Presence Of SO2 Research Articles

Shell-core MnO2/Carbon@Carbon nanotubes synthesized by a facile one-pot method for peroxymonosulfate oxidation of tetracycline

• MnO 2 /C@CNT for PMS activation was fabricated via a facile one-pot method. • Increased Mn (III)/Mn (IV) and surface –OH are the basis for high catalytic activity. • SO 4 · - and · OH play dominant roles in TC degradation in the MnO 2 /C@CNT-PMS system. • The toxicity of solution finally decreased after the MnO 2 /C@CNT-PMS process. In this study, a new type of MnO 2 /carbon@carbon nanotubes (MnO 2 /C@CNT) shell-core nanohybrid for peroxymonosulfate (PMS) activation was synthesized by a one-pot method, which simultaneously achieved the synthesis of MnO 2 and assembly of components. Tetracycline (TC) degradation by MnO 2 /C@CNT-PMS was enhanced obviously, and MnO 2 /C@CNT (1.75:1)-PMS systems exhibited the best TC degradation efficiency (85.6%) at 10 min. In addition, the effects of catalyst dosage, PMS dosage, initial pH, reaction temperature, and co-existing ions on the degradation of TC were investigated. The stripping and insertion of the nanocarbon during the synthetic process were the basis for the enhancement of the Mn (III)/Mn (IV) ratio and surface –OH groups, which further accelerated electron transfer and the conversion of Mn and O species. EPR analysis along with the free-radical quenching experiments confirmed the presence of SO 4 · - and · OH during the catalytic reaction, among which SO 4 · - was the main active specie. Moreover, a comprehensive toxicity assay and prediction were performed based on bioluminescence inhibition experiments and the Ecological Structure Activity Relationships (ECOSAR) program. Finally, reasonable degradation pathways of TC were proposed based on LC-MS analysis.

Co-Deposition Mechanisms of Calcium Sulfate and Calcium Carbonate Scale in Produced Water

Co-precipitation of mineral-based salts during scaling remains poorly understood and thermodynamically undefined within the water industry. This study focuses on investigating calcium carbonate and calcium sulfate mixed precipitation in scaling. Scaling is often observed in the produced water supply as a result of treatment processes. Co-precipitation results were compared with experimental results of a single salt crystallization. Several parameters were carefully monitored, including the electrical conductivity, pH value, crystal morphology and crystal form. The existence of the calcium carbonate scale in the mixed system encourages the loose calcium sulfate scale to become more tightly packed. The mixed scale was firmly adhered to the beaker, and the adhesion of the co-deposition product was located between the pure calcium sulfate scale and the pure calcium carbonate scale. The crystalline form of calcium sulfate was gypsum in both pure material deposition and mixed deposition, while the calcium carbonate scale was stable in calcite form in the pure material deposition. In the co-deposition, apart from calcite form, some calcium carbonate scale crystals had metastable vaterite form. This indicated that the presence of SO42− ions reduced the energy barrier of the calcium carbonate scale and hindered its transformation from a vaterite form to a calcite one, and the increase in HCO3− content inhibited the formation of calcium sulfate scale.

Removal of Sb(V) from wastewater via siliceous ferrihydrite: Interactions among ferrihydrite, coprecipitated Si, and adsorbed Sb(V)

Although ferrihydrite (Fh) exhibits good Sb(V) adsorption behavior, the instability of its amorphous structure limits its engineering applications. In this study, siliceous ferrihydrite (SiFh) was prepared via coprecipitation to resolve these limitations. X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and SiFh aging tests revealed that the growth of Fh particles covered with Fe–O–Si links was inhibited while maintaining their amorphous structure. Meanwhile, the XRD patterns indicated that SiFh maintained excellent stability after five adsorption–desorption cycles. During the aging process, the added Si decreased the electrostatic interaction between SiFh and Sb(V), which weakened the affinity between Sb(V) and Fh; however, most of the Sb(V) still entered the Fe lattice after seven days of aging, which was favorable for Sb(V) recovery during reutilization. Furthermore, Sb(V) adsorbed from the simulated textile wastewater onto SiFh had the highest adsorption energy (Eads), which meant its unstable inner-sphere complexation on the surface of SiFh. Meanwhile, the presence of SO42−, NO3−, Ca2+, and Mg2+ contributed to Sb(V) outer-sphere adsorption. Both of these factors were conducive to Sb(V) desorption. Hence, SiFh is a promising adsorbent owing to its facile preparation process, stability, and optimal regeneration properties.

Degradation of a non-oxidizing biocide in circulating cooling water using UV/persulfate: Kinetics, pathways, and cytotoxicity

In industry, isothiazolinone (a mixture containing 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT) and 2-methyl-4-isothiazolin-3-one (MIT), CMIT-MIT) as a non-oxidizing biocide is extensively used to control the growth of microorganisms in the circulating cooling water system, which potentially threatens the ecological environment and human health. In this work, the oxidative degradation of CMIT-MIT by UV/persulfate (PS) technology on a laboratory-scale was systematically investigated. The degradation of CMIT-MIT was greatly improved by UV/PS compared with only UV or oxidant. During the photolysis of 60 mg/L PS, the degradation rate and TOC mineralization rate of CMIT-MIT were 91% and 34.7%, respectively. The contributions of .OH and SO4·− to CMIT-MIT degradation in the UV/PS system were estimated to be 0.93% and 32.12% respectively. The degradation rate of CMIT-MIT decreased slightly with the increase of pH. The presence of SO42− and NO3− had no significant effect on the degradation of CMIT-MIT, while the presence of Cl− and CO32− inhibited the CMIT-MIT removal rate. The degradation pathways and three possible intermediates of CMIT-MIT were obtained. After degradation of CMIT-MIT by UV/PS process, the cytotoxicity decreased within 20 min, effectively indicating that UV/PS could be as a potential technology to remove the CMIT-MIT in water treatment.

Oxidation-absorption process for simultaneous removal of NOx and SO2 over Fe/Al2O3@SiO2 using vaporized H2O2

3% Fe/Al2O3 and 3% Fe/Al2O3@SiO2 were prepared to investigate the performance in simultaneous removal of NOx and SO2 using vaporized H2O2. Certain paraments were changed to explore the activity of catalysts, including temperature, H2O2 concentration, GHSV and coexistence gases component. A 24-h durability test was conducted on 3% Fe/Al2O3@SiO2. Moreover, a series of characterizations were employed to analyze the physical and chemical properties of catalysts, including XRD, BET, SEM, TEM, FTIR and XPS. Compared with 3% Fe/Al2O3, 3% Fe/Al2O3@SiO2 exhibited more excellent catalytic activity, which could achieve the peak removal efficiency of 100% for SO2 and 93.76% for NOx. Moreover, 3% Fe/Al2O3@SiO2 kept stable simultaneous removal efficiency in a 24-h test. The characterization results indicated that the BET area was greatly improved and the core-shell structure was synthesized with the formation of more micropores and mesopores by the coating of SiO2, which could improve the activity of catalyst at high temperature and high SO2 concentration. Besides, the mechanism of SO2 molecules on simultaneous removal was investigated. On one hand, a part of H2O2 was consumed by SO2 molecules without catalyst, which resulted in the drop of NOx removal by the decrease of oxidants. The main products were sulfites and bisulfites, which were broken down into SO2 over the catalyst. On the other hand, the presence of SO2 was beneficial for NOx removal by increasing oxygen vacancies on the catalyst surface and facilitating the absorption of NO2 by NaOH solution.

An environmental and highly active Ce/Fe-Zr-SO42- catalyst for selective catalytic reduction of NO with NH3: The improving effects of CeO2 and SO42-

A series of Ce/Fe-Zr-SO42- catalysts have been prepared and developed for selective catalytic reduction of NO with ammonia (NH3-SCR). The catalysts were characterized by XRD, H2-TPR, N2 adsorption-desorption, NH3-TPD and DRIFTS. The characterization results demonstrated that the coexistence of cerium and sulfuric acid on Fe-Zr catalyst could contribute to excellent SCR performance. Among all samples, Ce/Fe-Zr-0.3 S catalyst showed the optimal NOX conversion, reaching more than 80% at 250 °C at a GHSV of 60,000 h−1. Moreover, the optimum concentration of SO42- to modify Ce/Fe-Zr catalyst was 0.3 mol/L. The low sulfuric acid concentration contributed to improving low-temperature activity, while high concentration leaded to outstanding high-temperature activity. According to H2-TPR and NH3-TPD, the presence of SO42- increased the total amount of acid sites and more stable sulfate species were formed with higher concentration of sulfuric acid. In situ DRIFTS revealed the NH3 molecule was mainly activated at the Lewis acid site and reacted with the adsorbed NOX species (such as bidentate nitrates) to produce N2 and H2O, which conformed to the L-H reaction mechanism.

Involvement of Ethylene in Reversal of Salt Stress by Salicylic Acid in the Presence of Sulfur in Mustard (Brassica juncea L.)

The involvement of ethylene in reversal of salt (NaCl; 50 mM) stress on photosynthetic activity and growth by salicylic acid (SA; 0.5 mM) together with sulfur (S; 2.0 mM) was studied in mustard (Brassica juncea L. cv. Pusa Vijay). Application of SA plus SO42− improved photosynthetic activity through markedly increased S-assimilation, strengthening antioxidant defense system and limiting NaCl-accrued oxidative consequences more conspicuously than their individual effect in B. juncea under 50 mM NaCl stress. Since SA acts as an inhibitor of ethylene and S-assimilation is associated with ethylene synthesis, we tried to figure out the interaction of ethylene in SA and SO42−-mediated salt tolerance. The involvement of ethylene was studied by supplementing salt-treated plants with 200 µL L−1 ethephon (an ethylene-releasing compound) or 100 µM norbornadiene (NBD, ethylene action inhibitor) to SA and SO42− treatments. Ethephon supplemented to NaCl-treated plants showed optimal ethylene formation, increasing ethylene sensitivity to enhance photosynthesis by affecting antioxidative capacity of plants. SA plus SO42− treatment decreased stress ethylene production and optimized ethylene formation under NaCl stress that contributed in the maintenance of high photosynthetic rate, which was reversed with NBD. NaCl-treated plants receiving SA plus SO42− and supplemented with NBD showed inhibited photosynthetic characteristics and growth, with minimal S-assimilation capacity, activity of antioxidant enzymes and GSH content. This showed that the reversal of salt stress by SA plus SO42− was through ethylene involvement. Overall, ethylene intervened the effect of SA in the presence of SO42− to induce S-assimilation, upregulated the enzymatic and non-enzymatic antioxidants, and imparted NaCl tolerance in plants.

Reaction chemistry of PbSO4 formation over Al2O3 sorbent

Al2O3 has been considered as an effective sorbent of lead removal from the SO2-containing flue gas. The reaction chemistry between PbCl2 and SO2 over Al2O3 surface was systemically explored by quantum chemistry calculations. The results suggest that the chemisorption mechanism is responsible for PbCl2 and SO2 adsorption over Al2O3 surface. The intense orbital hybridization and overlap are related to strong chemisorption of PbCl2 and SO2 over Al2O3 surface. PbSO4 can be produced from the reaction between PbCl2 and SO3 generated from SO2/SO3 transformation. SO2/SO3 transformation includes three steps: SO2 → SO2(ads) → SO3(ads) → SO3. The reaction pathway between PbCl2 and SO3 over Al2O3 surface contains six steps: O2 adsorption, SO3(ads) → SO4(ads), PbCl2 → PbCl2(ads), PbCl2(ads) → PbSO4(ads), PbSO4 desorption, and Cl2 desorption. The rate-determining step (RDS) of PbSO4 formation over Al2O3 surface is SO2 oxidation due to its larger energy barrier. The activation energy barriers of SO2 oxidation over Al2O3 (001) and Al2O3 (110) surfaces are 114.56 and 416.03 kJ/mol, respectively. Al2O3 (001) surface exhibits higher activity for PbSO4 formation than Al2O3 (110) surface. This study of reaction mechanism can be conducive to better comprehend the transformation of lead species on Al2O3 sorbent in the presence of SO2.

Fe3＋ coordinated to amino-functionalized spherical mesoporous silica: Preparation, characterization, and application as a rapid and efficient adsorbent for As(V) removal

A facile hydrothermal synthetic method was employed for the preparation of Fe 3＋ coordinated to amino-functionalized spherical mesoporous silica (Fe–NH 2 –SMS), aimed at the rapid and efficient removal of As(V) from water. The morphology, structure and properties of the adsorbent were characterized via SEM, EDS, N 2 adsorption–desorption, FT-IR, zeta-potential and XPS. Fe–NH 2 –SMS exhibited a high performance for As(V) removal with a very fast adsorption rate (reaching equilibrium within 1 min). As(V) adsorption on Fe–NH 2 –SMS was better fitted to the Langmuir isotherm model ( R 2 = 0 .988). The maximum adsorption capacity was 43.34 mg g –1 As(V) at 25 °C. The optimum pH for As(V) adsorption was in the range of 5–10. The individual presence of SO 4 2– , SO 3 2– , HPO 4 2– and CO 3 2– had a negative effect on As(V) adsorption. The removal of As(V) via Fe–NH 2 –SMS in real water samples remained above 95% with an increasing adsorbent dosage up to 1.6 g L –1 . Reusability studies indicated that the removal of As(V) was still up to 76% after five adsorption–desorption cycles. Electrostatic attraction and inner-sphere complexation between As(V) and functional groups (–NH 2 ⋅ ⋅ ⋅ Fe 3＋ ) were identified as the adsorption mechanisms of As(V). The prepared adsorbent can be considered a promising adsorbent for the rapid adsorption of As(V) from water. • Fe–NH 2 –SMS can reach the adsorption equilibrium within 1 min of contact time. • Fe–NH 2 –SMS showed wide pH applicability (5–10). • Fe–NH 2 –SMS exhibited the excellent As(V) removal of 99%. • As(V) removal of real water samples was satisfactory. • As(V) adsorption mechanism was electrostatic attraction and inner-sphere complexation.

Kosmotropic and chaotropic behavior of hydrated ions in aqueous solutions in terms of expansibility and compressibility parameters

Hydrated ions have fundamental applications in chemical and biological processes. Kosmotropic and chaotropic nature of hydrated ions affect the water structure in solutions depending upon their hydrophobicity or hydrophilicity nature. In present study Kosmotropic and chaotropic behavior of hydrated ions have been explained in terms of volumetric and acoustic parameters like apparent molar volume ( V ϕ ), expansibility and compressibility factors for aqueous electrolytic solutions provide useful information about interactions among ions and water molecules. Results of V ϕ showed that SO 4 2− ions due to stronger H-bonding with water molecules are termed as kosmotropes while Cl − and HCO 3 – are chaotropes due to their weaker H-bonding with water molecules. More compressible structure of solutions in the presence of SO 4 2− ions indicated its kosmotropic behavior and comparatively less compressible structure of solutions in the presence of Cl −1 and HCO 3 – ions renders them chaotropes. Results obtained from expansibility factor showed the dominance of electrostatic interactions over hydrophobic hydration of ions at higher temperatures. Greater values of expansibility factor for SO 4 2− ions as compared to Cl −1 and HCO 3 – ions renders them kosmotropic ion while later are termed as chaotropes. Hence, thermo-acoustic parameters could be effectively used to describe the hydrogen bonding character of ionic solutions in terms of kosmotropic and chaotropic behavior of solutions.

An investigation on the promoting effect of Pr modification on SO2 resistance over MnOx catalysts for selective reduction of NO with NH3.

Pr-modified MnOx catalyst was synthesized through a facile co-precipitation process, and the results showed that MnPrOx catalyst exhibited much better selective catalytic reduction (SCR) activity and SO2 resistance performance than pristine MnOx catalyst. The addition of Pr in MnOx catalyst led to a complete NO conversion efficiency in 120-220°C. Moreover, Pr-modified MnOx catalyst exhibited a superior resistance to H2O and SO2 compared with MnOx catalyst. After exposing to SO2 and H2O for 4h, the NO conversion efficiency of MnPrOx catalyst could remain to 87.6%. The characterization techniques of XRD, BET, hydrogen-temperature programmed reduction (H2-TPR), ammonia-temperatureprogrammed desorption (NH3-TPD), XPS, TG and in situ diffuse reflectance infrared spectroscopy (DRIFTS) were adopted to further explore the promoting effect of Pr doping in MnOx catalyst on SO2 resistance performance. The results showed that MnPrOx catalyst had larger specific surface area, stronger reducibility, and more L acid sites compared with MnOx catalyst. The relative percentage of Mn4+/Mnn+ on the MnPrOx-S catalyst surface was also much higher than those of MnOx catalyst. Importantly, when SO2 exists in feed gas, PrOx species in MnPrOx catalyst would preferentially react with SO2, thus protecting the Mn active sites. In addition, the introduction of Pr might promote the reaction between SO2 and NH3 rather than between SO2 and Mn active sites, which was also conductive to protect the Mn active sites to a great extent. Since the presence of SO2 in feed gas had little effect on NH3 adsorption on the MnPrOx catalyst surface, and the inhibiting effect of SO2 on NO adsorption was alleviated, SCR reactions could still proceed in a near-normal way through the Eley-Rideal (E-R) mechanism on Pr-modified MnOx catalyst, while SCR reactions through the Langmuir-Hinshelwood (L-H) mechanism were suppressed slightly.

Investigation of Mn doped perovskite La-Mn oxides for NH3-SCR activity and SO2/H2O resistance

A series of Mn doped perovskite La-Mn oxides were prepared and characterized systematically·NH3-SCR activity and the resistance to SO2 and/or H2O were evaluated. The results showed that LM-1.4 catalyst displays excellent LT SCR activity and wide window (80% NOx conversion in 100–300 °C). In the presence of SO2 and H2O, LM-1.4 catalyst can also achieve about 95% NOx conversion and N2 selectivity in long-term testing and good SCR activity (above 80% NOx conversion in 145–300 °C) in the cycles. The Mn doped La-Mn oxides have SBET of 86 m2/g and Vtotal of 0.27 cm3/g, but some Mn oxides do not enter the perovskite framework and form Mn3O4 and MnO2. Mn substituted A-site La ions in perovskite La-Mn oxides changes some of Mn3+ at the B-site in LaMnO3 to Mn4+ and some at the A-site to Mn2+. Doping of Mn can change redox properties of perovskite La-Mn oxides, but after the resistance testing in the presence of SO2 and H2O, the decrease of Mn4+ content and active oxygen species on the catalyst surface can weaken the redox properties of La-Mn oxides. Mn doping increases significantly the adsorption amount of NH3, but the formation of sulfate increases the strong acidity of the catalyst. Mn doping can also accelerate the decomposition of ammonium sulfate, resulting in an improvement of SO2-resistance.

Characteristics and Mechanisms of Bacteriophage MS2 Inactivation in Water by UV Activated Sodium Persulfate

Viruses in the aquatic environment have strong resistance to common disinfection techniques. To contribute to the development of efficient virus inactivation technologies, the characteristics and mechanisms of virus inactivation in a UV activated sodium persulfate(UV/PS) system were studied. The inactivation rate and kinetic characteristics of bacteriophage MS2 in water samples by the UV/PS were studied. The effects of PS dosage, pH, and the initial concentration of bacteriophages on the inactivation effect were also investigated. Furthermore, the morphologies of phages before and after UV/PS treatment were observed by transmission scanning electron microscope, and the free radicals in the reaction system were identified by electron paramagnetic resonance spectroscopy. By means of a free radical quenching experiment, the contribution rate of various factors in the UV/PS system to phage inactivation was also analyzed and calculated. The results showed that when the UV irradiation intensity was 160 μW·cm-2, the phage MS2 of 4.39 lg could be removed after UV/PS treatment for 4 min, which was 1.44 lg higher than that of the same UV dose alone. The inactivation of phage MS2 by the UV/PS system was in accordance with the first-order kinetic model. Increasing the initial concentration of PS in the system significantly improved the inactivation rate of phages, while pH and the initial concentration of phages had little effect on the inactivation rate. UV/PS treatment damages the capsid of phages and promotes the aggregation of phage particles. The presence of SO4-· and·OH in the UV/PS system was an important factor for the inactivation of MS2 phages. Finally, ·OH contributed more to MS2 phage inactivation than SO4-·.

Influence of carbonate minerals on the pyrolysis and phase behavior of oil

The concept that reservoir minerals can affect oil cracking behavior is widely accepted by geochemists. However, the role of carbonate minerals on the thermal evolution of oil is still not well understood. This is especially true for dolomite, which is one of the most important carbonate cements. To investigate its influence, a series of laboratory simulation experiments of a crude oil with various carbonate minerals, including calcite, magnesite, and dolomite was conducted. The simulation experiments were carried out using a closed system of flexible gold capsules at temperatures of 250–600°С at a heating rate of 20 °C/h and a constant pressure of 50 MPa. The results indicate that dolomite/magnesite might promote the generation of sulfate radical ion (SO42−). Subsequently, the presence of SO42− can initiate thermochemical sulfate reduction reaction with the help of minor water and H2S, resulting in the destruction of gaseous hydrocarbons. Meanwhile, the influence of dolomite on the composition of oil can further affect its phase behavior, especially in the gas window (Easy Ro range of 1.19–1.47% in the experiments). For the investigated oil, at Easy Ro of 1.47%, the presence of dolomite will increase the cricondentherm (ca. 35 °C) and decrease the cricondenbar (ca. 1.3 MPa) compared to those of pure oil.

Analysis of Transcriptomic Response to SO2 by Oenococcus oeni Growing in Continuous Culture.

ABSTRACTTo successfully complete malolactic fermentation (MLF), Oenococcus oeni must overcome wine stress conditions of low pH, high ethanol, and the presence of SO2. Failure to complete MLF may result in detrimental effects to the quality and stability of the resulting wines. Research efforts to date have focused on elucidating the mechanisms and genetic features that confer the ability to withstand low pH and high ethanol concentrations on O. oeni; however, the responses to SO2 stress are less well defined. This study focused on characterizing the transcriptional response of O. oeni to SO2 challenge during cultivation in a continuous system at wine-like pH (3.5). This experimental design allowed the precise discrimination of transcriptional changes linked to SO2 stress from responses associated with growth stage and cultivation parameters. Differential gene expression analysis revealed major transcriptional changes following SO2 exposure and suggested that this compound primarily interacts with intracellular proteins, DNA, and the cell envelope of O. oeni. The molecular chaperone hsp20, which has a demonstrated function in the heat, ethanol, and acid stress response, was highly upregulated, confirming its additional role in the response of this species to SO2 stress. This work also reports the first nanopore-based complete genome assemblies for O. oeni.IMPORTANCE Malolactic fermentation is an indispensable step in the elaboration of most wines and is generally performed by Oenococcus oeni, a Gram-positive heterofermentative lactic acid bacterium species. While O. oeni is tolerant to many of the wine stresses, including low pH and high ethanol concentrations, it has high sensitivity to SO2, an antiseptic and antioxidant compound regularly used in winemaking. Understanding the physiological changes induced in O. oeni by SO2 stress is essential for the development of more robust starter cultures and methods for their use. This study describes the main transcriptional changes induced by SO2 stress in the wine bacterium O. oeni and provides foundational understanding on how this compound interacts with the cellular components and the induced protective mechanisms of this species.

Effects of sulfation on the ash fusibility and minerals evolution of corn straw during oxy-fuel combustion

Oxy-biomass combustion is an important technology for achieving negative CO2 emission. However, during oxy-biomass combustion, a series of ash-related problems are induced because of the accumulation of recycled SO2. In this study, the effects of SO2 on the ash fusibility were systematically investigated through ash fusion temperatures (AFTs) tests, scanning electron microscopy (SEM), inductively coupled plasma atomic emission spectrometer (ICP-OES), X-ray diffraction (XRD), and chemical thermodynamics calculation (FactSage). Besides, the relevance among minerals evolution, melting performance, and ash sulfation was established. It was found that the presence of SO2 suppressed the release of K and Ca species, thereby increasing the AFTs of corn straw, while this depended heavily on the SO2 concentration, the duration of ash sulfation, and the initial concentration of O2. Furthermore, two reacting mechanisms, including moderate and excessive sulfation, were proposed in this work. When the initial SO2 concentration was less than 1000 ppm, AFTs increased due to the transformation of alkaline chlorides to their sulfates and aluminosilicates with the presence of SiO2 and Al2O3 in ash samples, which was named as moderate sulfation. When the concentration of SO2 was higher than 1000 ppm, large amounts of KAlSi3O8, CaAl2Si2O8, Ca2Al2SiO7 and CaSO4 were generated, causing the simultaneous eutectic and CaO-assisted melting, thereby decreasing the AFTs of corn straw, which was named as excessive sulfation.

Effect of oxidants and dopant on morphology, crystallinity and optical absorbance of nano structural polyindole

We prepared the nanostructural polyindoles S1, S2, S3 and S4 (Pinds) by chemical oxidative route using anhydrous Iron (III) chloride (ferric chloride - FeCl3) and (NH4)2S2O8 (ammonium persulfate - APS) as oxidants and H2O2 (Hydrogen peroxide) as a dopant. The Pind samples are characterized by FTIR, UV–vis and XRD spectroscopy. The morphology of said samples has been examined by electron microscopy, SEM and TEM. The FTIR spectrographs enriched with bands show various bond absorptions which give the identity of Pind. The UV–vis spectra of S1 shows the absorption peaks in both regions, UV and visible. Using an oxidant as APS, the sample S2 spectra show the absence of an absorption peak in the visible region. The use of APS as oxidant gives the bathochromic and hyperchromic shift for UV absorption peak in case of S2 compare to S1, and also on the spectra of S2 there is bathochromic and hyperchromic shift in IR region which may be effect of APS as oxidant while polymerization. Hypsochromic shift is observed for samples S3 and S4, at both π - π* band and n- π* band with the use of dopants while synthesizing. Decrease in particle size (<100 nm) of S2 compared with S1 examined by SEM images (surface morphology). Small sized particles are observed in sample S3 compared to sample S1 with the use of H2O2 as dopant. The SEM image of S4 shows the presence of aggregation of particles up to some extent so that sheet- like structure is observed. Presence of Cl- in polymer matrix ensured by 4.64 wt% Cl on EDAX of S1, presence of SO2 - or SO3 - or SO4 - in polymer matrix ensured by 13.1 wt% oxygen and 2.89 wt% sulphur on EDAX of S2. Presence of Cl- in the polymer matrix is confirmed by EDAX of S3 and presence of SO2 - or SO3 - or SO4 - in the polymer matrix is confirmed by EDAX of S4. Increase in crystalline nature, formation of nano crystallites and removal of nanowires structure revealed by the XRD pattern of S2 due to APS as an oxidant. Nanoparticles surrounded by polymer nanowires are shown by the TEM image of S1. Nano crystallites embed spherical particles (>100 nm) as shown by the TEM image of S2. Small sized particles are observed in sample S3 (Pind/FeCl3/H2O2) compared to sample S1. In the present study we tried to find how the nature of oxidant affects the morphology, crystallinity and optical absorbance of Pind.

Effect of exposure time with SO2 as an impurity on the corrosion behaviour of pipeline steel in CCS transportation

ABSTRACT This study was aimed at evaluating the effects of exposure time and SO2 as one of the impurities on the corrosion behavior of steel pipeline transporting supercritical CO2 during carbon capture and storage. Steel coupons were exposed to supercritical CO2 with various concentrations of SO2 for durations up to 1512 hours. Weight loss measurements were performed to evaluate the steel corrosion behavior. The weight loss results revealed a decrease in corrosion rate with an increase in exposure time which was mainly attributed to the gradual increase of the mineral layer on the steel surface. The increase in SO2 concentration within supercritical CO2 increased the corrosion rate from 0.0109 mm/yr to the highest value of 1.396 mm/yr. X-ray diffraction analysis revealed that the mineral layer formed on the steel surface under pure supercritical CO2 mainly consisted of siderite while iron sulfite hydrate was observed under in the presence of SO2.

Synergistically boosting sulfamerazine degradation via activation of peroxydisulfate by photocatalysis of Bi2O3-TiO2/PAC under visible light irradiation

Photocatalysis-activated sulfate-radical advanced oxidation process (SR-AOP) is an effective approach to remove organic micropollutants from water. Here, we tested a photocatalysis-activated SR-AOP in which peroxydisulfate (PDS) was activated by composites of Bi2O3-TiO2 photocatalyst supported onto commercial powdered activated carbon (Bi2O3-TiO2/PAC) under visible light irradiation. This “Vis-Cata-PDS” treatment exhibited outstanding degradation performance (97.96% removal) towards sulfamerazine (SMZ) following optimized reaction conditions of 0.1 g/L Bi2O3-TiO2/PAC and 0.1 g/L PDS at pH of 7. Synergistic effects were observed between the visible-light photocatalytic activation of PDS via direct electron transfer and nonradical PDS activation over pristine PAC within Bi2O3-TiO2/PAC. Both active radicals (SO4·−, h+, ·O2−) and nonradical singlet oxygen (1O2) and the mediated electron transfer of pristine PAC within Bi2O3-TiO2/PAC were contributed to SMZ degradation. Based on intermediates identified by Liquid Chromatograph-Mass Spectrometer (LC-MS) combined with density functional theory (DFT) calculations, three degradation pathways were proposed and that were mostly attributed to SO2 extrusion/Smiles-type rearrangement and S-N bond cleavage, and toxicity of intermediates were effectively alleviated. An inhibitory effect on SMZ degradation was observed for presence of HCO3−, whereas presence of SO42− was less inhibitory and Cl− had no effect. The Bi2O3-TiO2/PAC composite displayed excellent reusability and stability, and it was effective towards a number of tested micropollutants (sulfadiazine, sulfamethoxazole, ciprofloxacin, bisphenol A and methyl orange) and in real water matrixes. This work offers deep insights into the nonradical oxidation mechanism and application of Vis-Cata-PDS over a Bi2O3-TiO2/PAC composite for removal of organic micropollutants.

Contribution of Urban Forests to the Ecosystem Service of Air Quality in the City of Santo Domingo, Dominican Republic

A survey on pollutants that affect air quality was carried out at 27 points in the city of Santo Domingo, National District. The removal of air pollutants was estimated in relation to the city’s forest cover; using the iTree Canopy software. A principal components analysis and a correlation analysis was also performed to identify the association of these variables. The results show that the average percentage of green infrastructure in the sampling points was 26%. Also, positive correlation was identified between the presence of NO2 and SO2 at the sampling points. It was observed that the higher the presence of forest cover, the higher the concentration of CO and the lower the presence of pollutants. Although five hot spots were defined in terms of air pollution levels in the National District, the study does not show conclusive results regarding the relationship between green infrastructure and air quality in Santo Domingo. Results show that urban planning for environmental quality requires inter-institutional coordination, permanent ecological quality monitoring, and coordinated public policies to establish adequate indicators comparable to the World Health Organization standards.