Zonal activation of molecular carbon dioxide and hydrogen over dual sites Ni-Co-MgO catalyst for CO_(2) methanation:Synergistic catalysis of Ni and Co species

An in-depth mechanism in zonal activation of CO_(2)and H2molecular over dual-active sites has not been revealed yet.Here,Ni-Co-MgO was rationally constructed to elucidate the CO_(2)methanation mechanism.The abundant surface nickel and cobalt components as active sites led to strong Ni-Co interaction with charge transfer from nickel to cobalt.Notably,electron-enriched Coδ-species participated in efficient chemisorption and activation of CO_(2)to generate monodentate carbonate.Simultaneously,plentiful available Ni0sites facilitated H2dissociation,thus CO_(2)and H2were smoothly activated at zones of Coδ-species and Ni0,respectively.Detailed in situ DRIFTS,quasi situ XPS,TPSR,and DFT calculations substantiated a new formate evolution mechanism via monodentate carbonate instead of traditional bidentate carbonate based on synergistic catalysis of Coδ-species and Ni0.The zonal activation of CO_(2)and H2by tuning electron behaviors of double-center catalysts can boost heterogeneous catalytic hydrogenation performance.

Effect of K_(2)CO_(3) doping on CO_(2) sorption performance of silicate lithium-based sorbent prepared from citric acid treated sediment

In this paper,a low-cost and environmental-friendly leaching agent citric acid(C_(6)H_(8)O_(7))was used to treat the sediment of Dianchi Lake(SDL)to synthesize lithium silicate(Li_(4)SiO_(4))based CO_(2)sorbent.The results were compared with that treated with strong acid.Moreover,the effects of preparation conditions,sorption conditions and desorption conditions on the CO_(2)sorption performance of prepared Li_(4)SiO_(4)were systematically studied.Under optimal conditions,the Li_(4)SiO_(4)sorbent was successfully synthesized and its CO_(2)sorption capacity reached 31.37%(mass),which is much higher than that synthesized from SDL treated with strong acid.It is speculated that the presence of some elements after C_(6)H_(8)O_(7)treatment may promote the sorption of synthetic Li_(4)SiO_(4)to CO_(2).In addition,after doping with K_(2)CO_(3),the CO_(2)uptake increases from the original 12.02%and 22.12%to 23.96%and 32.41%(mass)under the 20%and 50%CO_(2)partial pressure,respectively.More importantly,after doping K_(2)CO_(3),the synthesized Li_(4)SiO_(4)has a high cyclic stability under the low CO_(2)partial pressure.

High-performance liquid-phase catalytic purification of phosphine in tail gas using Pd(Ⅱ)/Cu(Ⅱ)composite

Pd/Cu liquid-phase composite was utilized as the catalyst in this study to remove PH_(3) at low temperatures.The anti-heterotoxicity of catalysts in the PH_(3) catalytic oxidation purification process was carefully explored and pioneered.The catalytic performance,thermodynamics,kinetics,and catalytic oxidation mechanism of Pd/Cu liquid-phase catalyst catalytic oxidation of PH_(3) were thoroughly investigated.The results showed that Pd/Cu has a superior catalytic effect on the removal of PH_(3) in the gas mixture under low temperature.With CO as the carrier gas,the removal efficiency of PH_(3) could be maintained at 100%for nearly 450 min,indicating that the Pd/Cu liquid phase catalyst has good resistance to heterotoxicity.According to the thermodynamic,kinetic,and related characterization results of the PH_(3) purification process,the kinetic region of the gas–liquid reaction of PH_(3) absorption by Pd/Cu solution was an interfacial reaction.Pd was the primary catalyst and Cu was the secondary catalyst,and the adsorption of PH_(3)was a primary reaction.PH_(3) was spontaneously oxidized to H_(3)PO_(4) in the Pd/Cu catalytic system during the removal process.Pd was regenerated by O_(2) and Cu,increasing the activity and stability of the Pd/Cu catalyst in the sustain and efficient purification of PH_(3) in tail gas.

Unravelling the nature of the active species as well as the Mn doping effect over gamma-Al_(2)O_(3) catalyst for eliminating AsH_(3) and PH_(3)

To investigate the enhancing effect of Mn on the performance of simultaneous catalytic oxidation of AsH_(3)and PH_(3)by CuO-Al_(2)O_(3)in a reducing atmosphere under micro-oxygen conditions,Cu-Mn modifiedγ-Al_(2)O_(3)catalysts were prepared.The characteristics of the catalysts showed that Mn reduced the crystallinity of the active CuO component,increased the number of oxygen vacancies and acidic sites on the catalyst surface,enhanced the mobility of surface oxygen,and the interaction between copper and manganese promoted the redox cycling ability of the catalysts and improved their oxidation performance,which increased the conversion frequency(TOF)by 2.54×10^(-2)to 3.07×10^(-2)sec^(-1).On the other hand,the introduction of Mn reduced the production of phosphate and As_(2)O_(3)on the catalyst surface by30.96%and 44.9%,which reduced the coverage and inerting of the active sites by phosphate and As_(2)O_(3),resulting in an 8 hr(6 hr)improvement in the stability of PH_(3)(AsH_(3))removal.

Simultaneous catalytic hydrolysis of carbonyl sulfide and carbon disulfide over Al_2O_3-K/CAC catalyst at low temperature

In this work, a series of coal-based active carbon （CAC） catalysts loaded by A1203 were prepared by sol-gel method and used for the simulta- neous catalytic hydrolysis of carbonyl sulfide （COS） and carbon disulfide （CS2） at relatively low temperatures of 30-70 ℃. The influences of calcinations temperatures and operation conditions such as： reaction temperature, 02 concentration, gas hourly space velocity （GHSV） and relative humidity （RH） were also discussed respectively. The results showed that catalysts with 5.0 wt% A1203 calcined at 300 ℃ had supe- rior activity for the simultaneous catalytic hydrolysis of COS and CS2. When the reaction temperature was above 50 ℃, catalytic hydrolysis activity of COS could be enhanced but that of CS2 was inhibited. Too high RH could make the catalytic hydrolysis activities of COS and CS2 decrease. A small amount of 02 introduction could enhance the simultaneous catalytic hydrolysis activities of COS and CS2.

Lactation mastitis: Promising alternative indicators for early diagnosis

Although lactation mastitis(LM)has been extensively researched,the incidence rate of LM remains a salient clinical problem.To reduce this incidence rate and achieve a better prognosis,early and specific quantitative indicators are particularly important.It has been found that milk electrolyte concentrations(chloride,potassium,and sodium)and electrical conductivity(EC)significantly change in the early stages of LM in an animal model.Several studies have evaluated EC for the detection of subclinical mastitis in cows.EC,chloride,and sodium content of milk were more accurate for predicting infection status than were other variables.In the early stages of LM,lactic sodium,chloride,and EC increase,but potassium decreases.However,these indicators have not been reported in the diagnosis of LM in humans.This review summarizes the pathogenesis and the mechanism of LM in terms of milk electrolyte concentration and EC,and aim to provide new ideas for the detection of sub-clinical mastitis in humans.

CeO_(2)-supported Fe,Co and Ni toward CO_(2) hydrogenation:Tuning catalytic performance via metal-support interaction

The chemical transformation of CO_(2) produces carbon compounds that can be used as precursors for the production of chemicals and fuels.Here,we investigated the activity and selectivity of the transition metals(Fe,Co,and Ni)supported on CeO_(2) catalyst for CO_(2) hydrogenation at atmospheric pressure.We found that Ni/CeO_(2) shows the highest CO_(2)conversion compared with Fe/CeO_(2) and Co/CeO_(2).Besides,Co/CeO_(2)and Ni/CeO_(2) exhibit nearly 100%CH_(4)selectivity while Fe/CeO_(2) inclines to produce CO.The characterization results show that the metal-support interaction order is Fe/CeO_(2)>Co/CeO_(2)>Ni/CeO_(2),the weak metal-support inte raction over Ni/CeO_(2)benefits the activation of H_(2) and then promotes the activity of CO_(2) hydrogenation.Additionally,in situ DRIFTS results demonstrate that monodentate formate species rather than bidentate formate are the active intermediates.The main route of CO_(2) hydrogenation to CH_(4) is that CO_(2) is firstly transformed to m-HCOO*and then direct hydrogenation of the m-HCOO*to CH_(4).This study provides insights into the understanding of the mechanisms of CO_(2) hydrogenation on CeO_(2)based catalysts.

Boosting the catalytic performance of Cu-SAPO-34in NO_(x) removal via hydrothermal treatment

Phosphate ions promoted Cu-SAPO-34(P-Cu-SAPO-34)were prepared using bulk CuO particles as Cu^(2+)precursor by a solid-state ion exchange technique for the selective catalytic reduction of NO_(x) with NH_3(NH_3-SCR).The effects of high temperature(H-T)hydrothermal aging on the NO_(x) removal(de-NO_(x))performance of Cu-SAPO-34 with and without phosphate ions were systematically investigated at atomic level.The results displayed that both Cu-SAPO-34 and P-Cu-SAPO-34 presented relatively poor NO_(x) removal activity with a low conversion(<30%)at 250-500℃.However,after H-T hydrothermal treatment(800℃ for 10 hr at 10%H_2O),these two samples showed significantly satisfied NO_(x) elimination performance with a quite high conversion(70%-90%)at 250-500℃.Additionally,phosphate ions decoration can further enhance the catalytic performance of Cu-SAPO-34 after hydrothermal treatment(Cu-SAPO-34H).The textural properties,morphologies,structural feature,acidity,redox characteristic,and surface-active species of the fresh and hydrothermally aged samples were analyzed using various characterization methods.The systematical characterization results revealed that increases of 28%of the isolated Cu^(2+)active species(Cu^(2+)-2Z,Cu(OH)^(+)-Z)mainly from bulk CuO and 50%of the Bronsted acid sites,the high dispersion of isolated Cu^(2+)active component as well as the Bronsted acid sites were mainly responsible for the accepted catalytic activity of these two hydrothermally aged samples,especially for P-Cu-SAPO-34H.

Advances in selective catalytic oxidation of ammonia (NH_(3)-SCO): A review of catalyst structure-activity relationship and design principles

NH_(3) in ambient air directly leads to an increase in the aerosol content in the air. These substances lead to the formation of haze to various environmental problems after atmospheric circulation and diffusion. Controlling NH_(3) emissions caused by ammonia escaping from mobile and industrial sources can effectively reduce the NH_(3) content in ambient air. Among the various NH_(3) removal methods, the selective catalytic oxygen method (NH_(3)-SCO) is committed to oxidizing NH_(3) to environmentally harmless H_(2)O and N_(2);therefore, it is the most valuable and ideal ammonia removal method. In this review, the characteristics of loaded and core-shell catalysts in NH_(3)-SCO have been reviewed in the context of catalyst structure-activity relationships, and the H_(2)O resistance and SO2 resistance of the catalysts are discussed in the context of practical application conditions. Then the effects of the valence state of the active center, oxygen species on the catalyst surface, dispersion of the active center and acidic sites on the catalyst performance are discussed comprehensively. Finally, the shortcomings of the existing catalysts are summarized and the catalyst development is discussed based on the existing studies.

High efficiency removal of NO using waste calcium carbide slag by facile KOH modification

Waste calcium carbide slags(CS),which are widely applied to desulfurisation,are not typically used in denitration.Herein,to well achieve waste control by waste,a facile and highefficiency denitration strategy is developed using KOH to modify the calcium carbide slags(KCS).Various KCS samples were investigated using a series of physical and chemical characterisations.The performance test results showed that the KOH concentration and reaction temperature are the main factors affecting the denitration efficiency of KCS,and CS modified with 1.5 mol/L KOH(KCS-1.5)can achieve 100% denitration efficiency at 300℃.Such excellent removal efficiency is due to the catalytic oxidation of the oxygen-containing functional groups derived from the KCS.Further studies showed that KOH treatment significantly increased the concentration of oxygen vacancies,nitro compounds,and basic sites of CS.This study provides a novel strategy for the resource utilisation of waste CS in the future.

Cu/ACF adsorbent modified by non-thermal plasma for simultaneous adsorption–oxidation of H_(2)S and PH_(3)

Non-thermal plasma(NTP)surface modification technology is a new method to control the surface properties of materials,which has been widely used in the field of environmental protection because of its short action time,simple process and no pollution.In this study,Cu/ACF(activated carbon fiber loaded with copper)adsorbent was modified with NTP to remove H_(2)S and PH_(3) simultaneously under low temperature and micro-oxygen condition.Meanwhile,the effects of different modified atmosphere(air,N_(2) and NH_(3)),specific energy input(0–13 J/mL)and modification time(0–30 min)on the removal of H_(2)S and PH_(3) were investigated.Performance test results indicated that under the same reaction conditions,the adsorbent modified by NH_(3) plasma with 5 J/mL for 10 min had the best removal effect on H_(2)S and PH_(3).CO_(2) temperature-programmed desorption and X-ray photoelectron spectroscopy(XPS)analyzes showed that NH_(3) plasma modification could introduce amino functional groups on the surface of the adsorbent,and increase the types and number of alkaline sites on the surface.Brunauer-Emmett-Teller and scanning electron microscopy showed that NH_(3) plasma modification did not significantly change the pore size structure of the adsorbent,but more active components were evenly exposed to the surface,thus improving the adsorption performance.In addition,X-ray diffraction and XPS analysis indicated that the consumption of active components(Cu and Cu_(2)O)and the accumulation of sulfate and phosphate on the surface and inner pores of the adsorbent are the main reasons for the deactivation of the adsorbent.

Experimental and theoretical studies on NO selective catalytic oxidation over α-MnO_(2)

Based on the experimental and theoretical methods,the NO selective catalytic oxidation process was proposed.The experimental results indicated that lattice oxygen was the active site for NO oxide over the α-MnO_(2)(110) surface.In the theoretical study,DFT (density functional theory) and periodic slab modeling were performed on an α-MnO_(2)(110) surface,and two possible NO oxidation mechanisms over the surface were proposed.The non-defectα-MnO_(2)(110) surface showed the highest stability,and the surface Os(the second layer oxygen atoms) position was the most active and stable site.O_(2)molecule enhanced the joint adsorption process of two NO molecules.The reaction process,including O_(2)dissociation and O=N-O-O-N=O formation,was calculated to carry out the NO catalytic oxidation mechanism over α-MnO_(2)(110).The results showed that NO oxidation over the α-MnO_(2)(110) surface exhibited the greatest possibility following the route of O=N-O-O-N=O formation.Meanwhile,the formation of O=N-O-O-N=O was the rate-determining step.

Enhancement of the electrocatalytic oxidation of antibiotic wastewater over the conductive black carbon-PbO2 electrode prepared using novel green approach

The secondary pollution caused by modification of an electrode due to doping of harmful materials has long been a big concern.In this study,an environmentally friendly material,conductive carbon black,was adopted for modification of lead dioxide electrode(Pb02).It was observed that the as-prepared conductive carbon black modified electrode(C-PbO2)exhibited an enhanced electrocatalytical performance and more stable structure than a pristine Pb02 electrode,and the removal efficiency of metronidazole(MNZ)and COD by a 1.0%C-Pb02 electrode at optimal conditions was increased by 24.66%and 7.01%,respectively.Results revealed that the electrochemical degradation of MNZ wastewater followed pseudo-first-order kinetics.This intimates that the presence of conductive carbon black could improve the current efficiency,promote the generation of hydroxyl radicals,and accelerate the removal of MNZ through oxidation.In addition,MNZ degradation pathways through a C-Pb02 electrode were proposed based on the identified intermediates.To promote the electrode to treat antibiotic wastewater,optimal experimental conditions were predicted through the Box-Behnken design(BBD)method.The results of this study suggest that a C-Pb02 electrode may represent a promising functional material to pretreat antibiotic wastewaters.

Removing carbonyl sulfide with metal-modified activated carbon

A Cu-Co-K/activated carbon （AC） adsorbent has been developed for the removal of carbonyl sulfide （COS）. The effects of COS concentration, reaction temperature and relative humidity were closely examined. A breakthrough of 33.23 mg COS .gl adsorbent at 60℃, under 30% relative humidity and in presence of 1.0% oxygen was exhibited in the Cu-Co-K/AC adsorbent prepared. Competitive adsorption studies for COS in the presence of CS2, and H2S were also conducted. TPD analysis was used to identify sulfur-containing products on the carbon surface, and the results indicated that H2S, COS and SO2 were all evident in the effluent gas generated from the exhausted Cu-Co-K/AC. Structure of the activated carbon samples has been characterized using nitrogen adsorption, and their surface chemical structures were also determined with X-ray photoelectron spectroscopy （XPS）. It turns out that the modification with Cu（OH）2CO3- CoPcS-KOH can significantly improve the COS removal capacity, forming SO2/4 species simultaneously. Regenera- tion of the spent activated carbon sorbents by thermal desorption has also been explored.

Adsorption-oxidation of hydrogen sulfide on Fe/walnut-shell activated carbon surface modified by NH_3-plasma

Walnut-shell activated carbon（WSAC） supported ferric oxide was modified by non-thermal plasma（NTP）, and the removal efficiency for hydrogen sulfide over Fe/WSAC modified by dielectric barrier discharge（DBD） was significantly promoted. The sample modified for10 min and 6.8 k V output（30 V input voltage） maintained 100% H2 S conversion over a long reaction time of 390 min. The surface properties of adsorbents modified by NTP under different conditions were evaluated by the methods of X-ray photoelectron spectroscopy（XPS）, Brunauer–Emmett–Teller（BET） analysis and in-situ Fourier transform infrared spectroscopy（FTIR）, to help understand the effect of the NTP treatment. NTP treatment enhanced the adsorption capacity of Fe/WSAC, which could due to the formation of micro-pores with sizes of0.4, 0.5 and 0.75 nm. XPS revealed that chemisorbed oxygen changed into lattice oxygen after NTP treatment, and lattice oxygen is beneficial for H2 S oxidation. From the in-situ FTIR result,transformation of the reaction path on Fe/WSAC was observed after NTP modification. The research results indicate that NTP is an effective method to improve the surface properties of the Fe/WSAC catalyst for H2 S adsorption-oxidation.

Metal loaded zeolite adsorbents for hydrogen cyanide removal

Metal （Cu, Co, or Zn） loaded ZSM-5 and Y zeolite adsorbents were prepared for the adsorption of hydrogen cyanide （HCN） toxic gas. The results showed that the HCN breakthrough capacity was enhanced significantly when zeolites were loaded with Cu. The physical and chemical properties of the adsorbents that influence the HCN adsorption capacity were analyzed. The maximal HCN breakthrough capacities were about the same for both zeolites at 2.2 mol of HCN/mol of Cu. The Cu2p XPS spectra showed that the possible species present were Cu2O and CuO. The Nls XPS data and FT-IR spectra indicated that CN- would be formed in the presence of Cu＋/Cu2＋ and oxygen gas, and the reaction product could be adsorbed onto Cu/ZSM-5 zeolite more easily than HCN.

Nested hollow architectures of nitrogen-doped carbon-decorated Fe,Co,Ni-based phosphides for boosting water and urea electrolysis

Tailoring the nanostructure/morphology and chemical composition is important to regulate the electronic configuration of electrocatalysts and thus enhance their performance for water and urea electrolysis.Herein,the nitrogen-doped carbon-decorated tricomponent metal phosphides of FeP4 nanotube@Ni-Co-P nanocage(NC-FNCP)with unique nested hollow architectures are fabricated by a self-sacrifice template strategy.Benefiting from the multi-component synergy,the modification of nitrogen-doped carbon,and the modulation of nested porous hollow morphology,NC-FNCP facilitates rapid electron/mass transport in water and urea electrolysis.NC-FNCP-based anode shows low potentials of 248 mV and 1.37 V(vs.reversible hydrogen electrode)to attain 10 mA/cm^(2) for oxygen evolution reaction(OER)and urea oxidation reaction(UOR),respectively.In addition,the overall urea electrolysis drives 10 mA/cm^(2) at a comparatively low voltage of 1.52 V(vs.RHE)that is 110 mV lower than that of overall water electrolysis,as well as exhibits excellent stability over 20 h.This work strategizes a multi-shell-structured electrocatalyst with multi-compositions and explores its applications in a sustainable combination of hydrogen production and sewage remediation.

Surface characterization of metal oxides-supported activated carbon fiber catalysts for simultaneous catalytic hydrolysis of carbonyl sulfide and carbon disulfide

The sol–gel method was used to synthesize a series of metal oxides-supported activated carbon fiber (ACF) and the simultaneous catalytic hydrolysis activity of carbonyl sulfide (COS)and carbon disulfide (CS2) at relatively low temperatures of 60°C was tested.The effects of preparation conditions on the catalyst properties were investigated,including the kinds and amount of metal oxides and calcination temperatures.The activity tests indicated that catalysts with 5 wt.%Ni after calcining at 400°C (Ni(5)/ACF(400)) had the best performance for the simultaneous catalytic hydrolysis of COS and CS2.The surface and structure properties of prepared ACF were characterized by scanning electron microscope-energy disperse spectroscopy (SEM-EDS),Brunauer–Emmett–Teller (BET),X-ray diffraction (XRD),carbon dioxidetemperature programmed desorption (CO2-TPD) and diffuse reflectance Fourier transform infrared reflection (DRFTIR).And the metal cation defects were researched by electron paramagnetic resonance (EPR) method.The characterization results showed that the supporting of Ni on the ACF made the ACF catalyst show alkaline and increased the specific surface area and the number of micropores,then improved catalytic hydrolysis activity.The DRFTIR results revealed that-OH species could facilitate the hydrolysis of COS and CS2;-COO and-C–O species could facilitate the oxidation of catalytic hydrolysate H2S.And the EPR results showed that high calcination temperature conditions provide more active reaction center for the COS and CS2 adsorption.

Characteristics of chemical components in PM2.5 at a plateau city, South-west China

A sampling campaign including summer, autumn and winter of 2014 and spring of 2015 was accomplished to obtain the characteristic of chemical components in PM2.5 at three sites ofKunming, a plateau city in South-west China. Nine kinds of water-soluble inorganic ions （WSI）, organic and element carbon （OC and EC） in PM2.5 were analyzed by ion chromatography and thermal optical reflectance method, respectively. Results showed that the average concentrations of total WSI, OC and EC were 22.85±10.95 μg.m -3, 17.83±9.57 μg.m-3 and 5.114-4.29 μg.m-3, respectively. They totally accounted for 53.0% of PM2.5. Secondary organic and inorganic aerosols （SOA and SIA） were also assessed by the minimum ratio of OC/EC, nitrogen and sulfur oxidation ratios. The annual average concentrations of SOA and SIA totally accounted for 28.3% of the PM2.5 concentration. The low proportion suggested the primary emission was the main source of PM2.5 in Kunming. However, secondary pollution in the plateau city should also not be ignorable, due to the appropriate temperature and strong solar radiation, which can promote the atmospheric photochemical reactions.

Immobilization of NZVI in polydopamine surface-modified biochar for adsorption and degradation of tetracycline in aqueous solution

Polydopamine/NZVl@biochar composite （PDA/NZVI@BC） with high removal efficiency of tetracycline （TC） in aqueous solutions was successfully synthesized, The resultant composite demonstrated high reactivity, excellent stability and reusability over the reaction course. Such excellent performance can be attributed to the presence of the huge surface area on biochar （BC）, which could enhance NZVI dispersion and prolong its longevity. The carbonyl group contained on the surface of bioehar could combine with the amino group on polydopamine（PDA）. The hydroxyl groups in PDA is able to enhance the dispersion and loading of NZVI on BC. Being modified by PDA, the hydrophilicity of biochar was improved. Among BC, pristine NZVI and PDA/NZVI（L-BC, PDA/ NZVI（a-,BC exhibited the highest activity for removal of TC. Compared with NZVI, the removal efficiency of TC could be increased by 55.9c- by using PDA/NZVI@BC under the same conditions. The optimal modification time of PDA was 813, and the ratio of NZVI to BC was 1：2. In addition, the possible degradation mechanism of TC was proposed, which was based on the analysis of degraded praducts by LC-MS. Difli,-rent importanl /actors impacling on TC removal （including mass ratio of NZVI to BC/PDA, initial concentration, pH value and the initial temperature of the solution） were investigated as well. Overall, this study provides a promising alternative material and environmental pollution management option for antibiotic wastewater treatment.