Industrial solid wastes to environmental protection materials for removal of gaseous pollutants:A review

The application of industrial solid wastes as environmentally functional materials for air pollutants control has gained much attention in recent years due to its potential to reduce air pollution in a cost-effective manner.In this review,we investigate the development of industrialwaste-based functional materials for various gas pollutant removal and consider the relevant reaction mechanism according to different types of industrial solid waste.We see a recent effort towards achieving high-performance environmental functional materials via chemical or physical modification,in which the active components,pore size,and phase structure can be altered.The review will discuss the potential of using industrial solid wastes,these modified materials,or synthesized materials from raw waste precursors for the removal of air pollutants,including SO_(2),NO_(x),Hg^(0),H_(2)S,VOCs,and CO_(2).The challenges still need to be addressed to realize this potential and the prospects for future research fully.The suggestions for future directions include determining the optimal composition of these materials,calculating the real reaction rate and turnover frequency,developing effective treatment methods,and establishing chemical component databases of raw industrial solid waste for catalysts/adsorbent preparation.

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.

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.

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.

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.

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.

Regulating the valence and size of the active center of Co/Al_(2)O_(3)catalyst improved the performance and selectivity of NH_(3)-SCO

To improve the activity of Co/Al_(2)O_(3)catalysts in selective catalytic oxidation of ammonia(NH_(3)-SCO),valence state and size of active centers of Al_(2)O_(3)-supported Co catalysts were adjusted by conducting H_(2)reduction pretreatment.The NH_(3)-SCO activity of the adjusted 2Co/Al_(2)O_(3)catalyst was substantially improved,outperforming other catalysts with higher Co-loading.Fresh Co/Al_(2)O_(3)catalysts exhibited multitemperature reduction processes,enabling the control of the valence state of the Co-active centers by adjusting the reduction temperature.Changes in the state of the Co-active centers also led to differences in redox capacity of the catalysts,resulting in different reaction mechanisms for NH_(3)-SCO.However,in situ diffuse reflectance infrared Fourier transform spectra revealed that an excessive O_(2)activation capacity caused overoxidation of NH_(3)to NO and NO_(2).The NH_(3)-SCO activity of the 2Co/Al_(2)O_(3)catalyst with low redox capacity was successfully increased while controlling and optimizing the N_(2)selectivity by modulating the active centers via H_(2)pretreatment,which is a universalmethod used for enhancing the redox properties of catalysts.Thus,this method has great potential for application in the design of inexpensive and highly active catalysts.

Cu/TiO_(2)adsorbents modified by air plasma for adsorption-oxidation of H_(2)S

In this study,non-thermal plasma(NTP)was employed to modify the Cu/TiO_(2)adsorbent to efficiently purify H_(2)S in low-temperature and micro-oxygen environments.The effects of Cu loading amounts and atmospheres of NTP treatment on the adsorption-oxidation performance of the adsorbents were investigated.The NTP modification successfully boosted the H_(2)S removal capacity to varying degrees,and the optimized adsorbent treated by air plasma(Cu/TiO_(2)-Air)attained the best H_(2)S breakthrough capacity of 113.29 mg H_(2)S/gadsorbent,which was almost 5 times higher than that of the adsorbent without NTP modification.Further studies demonstrated that the superior performance of Cu/TiO_(2)-Air was attributed to increased mesoporous volume,more exposure of active sites(CuO)and functional groups(amino groups and hydroxyl groups),enhanced Ti-O-Cu interaction,and the favorable ratio of active oxygen species.Additionally,the X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)results indicated the main reason for the deactivationwas the consumption of the active components(CuO)and the agglomeration of reaction products(CuS and SO_(4)^(2−))occupying the active sites on the surface and the inner pores of the adsorbents.

Effects of biomass co-pyrolysis and herbaceous plant colonization on the transformation of tailings into soil like substrate

Enhancing soil organic matter characteristics,ameliorating physical structure,mitigating heavy metal toxicity,and hastening mineral weathering processes are crucial approaches to accomplish the transition of tailings substrate to a soil-like substrate.The incorporation of biomass co-pyrolysis and plant colonization has been established to be a significant factor in soil substrate formation and soil pollutant remediation.Despite this,there is presently an absence of research efforts aimed at synergistically utilizing these two technologies to expedite the process of mining tailings soil substrate formation.The current study aimed to investigate the underlying mechanism of geochemical changes and rapid mineral weathering during the process of transforming tailings substrate into a soil-like substrate,under the combined effects of biomass co-smoldering pyrolysis and plant colonization.The findings of this study suggest that the incorporation of smoldering pyrolysis and plant colonization induces a high-temperature effect and biological effects,which enhance the physical and chemical properties of tailings,while simultaneously accelerating the rate of mineral weathering.Notable improvements include the amelioration of extreme pH levels,nutrient enrichment,the formation of aggregates,and an increase in enzyme activity,all of which collectively demonstrate the successful attainment of tailings substrate reconstruction.Evidence of the acceleratedweathering was verified by phase and surfacemorphology analysis using X-ray diffraction and scanning electron microscopy.Discovered corrosion and fragmentation on the surface ofminerals.The weathering resulted in corrosion and fragmentation of the surface of the treated mineral.This study confirms that co-smoldering pyrolysis of biomass,combined with plant colonization,can effectively promote the transformation of tailings into soil-like substrates.This method has can effectively address the key challenges that have previously hindered sustainable development of the mining industry and provides a novel approach for ecological restoration of tailings deposits.

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.