A critical review towards the causes of the iron-based catalysts deactivation mechanisms in the selective oxidation of hydrogen sulfide to elemental sulfur from biogas

Hydrogen sulfide(H_(2)S) not only presents significant environmental concerns but also induces severe corrosion in industrial equipment,even at low concentrations.Among various technologies,the selective oxidation of hydrogen sulfide(SOH_(2)S) to elemental sulfur(S) has emerged as a sustainable and environmentally friendly solution.Due to its unique properties,iron oxide has been extensively investigated as a catalyst for SOH_(2)S;however,rapid deactivation has remained a significant drawback.The causes of iron oxide-based catalysts deactivation mechanisms in SOH_(2)S,including sulfur or sulfate deposition,the transformation of iron species,sintering and excessive oxygen vacancy formation,and active site loss,are thoroughly examined in this review.By focusing on the deactivation mechanisms,this review aims to provide valuable insights into enhancing the stability and efficiency of iron-based catalysts for SOH_(2)S.

Effect of grinding with sulfur on surface properties and floatability of three nonferrous metal oxides

Co-grinding three nonferrous metal oxides(CuO,PbO and ZnO)with element sulphur under mild conditions and flotation of the ground samples were conducted to investigate the surface properties and floatability of the oxides.Phase transition,morphological features,electrochemical properties and surface chemical compositions of ground samples were studied.The results show that the floatability of CuO is improved after grinding with sulfur,by the formation of surface layer with properties similar to CuS due to the Cu-S bonding.The floatability of PbO is deteriorated after mechanochemical processing due to surface carbonation and the formation of PbS and PbSO4by disproportionation reaction with sulfur.ZnO shows no evident response to mechanochemical sulfidation.

Simultaneous Determination of Halogen Compounds and Sulfur Oxides in Flue Gas by Ion Chromatography

Ion chromatography （IC） is a suitable analytical method for the determination of anions. As analytical methods for the halogen compounds in flue gas, those of bromine compound, fluorine compound, chlorine （Cl2） and hydrogen chloride （HCI） are listed in JIS. However, IC has not been adopted in JIS except for HCI and C12. Because the carbon dioxide in flue gas is absorbed in a 0.1 M sodium hydroxide solution as an absorber, it is interfered with the measurement of F^- and Cl^- ions. This paper describes the development of the pretreatment equipment for the flue gas analysis by IC, and its applications to real flue gas analysis. The F^-, Cl^-, Br^- and SO4^2- in the absorbing solution can be clearly separated by IC using the pretreatment equipment. The halogen compounds and sulfur oxides in flue gas can be simultaneously determined by IC.

The effect of glutathione on glucosinolate biosynthesis through the sulfur assimilation pathway in pakchoi associated with the growth conditions

Glucosinolates(GSLs) are a group of nitrogen-and sulfur-containing secondary metabolites, synthesized primarily in members of the Brassicaceae family, that play an important role in food flavor, plant antimicrobial activity, resistance to insect attack, stress tolerance, and human anti-cancer effects. As a sulfur-containing compound, glutathione has a strong connection with GSLs biosynthesis as a sulfur donor or redox system, and exists in reduced(glutathione;GSH) and oxidized(glutathione disulfide;GSSG) forms. However, the mechanism of GSH regulating GSLs biosynthesis remainds unclear. Hence, the exogenous therapy to pakchoi under normal growth condition and sulfur deficiency condition were conducted in this work to explore the relevant mechanism. The results showed that exogenous application of buthionine sulfoximine, an inhibitor of GSH synthesis, decreased the transcript levels of GSLs synthesis-related genes and transcription factors, as well as sulfur assimilation-related genes under the normal growth condition. Application of exogenous GSH inhibited the expression of GSLs synthesis-and sulfur assimilation-related genes under the normal condition, while the GSLs biosynthesis and the sulfur assimilation pathway were activated by exogenous application of GSH when the content of GSH in vivo of plants decreased owing to sulfur deficiency. Moreover,exogenous application of GSSG increased the transcript levels of GSLs synthesis-and sulfur assimilation-related genes under the normal growth condition and under sulfur deficiency. The present work provides new insights into the molecular mechanisms of GSLs biosynthesis underlying glutathione regulation.

Antagonism effect of residual S triggers the dual-path mechanism for water oxidation

Transition metal chalcogenides(TMCs)are recognized as pre-catalysts,and their(oxy)hydroxides derived from electrochemical reconstruction are the active species in the water oxidation.However,understanding the role of the residual chalcogen in the reconstructed layer is lacking in detail,and the corresponding catalytic mechanism remains controversial.Here,taking Cu_(1-x)Co_(x)S as a platform,we explore the regulating effect and existence form of the residual S doped into the reconstructive layer for oxygen evolution reaction(OER),where a dual-path OER mechanism is proposed.First-principles calculations and operando~(18)O isotopic labeling experiments jointly reveal that the residual S in the reconstructive layer of Cu_(1-x)Co_(x)S can wisely balance the adsorbate evolution mechanism(AEM)and lattice oxygen oxidation mechanism(LOM)by activating lattice oxygen and optimizing the adsorption/desorption behaviors at metal active sites,rather than change the reaction mechanism from AEM to LOM.Following such a dual-path OER mechanism,Cu_(0.4)Co_(0.6)S-derived Cu_(0.4)Co_(0.6)OSH not only overcomes the restriction of linear scaling relationship in AEM,but also avoids the structural collapse caused by lattice oxygen migration in LOM,so as to greatly reduce the OER potential and improved stability.

Efficient aerobic oxidative desulfurization via three-dimensional ordered macroporous tungsten-titanium oxides

A series of three-dimensional ordered macroporous(3 DOM)W-TiO_(2)catalysts have been prepared through a facile colloidal crystal template method.The prepared materials characterized in detail exhibited enhanced catalytic activity in aerobic oxidative desulfurization process.The experimental results indicated that the as-prepared materials possessed excellent 3 DOM structure,which is beneficial for the catalytic activity.The sample 3 DOM W-TiO_(2)-20 exhibited the highest activity in ODS process,and the sulfur removal can reach 98%in 6 h.Furthermore,the oxidative product was also analyzed in the reaction process.

Characterization of apparent sulfur oxidation activity of thermophilic archaea in bioleaching of chalcopyrite

The apparent sulfur oxidation activities of four pure thermophilic archaea, Acidianus brierleyi （JCM 8954）, Metallosphaera sedula （YN 23）, Acidianus manzaensis （YN 25） and Sulfolobus metallicus （YN 24） and their mixture in bioleaching chalcopyrite were compared, which were characterized indirectly by the evolution of the cells concentration, pH value and sulfate ions concentration in solution. The results show that the mixed culture contributed significantly to the raising of leaching rate, which suggests that the mixed culture had a higher sulfur oxidation activity than the pure culture. Meanwhile, the results also indicate that the changes of parameters characterizing the sulfur oxidation activity of thermophilic archaea are often influenced by many factors, so it is hard to reflect accurately the specific sulfur oxidation activities among the different sulfur-oxidizing microbes when bioleaching chalcopyrite at different conditions. Accordingly, an efficient method to characterize microbial sulfur oxidation activity appears to be desirable.

Catalytic reduction of SO_2 by CO over CeO_2-TiO_2 mixed oxides

The structure and catalytic desulfurization characteristics of CeO2-TiO2 mixed oxides were investigated by means ofX-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and catalytic activity tests. According to the results, a CeO2-TiO2solid solution is formed when the mole ratio of cerium to titanium n（Ce）：n（Ti） is 5：5 or greater, and the most suitable n（Ce）：n（Ti） isdetermined as 7：3, over which the conversion rate of SO2 and the yield of sulfur at 500℃ reach 93% and 99%, respectively.According to the activity testing curve, Ce0.7Ti0.3O2 （n（Ce）：n（Ti）=7：3） without any pretreatment can be gradually activated by reagentgas after about 10 min, and reaches a steady activation status 60 min later. The XPS results of Ce0.7Ti0.3O2 after different time ofSO2＋CO reaction show that CeO2 is the active component that offers the redox couple Ce4＋/Ce3＋ and the labile oxygen vacancies, andTiO2 only functions as a catalyst structure stabilizer during the catalytic reaction process. After 48 h of catalytic reaction at 500℃,Ce0.7Ti0.3O2 still maintains a stable structure without being vulcanized, demonstrating its good anti-sulfur poisoning performance.

Differential utilization of cyclic, orthorhombic α- and chain-like polymeric μ-sulfur by Acidithiobacillus ferrooxidans

The differential utilization of cyclic, orthorhombic α-sulfur （α-S） and chain-like polymeric g-sulfur （μ-S） by Acidithiobacillus ferrooxidans was investigated. The growth and sulfur oxidation results indicated that utilization of μ-S by A. ferrooxidans was clearly different from α-S. Even if the planktonic cells were produced, the fall of pH and the rise of sulfate concentration were the same after 300 h on each substrate, the speeds of the planktonic cells increase, pH decrease and sulfate concentration increase in the earlier cultivation stage were faster on polymeric sulfur compared with the orthorhombic form. The adsorption capacity of the cells was higher on μ-S than on α-S, The results of SEM, DRIFTS and XRD analyses indicated that the surfaces of α-S and μ -S were modified differently by cells. Differential expression of 11 selected sulfur adsorption-activation and metabolism relevant genes was detected by RT-qPCR. The results showed that the expression of the hydrophobic substrate transport proteins and the sulfur metabolism related proteins was up-regulated, and the adsorption and activation related proteins were down-regulated when the cells were grown on μS, suggesting that μ-S could be more easily bio-adapted and activated than α-S.

In situ sulfur-doped mesoporous tungsten oxides for gas sensing toward benzene series

Benzene series as highly toxic gases have inevitably entered human life and produce great threat to human health and ecological environment,and thus it is distinctly meaningful to monitor benzene series with quickly,real-time and efficient technique.Herein,novel sulfur-doped mesoporous WO_(3)materials were synthesized via classical in-situ solvent evaporation induced co-assembly strategy combined with doping engineering,which possessed highly crystallized frameworks,high specific surface area(40.9–63.8 m^(2)/g)and uniform pore size(~18 nm).Benefitting from abundant oxygen vacancy and defects via S-doping,the tailored mesoporous S/m WO_(3)exhibited excellent benzene sensing performance,including high sensitivity(50 ppm vs.48),low detection limit(ca.500 ppb),outstanding selectivity and favorable stability.In addition,the reduction of band gap resulted from S-doping promotes the carrier migration in the sensing materials and the reaction at the gas–solid sensing interfaces.It provides brand-new approach to design sensitive materials with multiple reaction sites.

Study on Catalytic Wet Oxidation of H_2S into Sulfur on Fe/Cu Catalyst

A wet catalytic oxidation at room temperature was investigated with solution containing ferric, ferrous and cupric ions for H2S removal. The experiments were carried out in a two step process, and the results obtained show that the removal efficiency of H2S can always reach 100% in a 300 mm scrubbing column with four sieve plates, and the regeneration of ferric ions in 200 mm bubble column can match the consumed ferric species in absorption. Removal of H2S, production of elemental sulfur and regeneration of ferric, cupric ions can all be accomplished at the same time. No raw material is consumed except O2 in flue gas or air, the process has no secondary pollution and no problem of catalyst degradation and congestion.

The Oxidation State of Sulfur Detected in Na_2O-CaO-SiO_2 Float Glass by X-ray Absorption Near Edge Structure Spectra

The oxidation state of sulfur is detected in Na20-CaO-SiO2 float glass by synchrotron radiation X-ray absorption near edge structure （XANES） spectra at the sulfur K edge. The measured spectra show the only presence of S^6＋ in the Na20-CaO-SiO2 float glass and the oxidation state of sulfur do not change with the increase of glass depth. It is also found that, after the melt has gone through the molten tin bath, the S^6＋ is the dominant species, but S^2- is also present on both surfaces. It is not certain whether cation bonds to S^2- or not, because there are many cations dissolved in the melted tin which makes the spectrum complicated.

Isolation and characterization of ferrous-and sulfur-oxidizing bacteria from Tengchong solfataric region,China

Microbial oxidation and reduction of iron and sulfur are important parts of biogeochemical cycles in acidic environments such as geothermal solfataric regions. Species of Acidithiobacillus and Leptospirillum are the common ferrous-iron and sulfur oxidizers from such environments. This study focused on the Tengchong sofataric region, located in Yunnan Province, Southwest China. Based on cultivation, 9 strains that grow on ferrous-iron and sulfuric compounds were obtained. Analysis of 16S rRNA genes of the 9 strains indicated that they were affiliated to AcidithiobaciUus, Alicyclobacillus, Sulfobacillus, Leptospirillum and Acidiphilium. Physiological and phylogenetic studies indicated that two strains （TC-34 and TC-71） might represent two novel members of Alicyclobacillus. Strain TC-34 and TC-71 showed 94.8%-97.1% 16S rRNA gene identities to other species of Alicyclobacillus. Different from the previously described Alicyclobacillus species, strains TC-34 and TC-71 were mesophilic and their cellular fatty acids do not contain w-cyclic fatty acids. Strain TC-71 was obligately dependent on ferrous-iron for growth. It was concluded that the ferrous-iron oxidizers were diversified and Alicyclobacillus species were proposed to take part in biochemical geocycling of iron in the Tengchong solfataric region.

Formation and Oxidation of Hydrogen Molybdenum Bronze on Platinum Electrode in Sulfuric Acid Solution

Hydrogen molybdenum bronze (HxMoO3) can be electrodeposited on platinum and oxidized in two steps to the hydrogen molybdenum bronze with less amount of hydrogen HyMoO3 (y<x) and MoO3 when platinum electrode is cycled from -0.2 to 1.3V (vs. SCE) in 0.05 mol/L Na2MoO4 + 0.5 mol/L H2SO4 solution. During the formation of HxMoO3, the electrochemical reduction of molybdate existing in the form of polymolydate is reversible and is about a five-electron transfer reaction.

Sulfur resource recovery based on electrolytic manganese residue calcination and manganese oxide ore desulfurization for the clean production of electrolytic manganese

An environmentally friendly and resource-conserving route to the clean production of electrolytic manganese was developed,in which the electrolytic manganese residue(EMR)was initially calcined for cement buffering;then the generated SO2-containing flue gas was managed using manganese oxide ore and anolyte(MOOA)desulfurization;at last,the desulfurized slurry was introduced to the electrolytic manganese production(EMP).Results showed that 4.0 wt%coke addition reduced the sulfur of calcined EMR to 0.9%,thereby satisfying the cement-buffer requirement.Pilot-scale desulfurization showed that about 7.5 vol%of high SO2 containing flue gas can be cleaned to less than 0.1 vol%through a five-stage countercurrent MOOA desulfurization.The desulfurized slurry had 42.44 g·L-Mn2+and 1.92 g·L-1 S2 O62-,which was suitable for electrowinning after purification,and the purity of manganese product was 99.93%,satisfy the National Standard of China YB/T051-2015.This new integrated technology fulfilled 99.7%of sulfur reutilization from the EMR and 94.1%was effectively used to the EMP.The MOOA desulfurization linked the EMP a closed cycle without any pollutant discharge,which promoted the cleaner production of EMP industry.

Interfacial Behavior of Sulfur and Yttrium in Yttrium Modified Ni _3Al Based Alloy IC6 during High Temperature Oxidation Process

The interfacial behavior of sulfur and yttrium in the yttrium modified Ni 3Al based alloy IC6 during oxidation at 1100 ℃ was analyzed by X ray line scan of electron probe microstructural analysis(EPMA). The results show that the migration and segregation of sulfur to the interface between oxide scale and the substrate at high temperature is retarded owing to the presence of yttrium. This is attributed to the desulfurization by yttrium in the melt and the trapping of sulfur by yttrium rich phases during oxidation, which leads to improving the coherence between oxide scale and substrate. Another reason of increasing the high temperature oxidation resistance of alloy IC6 by the addition of yttrium is that yttrium migrates to the grain boundaries of oxides during oxidation and hence improve their strength. This results in the transformation of the oxide scale spallation cracks from intergranular cracks for alloy without yttrium to transgranular ones for yttrium modified alloy.

Study on experiment and mechanism of thermal dissolved sulfuration of low grade lead-zinc oxide ore in lanpin

The thermal dissolved sulfuration technology is brought forward and performed based on the characteristic of low grade lead-zinc oxide ore in lanpin. Using sulfur as the sulphidizing agent in the experiment, the oxides in the sandstone and ignimbrite are changed into sulfides. The disproportionation reaction of sulfur in a solution is confirmed as 4S＋3H2O=2S^2-＋S2O3^2--＋6H^＋. The dynamics process is studied and the first-order reaction rate equation -1n（1-a）=ktt is obtained. The effects of the reactive products, stirring speed, dosage of sulfuration agent, value of pH and sulphidizing temperature on the sulfuration of oxide ore are investigated. The results indicate that the reactive apparent activation energy is 100.8 kJ/mol and the sulfuration ratio of lead-zinc oxide ore reaches 60% under the conditions of pH 5.9-7.5, the sulfuration temperature of 130 ℃, sulfuration time of 180 min and the stirring speed of 800 r/min.

Agglomeration and leaching behaviors of copper oxides with different chemical binders

The chemical binder is one of the critical factors affecting ore agglomeration behavior and leaching efficiency.In this study,we in-vestigated the effect of the type of binder and mass fraction of the H_(2)SO_(4)solution used on the curing,soaking,and leaching behavior of ag-glomerations.The results revealed that Portland cement(3CaO·SiO_(2),2CaO·SiO_(2),and 3CaO·Al_(2)O_(3))was the optimal binder for obtaining a well-shaped,stable agglomeration structure.A higher extraction rate was achieved when using Portland cement than that obtained using sodi-um silicate,gypsum,or acid-proof cement.An excessive geometric mean size is not conducive to obtaining well-shaped agglomerations and desirable porosity.Using computed tomography(CT)and MATLAB,the porosity of two-dimensional CT images in sample concentrations L1-L3 was observed to increase at least 4.5vol%after acid leaching.Ore agglomerations began to be heavily destroyed and even to disinteg-rate when the sulfuric acid solution concentration was higher than 30 g/L,which was caused by the excessive accumulation of reaction products and residuals.

Effects of selenium and sulfur on antioxidants and physiological parameters of garlic plants during senescence

A hydroponic study was conducted to determine the effects of selenium（Se： 0, 3, 6 μmol L^-1） on senescence-related oxidative stress in garlic plants grown under two sulfur（S） levels. We evaluated the yields of plants harvested at 160 and 200 days after sowing. Plants grown under a low Se dose（0.3 μmol L^-1） at low S level showed higher yields（12.0% increase in fresh weight yield, 13.7% increase in dry weight yield） than the controls, despite a decrease in chlorophyll concentration. Compared with control plants, the Se-treated plants showed lower levels of lipid peroxidation. The Se-treated plants also showed higher activities of glut athione peroxidase and catalase, but lower superoxide dismutase activities. Changes in Fv/Fm values and proline contents were affected more strongly by S than by Se. On the basis of our results, we can conclude that Se plays a key role in the antioxidant systems in garlic seedlings. It delays senescence by alleviating the peroxide stress, but it can be toxic at high levels. A high S level may increase tolerance to high Se concentrations through reducing Se accumulation in plants.