arsenopyrite oxidation were studied as well. SO42− could accelerate the photooxidation of arsenopyrite and As(III) through complexation between nascent schwertmannite and As(III). Fe(II) released from arsenopyrite was oxidized to form schwertmannite in the presence of SO42–, and the photooxidation of arsenopyrite occurred through the ligand-to-metal charge-transfer process in schwertmannite–As(III) complex along with the formation of reactive oxygen species in the presence of O2. The photooxidation rate of arsenopyrite first rose and then fell with increasing SO42− concentration. In the pH range of 2.0–4.0, the photooxidation rate of arsenopyrite progressively increased in the presence of SO42−. This study reveals how SO42− promotes the photooxidation of arsenopyrite and As release in the AMD environment, and improves the understanding of the transformation and migration of As in mining areas.

High solubility of gold in H2S-H2O ± NaCl fluids at 100–200 MPa and 600–800 °C: A synthetic fluid inclusion study

Numerous previous experimental and theoretical studies of gold deposits in the Earth’s crust have shown that chloride and hydrosulfide are the most abundant ligands in the relevant hydrothermal fluids. However, most of these studies were performed with solutions under relatively oxidizing conditions in the presence of SO42-, HSO4-, and S3-. Reduced sulfur with a −2 valence (e.g., H2S, HS-, etc.) may play a key role in controlling redox conditions and promoting the migration of gold during the formation of epithermaland porphyry gold-copper deposits. To examine this possibility, we performed experiments in reduced H2S-bearing fluids to constrain the effects of temperature, pressure and NaCl concentration on Au solubility through the synthetic fluid inclusion method. Measured amounts of H2S and aqueous solutions (H2O ± NaCl) were loaded in an Au capsule containing a fractured quartz column, and fluid inclusions were formed through healing of these fractures at specified pressures (100 or 200 MPa) and temperatures (600, 700 or 800 °C) for 20 days. Thin sections with both sides polished were prepared from quenched quartz columns, and conventional microthermometric measurements were performed. Raman spectra were collected from all phases in the fluid inclusions from room temperature to 300 °C to identify sulfur species and potential Au-bearing complexes. In all fluid inclusions, S and H2Sn (n ≥ 1) species were identified, but SO2 and SO42-, HSO4- and S3- ions were not observed. Au concentrations in these fluid inclusions, which were analyzed using LA-ICP-MS with NaCl or RbCl reference standards, ranged from 91 to 3599 ppm; they were greatly affected by pressure and NaCl concentration but not obviously by temperature. H2Sn (n > 1) analogs have chemical properties similar to those of H2S, and their deprotonation products (HSn- and Sn2-) exhibit high affinities for Au in aqueous solution. Therefore, HSn-Au (or AuSn-) and Au-Cl could be the dominant species in H2S-bearing hydrothermal fluids and may play important roles during the dissolution and transport stages of Au in ore formation processes.

Removal of high-concentration 4 - Chlorophenol (4-CP) in wastewater using carbon-based heterogeneous catalytic oxidation: Performance and mechanism

The treatment of large quantities of 4-CP wastewater produced in chemical industries has attracted considerable attention due to its high biotoxicity and refractory nature. The heterogeneous Fenton system initiated by carbon-based iron material (HACO-P) was applied to degrade the high concentration 4-CP (2 g/L) wastewater under ambient condition. HACO-P presented excellent adsorption performance with 173.9 mg/g of adsorption capacity. Compared with other heterogeneous Fenton process, 4-CP (100%) and TOC (43%) were degraded within 120 min under optimal conditions of pH of 3.0, [H2O2]0/[4-CP]0 of 6.5, and 3.0 g/L of HACO-P, which demonstrated that more efficient and economical treatment was achieved. Notably, the system exhibited outstanding performance at high concentrations of SO42− and the presence of SO42− can even promote 4-CP removal. Unlike conventional 4-CP degradation mechanisms relying on qualitative analysis of products, four possible intermediates were successfully quantified and 4-CP degradation and dechlorination pathways were proposed. Meanwhile, the mortality rate and malformation rate of zebrafish hatched with three kinds of 4-CP solution decreased gradually with the 4-CP degradation time of 0min, 15min and 120min, which indicated that the toxicity of the 4-CP solution decreased with the extension of degradation time. The feasibility of the system was verified by its stable operation in consecutive rounds of experiments. Overall, this study conclusively provided strong evidence for the heterogeneous Fenton oxidation of high concentration CP wastewater with minimal consumption of reagents.

UV/alcohol gas-phase oxidation combined with sulfite wet absorption for flue gas denitrification

Developing novel advanced oxidation process (AOP) for flue gas denitrification is one of the hot topics in the field of air pollution control. Peroxides, persulfate and peroxymonosulfate are always used as the radical precursors, however it is seldom reported that alcohol species can be used in AOP process. This study first demonstrates that with the assistance of UV185 light, O2 and alcohol exhibit a great synergism in the NO removal. With the assistance of sulfite solution absorption, isopropanol (CH3CH(CH3)OH) and ethanol (CH3CH2OH) could remove 95.6% and 87.5% of NO, respectively, meanwhile the emitted NO2 concentration was controlled below 8 mg/m3. The apparent rate constant of NO removal by using UV185/CH3CH(CH3)OH-O2 and UV185/CH3CH2OH-O2 were calculated to be 0.07356 and 0.05712 s−1, respectively. But the presence of SO2 and CO2 were unfavorable for the NO removal. The formations of alcoxyl radicals, i.e. CH3CH2O• and CH3CH(CH3)O•, were verified by electron spin resonance tests (ESR). The overall reaction route was depicted via quantum chemistry calculation: alcoxyl radicals cooperate with NO* and O• to initiate two radical chain reaction cycles to realize the NO removal. The proposed new method can give new insights into the radical-induced removal of NO and guide the future design of AOP technology for flue gas denitrification.

Degradation of enrofloxacin in aqueous by DBD plasma and UV: Degradation performance, mechanism and toxicity assessment

Enrofloxacin (ENRO) as a highly toxic antibiotic poses great threats to human health and environmental safety. In this study, a novel technology of coupling dielectric barrier discharge (DBD) and ultraviolet (UV) was investigated to efficiently degrade ENRO in aqueous, and had a higher degradation rate. The ENRO degradation rate achieved approximately 93.9% at 30 min, and approximately 1.20 g kWh−1 of energy yield (G50) was observed for the combined system. The addition of H2O2 and K2S2O4 improved the ENRO degradation due to the generation of ·OH and ·SO42-. In the presence of NO3–, the ENRO degradation played a tendency to promote first and then decrease, and the presence of SO42- resulted in the positive effect, while the negative effect was shown in the presence of Cl- and CO32–. The trapping experiment indicated that ·OH played an important part in the ENRO degradation. The addition of UV into the DBD system decreased H2O2 concentration in deionized water, and increased ·OH concentration. The DFT analysis showed the degradation mechanisms of ENRO at a molecular level. The degradation of ENRO mainly involved the oxidation of the piperazine group, the removal of ethyl acetate and the substitution of the F atom. The toxicity of ENRO and its degradation intermediates was evaluated.

Preparation of TiO2/Metalosilicate composites via acrylamide gel method and investigation of their photocatalytic performance for degradation of Brown NG

In this work, the photocatalytic degradation of a specific dye as Brown NG (BNG) by using TiO2 nanoparticles (as the photocatalysts), supported on ZSM-5 type metalosilicate (aluminosilicate, ferrisilicate, and chromosilicate) was reported. The supported and unsupported TiO2 samples were synthesized using acrylamide gel technique in the presence of various anions (produced by the used acids in precursor synthesis solution) containing Clˉ, CH3COOˉ, ClO4−, SO42− and NO3−. The prepared samples were characterized by employing X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–vis diffuse reflectance spectroscopy analysis. XRD analysis results showed that all the used ZSM-5 type metalosilicates (aluminosilicate, ferisilicate, and chromosilicate) for supporting TiO2 nanoparticles could prevent the anatase to rutile transformation after performing calcination at 450 °C. The photocatalytic activities and photodegradation kinetics of the prepared samples were determined by studying the degradation of Brown NG. Considering neat and supported TiO2 samples, pure titania that was prepared in the presence of Clˉ (TECI) and ferrisilicate supported titania that was prepared in the presence of SO42− (TFSI) exhibit the highest photocatalytic efficiency under UV light illumination.

Sulfur-resistant methane combustion invoked by surface property regulation on palladium-based catalysts

Improving sulfur resistance of palladium-based catalysts is crucial for the sustained and efficient methane combustion. Herein, the surface property of catalysts was rationally tailored to tune the dynamic behavior of sulfur species on active sites and supports, which was qualitatively and quantitatively studied through a combination of in-situ and on-line characterizations. Results reveal that the content of accumulated sulfur species in catalysts increased linearly (0.20–0.59 mmol SO2·g−1) with the rise of the surface basic sites, while it was restrained in catalysts with high surface acidity. The zirconium doped alumina supported palladium catalyst exhibited a moderate surface acidity/basicity, meanwhile it showed an excellent catalytic activity in the presence of SO2 and after regeneration. Its enhanced sulfur resistance derived from the proper interaction between supports and sulfur species, the facile decomposition of zirconium sulfates, the suppressed formation of surface/bulk aluminum sulfates, as well as the effective regeneration of PdO phase. The established quantitative correlation between accumulated sulfur species, surface acidity/basicity and catalytic performance paves the way to develop sulfur-resistant palladium-based catalysts for oxidation reactions.

Formation of sulfur oxide groups by SO2 and their roles in mercury adsorption on carbon-based materials

The presence of SO2 display significant effect on the mercury (Hg) adsorption ability of carbon-based sorbent. Yet the adsorption and oxidation of SO2 on carbon with oxygen group, as well as the roles of different sulfur oxide groups in Hg adsorption have heretofore been unclear. The formation of sulfur oxide groups by SO2 and their effects on Hg adsorption on carbon was detailed examined by the density functional theory. The results show that SO2 can be oxidized into SO3 by oxygen group on carbon surface. Both C-SO2 and C-SO3 can improve Hg adsorption on carbon site, while the promotive effect of C-SO2 is stronger than C-SO3. Electron density difference analyses reveal that sulfur oxide groups enhance the charge transfer ability of surface unsaturated carbon atom, thereby improving Hg adsorption. The experimental results confirm that surface active groups formed by SO2 adsorption is more active for Hg adsorption than the groups generated by SO3.

Hg0 Removal by V2O5 Modified Palygorskite in Simulated Flue Gas at Low Temperature

The V2O5-modified palygorskite (V2O5/PG catalysts) were prepared and used for Hg0 removal in simulated flue gas at low temperature. It was found that the V2O5/PG catalyst had excellent performance for Hg0 removal at 150 °C. O2 exhibited a positive effect on Hg0 removal over V2O5/PG, while SO2 and H2O showed an inhibiting effect. However, Hg0 removal efficiency showed a promotion trend in the presence of H2O, SO2, and O2. The Brunauer–Emmett–Teller (BET) method, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were applied to characterize the physicochemical properties of the V2O5/PG catalyst. Mercury temperature-programmed desorption (Hg-TPD) experiments were also conducted to identify the mercury species adsorbed on the V2O5/PG catalyst, and the pathway of Hg0 removal over V2O5/PG was also discussed. The used V2O5/PG catalyst after Hg0 removal was regenerated, and its capability for Hg0 removal can be completely recovered. The V2O5/PG-Re-300 °C catalyst showed excellent performance and good stability for Hg0 removal after regeneration.

Chemical Bath Deposited Orthorhombic SnS Films for Solar Cell Applications

Tin sulfide (SnS) thin films were deposited by the chemical bath deposition technique. The used procedure allows us to obtain orthorhombic SnS in 3.5 h and achieve thicknesses of 390 nm. We study the influence of deposition times, percentage of Sn precursor, and post-annealing on the structural and optical properties. The X-ray diffraction measurements of SnS films prepared at a deposition time of 3 h showed orthorhombic structure with characteristic peaks of SnS2. However, increasing the deposition time and the Sn precursor, the orthorhombic SnS phase in these samples becomes predominant. Thin-film morphologies and thicknesses were identified by scanning electron microscopy (SEM). An increase in bandgap from 1.41 eV to 1.56 eV was observed by increasing Sn precursor. The optical properties remain constant after air annealing of 285 °C. Low-temperature photoluminescence spectra show emission bands at 2.5 eV attributed to the presence of SO2. Other deep level transitions were observed at about 0.9 eV, probably due to oxygen.

Research progress in the SO<sub>2</sub> resistance of denitration catalysts in low-temperature NH<sub>3</sub>-SCR reactions

<p indent="0mm">NH₃-SCR reaction is one of the most widely used denitration technologies at present, and the catalyst is the core of the NH₃-SCR technology. Because of its low-temperature activity and easy deactivation in the presence of SO₂, the research on the low-temperature sulfur-resistance of denitration catalysts becomes a hot spot. In this review, the deactivation mechanism of NH₃-SCR catalysts in the presence of SO₂ is reviewed. It is found that the deactivation of the catalysts is mainly due to the reaction of SO₂ with NH₃ and metal-active sites; the formation of ammonium sulfates or ammonium bisulfates will block the pores of the catalysts and affect the efficiency of the catalysts; the metal sulfates will lead to the deactivation of the active sites of the catalysts and cause the irreversible deactivation of the catalysts; the competitive adsorption of SO₂ and NO will also cause the deactivation of the catalysts. Based on the known mechanism of catalyst deactivation, some effective strategies for improving the SO₂ tolerance are proposed: reducing the adsorption and oxidation of SO₂, constructing sacrificial sites to protect active sites and promoting the decomposition of sulfates. It is found that the sulfur resistance of the catalysts can be improved by some methods: such as metal modification, the special structure of catalysts, the influence of supports, acid catalysts. Finally, the development prospect of low-temperature sulfur-resistant NH₃-SCR denitration catalysts is prospected.

Interplay between emulsion stability and wettability alteration: An application for water-based enhanced oil recovery methods

Low salinity waterflooding (LSW) is a popular enhanced oil recovery method, which is mainly grounded on rock wettability improvement. Nevertheless, according to recent studies, the application of LSW is accompanied by some practical challenges, such as the formation of unwanted water-in-oil (w/o) emulsions, which emphasizes the necessity for optimization of the injected brine composition. The present study aims to assess the simultaneous role of brine chemistry and its corresponding potential determining ions (PDIs) on rendering rock hydrophobicity and the formation of tight w/o emulsions. To this end, seawater (SW) and its dilutions combined with a number of ion-engineered solutions consisting of PDIs, namely Mg2+, Ca2+, and SO42- were used to perform a set of contact angle and emulsion stability experiments. The design of experiment (DoE) methodology was also used to optimize the brine chemistry for low salinity water injection based on the outcomes of the experiments. We found that lowering ionic strength of brine from 0.8 mol.L-1 down to 0.1 mol.L-1 provides favorable conditions to generate stable w/o emulsions, with a separated water volume (SWV) as low as 5% of the total initial water after one day of aging at 80 °C. Also, as to the dynamic contact angle results, reduction of brine’s ionic strength down to 0.1 mol.L-1 without ion-tunning improved the wettability alteration index (WAI) merely about 0.2. However, for the ion-tuned solutions, the presence of Mg2+ cations was found not to be in favor of the low salinity effect. Since not only does it cause a small change in the wetting state (WAI < 0.5), but it also boosts the emulsion’s longevity, markedly (SWV < 15%). Contrarily, the presence of SO42- in the brine solution appeared to be more promising because of its strong potential for rendering surface wettability and also reducing emulsion longevity (SWV greater than 50%). As to the presence of Ca2+ cations, results indicated more water-wet surfaces with the WAI of 0.8. Nonetheless, based on the SWV results, Ca2+ cations are prone to form stable emulsions, with SWV ranging from 30% to 5% of the total initial water. Finally, based on the optimization results from DoE, a brine composition in which the concentration of divalent cations (i.e. Mg2+ and Ca2+) is kept minimal and SO42- is the dominant divalent ions is highly likely to induce a unit desirability condition. Also, it was found that the presence of Mg2+ and SO42- in the aqueous phase significantly affects wettability alteration and emulsion generation processes. According to the findings of this study, both brine salinity and its ionic composition should be carefully formulated as they can direct the low salinity effect either in positive or negative ways by improving wettability or generating stable emulsions. The outcomes of the present study can serve as a method for optimizing the water-based enhanced oil recovery approaches.

Covellite nanoparticles with high photocatalytic activity bioproduced by using H2S generated from a sulfidogenic bioreactor

The application of sulfate reducing bacteria (SRB) has emerged as an efficient biotechnology to reduce sulfate to sulfide and to mediate the precipitation of transition metals as sulfides. In the present work, hydrogen sulfide biogenerated by the SRB was delivered into a copper aqueous solution vessel to produce copper sulfide nanoparticles. The main physico-chemical properties were studied by TEM, XRD, UV–vis spectroscopy, fluorescence spectroscopy, UPS and XPS. In addition, the photocatalytic activities for organic dyes removal were investigated, showing a high degradation rate of MB and RD in aqueous solution. By changing the copper concentration during the synthesis process, main physico-chemical properties of copper sulfides nanoparticles can be controlled. For the lowest concentration, pure covellite flake-like nanostructures were produced. Higher concentrations produced spherical-like shapes with the presence of SO42− on the surface. Experimental results showed a promising way to obtain valorous copper sulfides nanoparticles by using dissimilatory reduction of sulfate mediated by SRB.

SO2-enhanced nitrate photolysis on TiO2 minerals: A vital role of photochemically reactive holes

In this study, we investigated the nitrate photolysis on photoactive TiO2 particles in the presence of SO2 through theoretic DFT calculation and in situ DRIFTS analysis, and found that in a clean atmosphere nitrate was oxidized to •NO3 radicals by the holes generated on the surface of TiO2 under solar irradiation, followed reactive nitrogen species generation via •NO3 radicals reduction by photoinduced electrons. After shifting to the SO2-polluted environment, •NO3 radicals preferentially reacted with abundant sulfites to significantly increase nitrogen species formation, the online measured concentrations of NOx and HONO increased by approximately 2-fold and 6-fold respectively in comparison with clean atmosphere. These results demonstrate that photogenerated holes play a key role in nitrate photolysis on photoactive mineral dusts with or without the coexistence of SO2, providing new insights into the source of NOx and HONO in complex air polluted areas during the daytime.

A facile synthesis of quinoxalines by using SO4 2−/ZrO2-TiO2 as an efficient and recyclable heterogeneous catalyst

Quinoxaline derivatives have been synthesized in good to excellent yields by the cyclocondensation reaction of o-pheneylenediamine with substituted phenacyl bromides/benzil in the presence of SO4 2−/ZrO2-TiO2 as an efficient and heterogeneous catalyst. The catalyst can be recovered up to five catalytic cycles without significant loss in catalytic activity. The reported SO4 2−/ZrO2-TiO2 catalyst has been thoroughly characterized by using infrared spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and powder X-ray diffraction (XRD). Here, we have used ethanol as a green solvent in this cyclocondensation. This new method has several advantages, such as excellent yields, short reaction time, nontoxic, and easily recoverable catalyst.

Degradation mechanism and eco-toxicity assessment of bisphenol S based on peroxymonosulfate activated with Co3O4 surfaces

In this paper, the degradation mechanism and eco-toxicity assessment of bisphenol S (BPS) was studied in the aqueous environment based on the heterogeneous activation of peroxymonosulfate (PMS) through spinel tricobalt tetraoxide (Co3O4) catalyst using density functional theory (DFT) and computational toxicology methods. The result indicates that (100) and (311) surfaces have the higher proportion of bivalent cobalt, the increase of charge transfer, negative adsorption energy, and the lower surface energy. They can more effectively promote the decomposition of PMS to generate reactive oxide species. When generated oxidants react with BPS, HO•-addition reaction at the ortho-C atom-sites plays a dominant role in the system Co3O4/PMS. The presence of SO4•-, HO•, and O2 promotes the formation of transformation intermediates and products. The formation pathways of important experimental intermediates hydroquinone, p-hydroxybenzenesulfonic acid, and 3, 4-dihydroxybenzenesulfonic acid are identified. And, some hydroxylation products that are not identified in the experiment are determined. The eco-toxicity evaluation shows that most of the decomposition products are completely harmless or significantly reduced compared to BPS. This study not only provides insights into the degradation mechanism of BPS in Co3O4/PMS system, but also is expected to be a guide for further experimental research and the design and optimization of the activated catalysts in sulfate radical-based advanced oxidation technologies.