Abstract:Anaerobic digestion is a promising technology for the resource recovery from sewage and organic solid waste.Recent studies have shown that conductive materials can enhance anaerobic digestion,but their specific effects on different types of substrates remain unclear.In this study,starch and soy protein isolate were selected as representative substrates for polysaccharides and proteins,and biochar and iron powder were used as conductive materials in biochemical methane potential(BMP)tests,either individually or in combination.The results revealed a distinct double-plateau pattern in methane production from polysaccharides,whereas methane production from proteins was relatively smoother.The kinetics were well described(R2＞0.99)by a combination of two modified Gompertz models,which were then used to analyze methane potential and production rate.The findings indicated that under the mediation of conductive materials,biochar significantly increased the methane potential,whereas the addition of iron powder enhanced the methane production rate.Specifically,the addition of 10 g/L biochar increased the methane potential of polysaccharides from 275.8 mL/g to 292.6 mL/g,and in the protein group,the methane potential increased from 286.7 mL/g to 302.4 mL/g.The addition of iron powder slightly reduced the maximum methane potential of polysaccharides(260.3 mL/g)but had no significant effect on the methane potential of proteins(284.7 mL/g).During the early stages of polysaccharide degradation,pH decreased and butyrate accumulated,while the conductive materials accelerated pH recovery and butyrate degradation.During the protein hydrolysis process,the release of ammonia nitrogen maintained a stable pH,while the addition of iron powder slightly increased the pH.No significant accumulation of volatile fatty acid(VFA)was observed in the protein experiments.Microbial community analysis revealed considerable differences in the inoculated sludge cultured with polysaccharides and proteins.In the protein experimental group,a higher abundance of the hydrogenotrophic methanogen Methanobacterium was observed,suggesting that hydrogen,serving as an electron donor for CO2 reduction,may be the primary pathway for methane production during protein degradation.Iron powder promoted the enrichment of Methanobacterium regardless of the substrate.Additionally,in the polysaccharide experimental group,Clostridium_sensu_stricto_1,a butyrate-producing bacterium,showed significant enrichment,and the addition of biochar,either alone or in combination with iron powder,led to in a notable increase in its abundance.This suggests that biochar facilitated the acidification process during polysaccharide degradation,correlating with the accumulation of VFA.This study elucidates the anaerobic degradation processes of two representative substrates,polysaccharides and proteins,and explores the influence and mechanisms of conductive materials in these processes.The findings provide new insights into enhancing the efficiency of anaerobic conversion.

Abstract:In the context of carbon neutrality and energy transition,the global scale-up and deployment of new energy vehicles(NEVs)are accelerating in terms of both quality and pace.Among the critical power sources for NEVs,lithium-ion batteries stand out as a key component.However,due to degradation,the management of spent batteries poses growing challenges.Simultaneously,in alignment with the strategic objectives of"carbon peak and carbon neutrality",the recyclability of waste materials has attracted widespread interest.Despite this,the recycling of certain biomass waste,such as bamboo powder,kitchen and fruit waste,bagasse,tea leaves,and coffee grounds,faces numerous obstacles.This paper provides a comprehensive review of the application of various waste materials in the recycling of lithium-ion batteries,including reaction mechanisms,pathways,and practical value.Specifically,straw is predominantly used as a reducing agent in acid leaching systems,for the production of biochar,and for the generation of reducing gases.Kitchen waste,exemplified by orange peels,is primarily utilized for the preparation of citric acid,serving as both leaching and reducing agents.Bagasse is mainly employed for the production of glucose as a reducing agent and for the generation of reducing gases.Polyphenols in tea residues can reduce metals within lithium-ion batteries.Furthermore,biomass generates a significant amount of reducing gases during the calcination process,which can enhance the efficiency of reactions by introducing gas-solid interactions into the calcination system.Additionally,the introduction of biochar can effectively reduce carbon emissions in the production process,endowing biomass with unique advantages as a reducing agent in calcination.The extraction of reducing substances or organic acids from biomass can serve as alternatives to environmentally unfriendly reducing agents,such as sodium thiosulfate or inorganic acids,used in hydrometallurgical reduction processes,thereby mitigating the potential environmental impact associated with the recycling of spent lithium-ion batteries.Recycling spent lithium-ion batteries with waste materials circumvents the costs and environmental hazards associated with conventional biomass disposal or recycling.This approach offers a viable strategy for the recycling of spent lithium-ion batteries,holding substantial practical value.Based on state-of-the-art research,this paper evaluates various approaches to recycling lithium-ion batteries using waste materials and provides perspectives and recommendations on the application of different types of waste in the recycling process.The paper also discusses the limitations and countermeasures of using biomass waste in lithium-ion battery recycling,offering new insights into the organic integration of the waste resource industry with the lithium-ion battery recycling sector.

Abstract:The rapid growth of China's tobacco industry leads to a significant increase in tobacco production and processing,inevitably generating substantial tobacco waste.This waste poses both environmental challenges and opportunities for resource utilization.Developing clean and efficient methods to utilize these residues is essential for advancing environmental sustainability and enhancing the economic value of the tobacco industry.One promising approach is the thermochemical conversion of tobacco waste into biochar,which has gained considerable attention as a major strategy for environmental remediation.This review systematically examines the recycling of tobacco waste into biochar-based carbon materials,focusing on thermochemical preparation strategies and their adsorption mechanisms for environmental pollutants in water,air,and soil.Tobacco waste-derived biochars can be classified into three types:pristine,functionalized,and activated biochars,each with distinct physicochemical properties tailored for specific environmental applications.Functionalized and activated biochars demonstrate excellent adsorption performance for airborne contaminants and wastewater pollutants,attributed to mechanisms including electrostatic interactions,surface precipitation,cation-π interactions,ion exchange,and surface coordination.The introduction of functional groups and an increased surface area during activation or functionalization significantly enhances their adsorption capabilities.In contrast,pristine biochars primarily improve soil fertility by enhancing nutrient retention,stimulating microbial activity,and reducing the bioavailability of toxic pollutants,offering an eco-friendly solution for sustainable agriculture.The adsorption capacity of tobacco waste-derived biochars is closely linked to key physicochemical properties,including pore structure,surface functional groups,heteroatom doping,graphitization degree,and aromatic ring carbon structure.Understanding these structural characteristics allows researchers to tailor biochar properties for specific environmental applications.However,challenges remain.Precisely controlling biochar properties during thermochemical conversion and scaling up production methods are key areas needing further attention.Future studies should focus on deepening our understanding of the"preparation-structure-effect"relationship and elucidating fundamental adsorption mechanisms.A top-down strategic approach,incorporating innovative activation techniques,optimized process parameters,and hybrid biochar materials,could further enhance adsorption performance and expanding potential applications.Efficiently converting tobacco waste into high-performance adsorbents will contribute to sustainable waste management,environmental protection,and the circular economy.

Abstract:The widespread use of plastics results in the annual generation of large amounts of waste,posing significant environmental challenges due to inefficient treatment and the resulting pollution.Therefore,the development of green and efficient recycling methods is crucial.Hydrolysis offers a promising strategy for the degradation and recycling of polyester plastics,producing either monomers or high-value-added chemicals.Polycaprolactone(PCL),a biodegradable alkyl polyester synthesized via ring-opening polymerization of the ε-caprolactone monomer,possesses desirable mechanical properties and biocompatibility,yet its recovery rate remains low.This work demonstrates the efficient hydrolysis of PCL under solvent-free conditions using a cost-effective cobalt phosphine complex and a metal trifluoromethanesulfonate as co-catalysts.Gas chromatography(GC)and proton nuclear magnetic resonance(1H NMR)spectroscopy were used to analyze the reaction products.We investigated the effects of hydrogen pressure and temperature,optimizing reaction conditions:160 ℃,6 MPa hydrogen pressure,10％Co(OAc)2-triphos(1,1,1-tris(diphenylphosphinomethyl)ethane),and 10％Sc(OTf)3(scandium trifluoromethanesulfonate)for 12 h.Under these conditions,1,6-hexanediol was produced with 99％conversion and 99％yield.Even at reduced pressure(2 MPa)and catalyst loadings(1％each),99％conversion and 97％yield were achieved.1,6-hexanediol is a valuable fine chemical and an important intermediate.Catalyst recovery studies revealed limited recyclability.Mechanistically,the strong Lewis acidity of metal trifluoromethanesulfonates facilitates rearrangement,whereas weaker Lewis acids merely reduce the influence of the carbonyl group.The Co(OAc)2-triphos system catalyzes carbonyl hydrogenation,unlike the Ni(OAc)2-triphos system,which only hydrogenates C=C double bonds.Therefore,the Co(OAc)2-triphos/Sc(OTf)3 catalyst system first promotes the hydrogenation of PCL to form a hemiacetal,followed by intramolecular 1,3-hydrogen transfer,depolymerizing PCL into 6-hydroxyhexanal,which is subsequently hydrogenated to produce 1,6-hexanediol.This work provides a feasible strategy for enhancing the recycling of discarded PCL plastics,contributing to efforts to address the environmental challenges posed by plastic waste.

Abstract:Microreactors,known for their superior mixing performance and efficient mass transfer characteristics,are widely used in many fields,such as chemical production,drug synthesis,and energy conversion.This study focuses on the design of microchannel structures and explores the underlying mechanisms of mass transfer enhancement by the passive microreactors.Four types of microreactor designs were investigated,including butterfly microchannel,Tesla microchannel,snake microchannel,and herringbone microchannel,and their mixing performance was systematically evaluated.Both numerical simulations and experimental tests were employed,and key parameters,such as mixing efficiency(η)and segregation index(Xs),were used to evaluate the mixing performance.The effects of Reynolds number(Re)and fluid viscosity on mixing efficiency and pressure drop are analyzed in detail.Numerical simulations suggest that each microchannel design enhances mass transfer through different underlying mechanisms.The butterfly microchannel achieves efficient fluid dispersion and recombination by introducing obstacles;the Tesla microchannel facilitates fluid collision and flow interlacing through counterflow;the snake microchannel induces velocity differences and secondary flows via curved flow paths;the herringbone microchannel generates transverse secondary convections by incorporating grooves on the inner walls.The four microchannels all significantly improve the mixing performance of the microreactors,with butterfly and Tesla microchannels showing better mixing performance at low Re and snake and herringbone microchannels exhibiting lower pressure drops at high Re.Numerical simulations also demonstrate that the dominant mode of mass transfer shifts from molecular diffusion to convective transfer as Re increases.The mixing performance is poor when Re is low,as evidenced by the large segregation index and low mixing efficiency,and mass transfer mainly relies on molecular diffusion at low Re.The mixing performance gradually improves as Re increases,as indicated by the decreased segregation index and increased mixing efficiency,suggesting that the dominant mode of mass transfer shifts from molecular diffusion to convective transfer at high Re.In addition,the impact of fluid viscosity on mixing performance predicted by numerical simulations suggests that the mixing efficiency is weakened as fluid viscosity increases.The simulation results were further validated by experiments.Experimental results confirm that microchannel structures have a significant impact on the mixing performance at low Re,and the butterfly microchannel shows better mixing performance than the snake microchannel.In conclusion,experimental tests and numerical simulations show consistent results on the dependence of mixing performance on Re,the influence of microchannel structure on mixing performance,and the underlying mechanisms of mass transfer enhancement.This study provides theoretical guidance and experimental support for the design and optimization of efficient microreactors,offering valuable insights for practical applications.

Abstract:Immobilized microbial technology offers advantages such as strong resistance to toxicity,improved stability,and superior degradation performance.This study developed an innovative embedding-crosslinking co-immobilization strategy using sodium alginate(SA),chitosan(CS),and biochar(BC)to construct SA/CS@BC composite microspheres for encapsulating the deep-sea phenol-degrading bacterial consortium SP-1.Key parameters were optimized through single-factor experiments:SA concentration(1.0％,2.0％,3.0％,4.0％,5.0％),CS concentration(0.25％,0.5％,0.75％,1.0％,1.25％),CaCl2 crosslinker concentration(1.0％,2.0％,3.0％,4.0％,5.0％),and BC dosage(0.25％,0.5％,0.75％,1.0％,1.25％).Following degradation screening at 800 mg/L phenol,the performances of free bacteria,SA/CS microspheres,and SA/CS@BC microspheres were comparatively analyzed at phenol concentrations of 200,400,600,800,1 000,and 1 200 mg/L.The underlying mechanisms were investigated using SEM for microstructural morphology,FTIR for functional group analysis,the BET method for specific surface area measurement,LC-MS for metabolic intermediate identification,TOC analysis for mineralization quantification,and 5-cycle reuse tests for operational stability assessment.The optimized SA/CS@BC microspheres at 3.0％SA,0.75％CS,4.0％CaCl2,and 1.00％BC achieved a 94.6％degradation rate at 1 200 mg/L phenol,which was 3.3-fold higher than that of free bacteria and 76.2％higher than that of SA/CS microspheres.At 1 000 mg/L,SA/CS@BC maintained 95.2％efficiency,significantly exceeding that of SA/CS microspheres and free bacteria.BC incorporation increased the specific surface area from 4.936 m2/g to 32.829 m2/g;SEM confirmed the dense colonization of SP-1 within the BC porous architecture,whereas SA/CS microspheres exhibited a compact structure with sparse microbial loading.FTIR spectra revealed intensified absorption peaks at 3 335 cm-1(-OH),1 590 cm-1(—COOH),and 1 004 cm-1(C—O-C)for SA/CS@BC,with blue shifts compared to SA/CS(3 420 cm 1,1 622 cm 1,1 024 cm 1),indicating enhanced hydrogen-bonding networks.Elevated functional group abundance and strengthened hydrogen bonds jointly promoted phenol adsorption.LC-MS detected key intermediates including catechol,muconic acid,and succinic acid.Phenol was first hydroxylated to catechol,followed by ortho-cleavage of catechol to form muconic acid,which was further oxidized to succinic acid entering the tricarboxylic acid cycle,and ultimately mineralized to CO2 and H2O.TOC analysis demonstrated 93.9％removal after 9 days treatment at 1 200 mg/L phenol,with the IC/TC ratio increasing from 5.8％to 68.5％,verifying complete mineralization to CO2 and H2O.SA/CS@BC microspheres retained 90.5％degradation efficiency after 5 reuse cycles at 1 200 mg/L phenol.This work demonstrates that SA/CS@BC microspheres enhance phenol degradation:the SA/CS hydrogel shields microbes from acute phenol toxicity;BC rapidly concentrates phenol,while SA/CS gel controls the gradual release to maintain sub-inhibitory concentrations.BC's pores increase microbial loading density,and surface oxygen groups facilitate microbe-pollutant interactions.This technology provides an efficient,stable,and engineerable solution for bioaugmentation of high-concentration phenol-laden wastewater.

Abstract:To develop a micro-combustion system for carbon-free fuels,a micro pure-hydrogen swirl combustor was designed and tested.This combustor operates efficiently across a wide range of equivalence ratios and input power levels and can seamlessly switch between gaseous hydrocarbon fuels and pure hydrogen.The combustor features a non-premixed combustion mode and a low-flow-resistance design,incorporating integrated swirl blades and a preheated annular flow channel.The swirl number is 0.76,with flow resistance of less than 86 Pa.The aerodynamic characteristics of the micro-swirl combustor were explored through numerical simulations.The results demonstrate that well-distributed high-velocity zones and recirculation regions are formed at the combustor outlet.The central recirculation zone exhibits an axisymmetric distribution,effectively entraining downstream hot flue gases and thereby achieving stable swirl combustion.Experimental investigations were carried out to study the effects of the equivalence ratio(0.3-0.6)and input power(495-990 W)on the temperature distributions and pollutant emissions of pure-hydrogen combustion.The results show that the developed micro-swirl combustor operates efficiently and stably within the tested equivalence ratio range.When the input power is 990 W,the average temperatures measured at seven monitoring points at equivalence ratios of 0.3,0.4,0.5,and 0.6 are 1 182,1 277,1 376,and 1 256 K,respectively.The highest flue gas temperature is achieved at an equivalence ratio of 0.5,with a maximum measured temperature of 1 579 K.The input power has a significant impact on the flue gas temperature,with higher heat release rates resulting in increased temperatures.At an equivalence ratio of 0.5 and a heat release rate of 0.62 MW/m2,the NO emission concentration reaches 140.6 mg/m.Reducing the equivalence ratio while maintaining the same heat release rate significantly lowers NO emissions.For instance,at an equivalence ratio of 0.3 and an input power of 990 W,the NO concentration drops to 60.3 mg/m3,representing a 56.2％reduction while maintaining complete hydrogen combustion.The flame of pure hydrogen appears transparent and is difficult to observe with the naked eye under illuminated environments.In the absence of ambient light,it exhibits weak luminescence primarily caused by combustion intermediates,manifesting as an orange-red color.Surrounding this orange-red region,a faint bluish-purple hue can be observed.The height of pure hydrogen flame increases continuously with increasing input power.When the input power reaches 495 W,the hydrogen flame becomes anchored at the exit of the micro-swirl combustor.At an elevated input power of 990 W,the flame height exceeds 3 cm with stable combustion.

Abstract:The anammox autotrophic denitrification process has distinctly low-carbon characteristics,and the addition of carriers to form biofilm is a common strategy for achieving anammox in mainstream municipal wastewater.However,relatively few studies have been conducted on the evolution of the microbial community structure and functions during anammox biofilm formation under low-temperature and low-substrate conditions.Therefore,in this study,an anammox sludge-biofilm system was first established under low-substrate conditions with NH4+-N of(32.6±2.4)mg/L and NO2--N of(43.9±1.9)mg/L.The evolution of microbial community structure and functions during the formation of anammox biofilm was thoroughly investigated.The results showed that anammox biofilms could form in about 20 days under low-substrate concentrations,and the total nitrogen removal efficiency of the reaction system could be maintained at 67.1％±2.5％.The addition of carriers provided a diverse ecological niche for the anammox sludge and significantly increased the species richness and diversity of the sludge-biofilm system.The addition of carriers also played a selective role in the anammox bacterial community.The relative abundance of the filamentous Chloroflexi,which served as a structural skeleton,decreased from 20.9％in the seed sludge to 18.6％.In contrast,the relative abundances of norank_f＿norank_o＿norank_c＿WWE3 and norank_f＿AKYH767 increased significantly from 1.9％and 0 to 13.8％and 7.6％,respectively.The results of β-nearest taxon index also demonstrated that the low-substrate conditions and the addition of carriers increased the role of homogeneous selection in the process of microbial community construction.In addition,the formation of biofilm enhanced the metabolic functions of anammox communities related to cell growth,such as amino acid metabolism,translation,replication and repair,nucleotide metabolism,and cell growth and death.At the same time,it also strengthened ecological functions such as denitrification,nitrate respiration,nitrate reduction,and processes related to the carbon cycle.However,metabolic functions such as energy metabolism,membrane transport and signal transduction related to information exchange,as well as nitrogen respiration,nitrite respiration,anammox function,and ecological functions related to the sulfur cycle,were significantly reduced.

Abstract:The bio-natural gas industry is currently experiencing rapid development in China.Bio-natural gas is purified from biogas,which is produced by anaerobic fermentation of biomass.China's coastal regions possess abundant seaweed resources,a type of biomass with great potential for biogas production.Therefore,this research investigated biogas production from seaweed through anaerobic fermentation,with the aim of effectively utilizing seaweed and recycling biogas as a renewable energy source.Nano-magnetite was added to the anaerobic reactors to explore the potential to enhance biogas production.The results showed that nano-magnetite could accelerate the degradation of biomass and the production of methane.The removal efficiencies of total chemical oxygen demand(TCOD)and soluble chemical oxygen demand(SCOD)in nano-magnetite reactors increased by about 20％and 12％,respectively,compared with the control reactor,which showed removal efficiencies of 51.4％and 42.5％,respectively.Methane production in nano-magnetite reactors more than doubled,with the highest methane production of 1 320 mL at a nano-magnetite concentration of 2.0 g/L.Nano-magnetite enhanced the stability of the anaerobic system and promoted a quicker recovery to neutral pH following acidogenic fermentation of kelp.The pH level in nano-magnetite reactors was always higher than 6.2 and increased gradually to 7.5,while that in the control reactor decreased below 6.0 and then recovered slowly.Analysis of the microbial community structure indicated that nano-magnetite significantly accelerated the enrichment of electroactive microorganisms and facilitated direct interspecies electron transfer(DIET)in methane production.Scanning electron microscopy(SEM)showed that microorganisms and nano-magnetite adhered to each other in nano-magnetite reactors,which was beneficial for DIET to occur among electroactive microorganisms and between electroactive microorganisms and nano-magnetite during the anaerobic methane production process.High-throughput sequencing analysis showed that the electroactive microorganisms were distinctly enriched in nano-magnetite reactors.The abundance of norank_Anaerolineaceae(31.3％,43.4％,47.0％,and 42.1％for 0.2-5.0 g/L nano-magnetite);norank_Bacteroidetes_vadinHA17(2.0％,9.3％,7.6％,and 7.8％);Leptolinea(2.6％,7.3％,6.7％,and 9.1％);Longilinea(2.9％,4.6％,4.8％,and 4.7％);Dechloromonas(2.3％,2.0％,1.2％,and 0.9％);and unclassified_Anaerolineaceae(9.2％,8.9％,8.5％,and 7.1％)all increased compared with the control reactor(17.3％,1.4％,1.6％,3.2％,0.6％,and 2.0％).Additionally,nano-magnetite increased the abundance of the Methylene-H4MPT reductase regulator gene(mer)and the heterodisulfide reductase regulator gene(hdrABC)in methanogens,enhancing the metabolic pathway of DIET methanogenesis.The abundance of mer was 4.57E-04,5.45E-04,5.75E-04,and 5.50E-04,and hdrABC was 3.69E-05,1.06E-04,1.04E-04,and 1.42E-04,while these values in the control reactor were 2.22E-04 and 6.48E-05,respectively.These findings suggest that nano-magnetite significantly enhances biogas production from seaweed biomass.This technology holds promise for further development to support the advancement of the biogas industry and contribute to achieving the"dual carbon"goal in China.

Abstract:The emission of dioxins(PCDD/Fs)from iron and steel sintering flue gas poses a serious threat to regional air quality and human health.The process is considered a major source of dioxins.Therefore,it is necessary to select a cost-effective,environmentally friendly,and efficient control technology for enterprises.To control the formation and emission of sintered dioxins,it is essential to clarify the formation mechanisms of dioxins during the sintering process.Additionally,understanding the formation and distribution of sintered dioxins and their homologues is crucial for regulating emissions at the source,during the process,and at the end-of-pipe.The complexity of the sintering process makes it difficult to study the formation mechanisms of sintered dioxins.However,current research indicates that the formation mechanisms of sintered dioxins mainly include the de novo synthesis mechanism and precursor synthesis mechanism.Since the sintering process meets the basic conditions for the de novo synthesis of dioxins:a carbon source,a chlorine source,and a metal catalyst,a consensus suggests that the primary formation mechanism of sintered dioxins is the de novo synthesis mechanism.Concerning the generation and distribution of PCDD/Fs and their homologues,researchers have sampled and analyzed iron and steel sintering plants worldwide.The results indicate that the products of sintered dioxins are primarily PCDFs,with a smaller proportion of PCDDs,which further supports the conclusion that the de novo synthesis mechanism is the dominant formation pathway for sintered dioxins.For the control of already-formed dioxins,strategies can be categorized into source control,process control,and end-of-pipe treatment.Source control is the most effective approach for reducing dioxin formation and includes measures such as raw material screening and the addition of inhibitors.Process control involves optimizing the sintering process,controlling the sintering temperature zone,and implementing synergistic solid waste treatment.Among these,the synergistic treatment of solid waste is a promising area for future research due to its significant potential.End-of-pipe treatments include high-efficiency dust removal systems,activated carbon adsorption technology,and selective catalytic oxidation technology.However,the application of high-efficiency dust removal and activated carbon adsorption technologies is limited due to economic limitations and technical constraints.Selective catalytic oxidation,on the other hand,has strong potential owning to its operational simplicity and lack of secondary pollution.The selection of an appropriate catalyst is crucial for the successful application of selective catalytic oxidation technology.Future research should focus on developing catalysts with high efficiency,stability,and cost-effectiveness,since no single solution is sufficient for dioxin control.Each control technology has its own limitations.Only by integrating multiple control technologies,methods,and processes adapted to specific conditions can optimal results be achieved.The control paradigm of waste treatment,solid waste co-treatment,and collaborative treatment is likely to become a major focus in future research on dioxin control in sintering processes.

Abstract:Hydrogen energy,recognized as a high-calorific,clean and carbon-free secondary energy source,plays a pivotal role in achieving the"dual-carbon goal".TiFe alloys,with their remarkable hydrogen storage capacity,cost-effectiveness,and mild conditions for hydrogen absorption and desorption,present a promising solution to the challenges of high costs and safety concerns in hydrogen storage and transportation technologies.However,the pronounced oxygen sensitivity of TiFe alloys renders them highly susceptible to oxygen poisoning,leading to the formation of a dense passivation layer on the alloy surface.Despite extensive research indicating that co-doping TiFe alloys with Cu and other elements can enhance the alloy's activation properties,the mechanism by which Cu affects their hydrogen storage properties remains unclear.In this study,we systematically investigate,using density functional theory(DFT)calculations,the role of Cu in modulating the formation of the surface oxide layer on TiFe alloys,and its impact on the hydrogen storage process when Cu substitutes Fe.The results demonstrate that Ti atoms exhibit a strong oxygen affinity,and during the oxidation process,they preferentially form dense titanium oxides.Upon Cu substitution,the continuity of the oxide layer on the alloy surface is significantly reduced,which leads to a decrease in titanium oxide content.Ab initio molecular dynamics(AIMD)simulations reveal that Cu significantly reduces the motion velocity of Ti atoms along the z-axis(from 0.368 Å/ps to 0.182 Å/ps at 150 fs in the forward direction),while the motion velocity of Fe atoms around Cu is notably accelerated,increasing the likelihood of the formation of less dense Fe oxides.These findings suggest that Cu can effectively inhibit the growth of the oxide layer and mitigate its densification.Furthermore,at the microscopic level,Cu can enhance H2 adsorption by lowering the adsorption energy from-2.93 eV to-3.13 eV,and decrease the dissociation energy barrier.Additionally,Cu optimizes the H atom diffusion channel on the surface,reducing the diffusion energy barrier by 64％,thereby enhancing the hydrogen absorption process in TiFe alloys.To validate the theoretical predictions,TiFe and TiFe0.9Cu0.1 alloys were synthesized by the vacuum melting method,and subjected to activation performance and isothermal hydrogen storage tests.Experimental results confirm that Cu reduces the number of activation cycles required for complete activation of TiFe alloys from five to three,significantly enhancing their activation characteristics.Notably,neither the maximum hydrogen storage capacity nor the hydrogen absorption kinetics of the alloys decreased under these conditions,which is consistent with the theoretical calculations.

Abstract:This review focuses on the catalytic hydrogenation of furfural(FFA),a biomass-derived platform chemical,to produce cyclopentanone(CPO)—a high-value industrial compound.The primary objective is to systematically analyze recent progress in catalyst design,reaction mechanisms,and process optimization to overcome the limitations of conventional CPO production methods reliant on fossil resources.The scope encompasses the evaluation of catalytic systems to enhance selectivity,stability,and cost-effectiveness in FFA conversion.Catalysts are classified into noble metals(Pd,Pt,Ru,Au)and non-noble metals(Cu,Ni,Co),with emphasis on their structural and electronic properties.Key strategies include metal-support interface engineering,Lewis/Brønsted acid site modulation,and bimetallic synergism.The reaction mechanism involves the following sequential steps:(1)FFA adsorption and selective C=O hydrogenation to furfuryl alcohol(FA);(2)acid-catalyzed ring-opening and rearrangement to 2-cyclopentenone(2-CPEO);and(3)2-CPEO hydrogenation to CPO.Critical parameters such as temperature(110-180 ℃),H2 pressure(1-5 MPa),and aqueous-phase conditions are discussed.Noble metal catalysts,particularly Pd-based systems,demonstrate exceptional performance.For instance,Pd/NiMoO4 achieves 96.6％CPO yield at 150 ℃ and 4 MPa H2,while Pd/La2Ti2O7 attains 98％yield under similar conditions.Bimetallic catalysts(e.g.,Pd-Cu/C)and variants supported on metal-organic frameworks(MOFs)(e.g.,Pd@Fe-MIL-101)enhance stability and recyclability.Non-noble catalysts,such as Cu/ZrO2(85.3％yield)and Ni/SiC-CrCl3(88.1％yield),exhibit competitive performance through synergistic metal-acid interactions.Reaction parameters critically influence selectivity:aqueous solvents could suppress side reactions(e.g.,tetrahydrofurfuryl alcohol(THFA)formation),while optimal temperatures(140-150 ℃)help balance hydrolysis and hydrogenation kinetics.The review highlights the potential of FFA-to-CPO conversion as a sustainable alternative to fossil-based routes.Noble metal catalysts excel in activity but face economic constraints,whereas non-noble systems(Cu,Ni)offer cost advantages with tunable selectivity.Key challenges include catalyst deactivation and harsh rection conditions.Future efforts should prioritize(1)improving the stability of non-noble catalysts via alloying and defect engineering;(2)integrating continuous-flow reactors with in situ product separation;and(3)exploring liquid hydrogen donors(e.g.,alcohols)to reduce H2 pressure dependence.The mechanistic role of FFA adsorption geometry(vertical vs.horizontal binding)on catalytic selectivity provides a foundational framework for rational catalyst design.Furthermore,the synergy between metallic sites and acidic carriers(e.g.,MOFs,zeolites)in stabilizing reaction intermediates offers novel pathways for enhancing CPO yield.These insights advance biomass valorization and support broader applications in green chemistry and renewable energy sectors.

Abstract:The steel industry is a major source of carbon emissions among global industrial sectors.Driven by the objective of carbon capture,utilization,and storage(CCUS),researchers and industry stakeholder are developing technologies that are emerging as key solutions,facilitating the transition from traditional blast furnace-basic oxygen furnace(BF-BOF)processes to emerging hydrogen-based metallurgy technologies.This paper provides an overview of the current state of crude steel production and its associated carbon emissions.It also discusses their characteristics in the steel industry.Common carbon capture technologies employed in steel plants,including liquid absorption,solid adsorption,and membrane separation methods,are systematically reviewed and evaluated based on their principles,benefits,and drawbacks.Additionally,research progress and representative applications of carbon capture technologies in the global steel industry are summarized.Steel companies and academic institutions are actively developing carbon capture processes tailored to the industry's needs,including chemical absorption and physical adsorption for blast furnace gas treatment.International demonstration projects reveal that conventional technologies,such as monoethanolamine(MEA)absorption,can achieve a CO2 capture rate of 90％,but these technologies require high regeneration energy consumption of 4-5 GJ/t CO2.In contrast,ammonium hydroxide absorption processes can reduce energy consumption to 1.5 GJ/t CO2.The Japanese COURSE50 project has achieved a 30％reduction in CO2 emissions per ton of crude steel,while BaYi Iron & Steel has upgraded its molten reduction ironmaking furnace to a European smelting furnace,attaining a CO2 capture rate of over 97％.However,the global average cost of CO2 capture remains high.Current challenges include:(1)increased energy consumption(2.5-4.0 GJ per ton of steel);(2)infrastructure limitations,as 80％of steel plants lack CO2 pipeline networks;and(3)insufficient carbon pricing coverage,accounting for only 30％-40％of the capture costs.In the future,technological advancements in novel phase-change absorbents(e.g.,eutectic solvents)and metal-organic framework(MOF)adsorption materials are expected to significantly reduce capture costs by 2030 and beyond.This process requires overcoming challenges associated with the collaborative integration of steel plants,chemical industrial parks,and storage sites.For instance,the"hydrogen-carbon co-production"model,a collaboration between HBIS Group and Shell,utilizes captured CO2 for microalgae cultivation and enhanced oil recovery(EOR),thereby establishing a carbon-negative value chain.With the advancement of global carbon neutrality initiatives,the industrialization of CCUS in the steel sector must rely on policy-driven initiatives and collaborative innovation across the value chain(e.g.,hydrogen-carbon co-production models).This review offers a theoretical foundation and practical insights to guide the development of economically viable CCUS pathways,accelerating the steel industry's transition towards carbon neutrality.

Abstract:The excessive emission of carbon monoxide(CO)from steel sintering flue gas poses a significant threat to regional air quality and human health.This necessitates the development of effective CO treatment technologies for sintering flue gas.Among these,catalytic oxidation technology has emerged as a stable and efficient method for CO removal.Noble metal-loaded catalysts,including those based on platinum(Pt),palladium(Pd),gold(Au),ruthenium(Ru),and iridium(Ir),are considered to have significant application potential due to their excellent low-temperature oxidation performance and resistance to water and sulfur.However,challenges arise from the scarcity and high cost of noble metals,as well as the complex composition of flue gases.These factors complicate the application of noble metal-loaded catalysts in industrial settings,highlighting the importance of research focused on CO oxidation.The activity of noble catalysts is primarily influenced by their physicochemical properties,including morphology,particle size,elemental doping,support type,oxygen vacancies,and surface hydroxyl groups.It has been observed that a moderate amount of H2O can enhance CO oxidation on these catalysts,while excessive H2O can inhibit the reaction due to competitive adsorption effects.Additionally,the presence of SO2 in the flue gas can lead to its adsorption on noble metal active sites or the support,further diminishing the adsorption efficiency of CO and O2 and causing carrier sulfation.The CO oxidation reaction on noble metal-loaded catalysts is governed by three mechanisms:Langmuir-Hinshelwood(L-H),Mars-van Krevelen(MvK),and Eley-Rideal(ER).H2O plays a dual role in these pathways,enhancing CO catalytic oxidation in some cases while inhibiting it in others.However,the presence of SO2 typically reduces the adsorption performance of CO and O2,which can lead to decreased catalyst activity or even deactivation.Given the emission characteristics of sintering flue gas,future research on noble metal-supported catalysts should focus on three aspects.(1)Improving stability and anti-poisoning performance:Even after desulfurization,sintering flue gas contains residual SO2,necessitating catalysts that can withstand such conditions;(2)Investigating activity in complex pollutant environments:Research should explore the activity of noble metal-based catalysts in the presence of various pollutants,including SO2,heavy metals,alkali metal dust,and chlorine-containing VOCs;(3)Reducing noble metal loading:Given the high flow rates of sintering flue gas,it is crucial to develop strategies that minimize noble metal usage while maintaining effective CO treatment.This paper aims to provide guidance for the development and optimization design of CO noble metal supported catalysts for sintering flue gas.

Abstract:Hydrogen production via ammonia decomposition faces challenges due to low NH3 conversion,and the activity of ammonia decomposition catalysts requires improvement.Molecular sieves,with their large specific surface areas and well-developed pore structures,can serve as excellent carriers for ammonia decomposition catalysts to enhance their activity.However,the influence of molecular sieve carrier properties on ammonia decomposition remains unclear.Therefore,three types of molecular sieve carriers widely used in ammonia decomposition,namely ZSM-5,SBA-15,and MCM-41,were selected,and a series of Co-based molecular sieve catalysts were prepared by the equal-volume impregnation method.This work investigated the effect of Co-based catalysts with different molecular sieve carriers(ZSM-5,SBA-15,MCM-41)on hydrogen production from ammonia decomposition.The catalytic activity of the Co-based molecular sieve catalysts followed the order:Co/SBA-15＞Co/MCM-41＞Co/ZSM-5.Co/SBA-15 exhibited the best ammonia decomposition activity.The physicochemical properties of the Co-based catalysts were analyzed using characterization techniques including BET,XRD,SEM,H2-TPR,and NH3-TPD to reveal the changes in the molecular sieve carriers before and after loading and their effects on ammonia decomposition performance.The specific surface area,pore structure,surface morphology,catalyst particle size,and acidic sites were found to significantly influence the ammonia decomposition activity.In contrast,the redox capacity of the carriers and the metal grain size had a lesser impact.Based on the catalytic activity and characterization results,we concluded that an ideal carrier for an ammonia decomposition catalyst should possess a high specific surface area,a well-developed pore structure with an appropriate pore size,and a low density of weak acidic sites.The active sites of the ammonia decomposition reaction were associated with the metallic cobalt state,and H2 reduction treatment of the catalyst prior to the reaction could increase the number of active sites,thereby effectively improving its ammonia decomposition activity.Meanwhile,the Co/SBA-15 catalyst exhibited a lower apparent activation energy for ammonia decomposition compared to the other two catalysts.Additionally,the Co/SBA-15 catalyst exhibited excellent catalytic stability and reproducibility.Finally,in situ DRIFTS experiments on the Co/SBA-15 catalyst revealed the enrichment of—NH and—NH2 intermediates on its surface,indicating that the rate-limiting step in the ammonia decomposition reaction might be the recombinative desorption of adsorbed N atoms.This study elucidates how the physicochemical properties of catalyst carriers influence ammonia decomposition performance and provides theoretical guidance for selecting catalyst carriers for this reaction.

Abstract:The reduction of nitrogen oxides(NOx)in industrial flue gas is crucial for achieving coordinated control of fine particulate matter(PM2.5)and ozone(O3)in China's atmosphere.The most common NOx removal method for stationary sources is selective catalytic reduction(SCR)technology using NH3 as a reducing agent,referred to as NH3-SCR.However,the negative effects associated with NH3 introduction,such as secondary pollution caused by NH3 slip and higher carbon emissions,have gradually attracted widespread attention in recent years.This article provides a review and outlook on the research status and application prospects of selective catalytic reduction technology using carbon monoxide(CO)as a reducing agent(CO-SCR).Research has shown that developing high-performance catalysts is the key challenge for CO-SCR technology.CO-SCR catalysts can be broadly categorized into two types:transition metal oxides and supported noble metal materials.Typical catalysts,including Cu-,Co-,Mn-,and Ir-based catalysts,are reviewed in this article.The microscopic reaction process of CO-SCR involves three main steps:(1)the adsorption of reactant molecules,(2)the conversion of intermediate molecules,and(3)desorption and diffusion of product molecules.Among these steps,the preferential adsorption of NO molecules on the active site,followed by dissociation,is the rate-determining step.The interaction between NO and the substrate strongly depends on the surface state and tends to occur at oxygen vacancies on transition metal oxides,while it occurs at unsaturated coordination cation centers on supported noble metal materials.In addition,the impact of CO/NO,oxygen(O2),sulfur dioxide(SO2),and water vapor(H2O)on CO-SCR performance has also been discussed in detail.For example,on the surface of Ir-based catalysts,Ir0(serving as the main active site)is unlikely to remain unchanged throughout the entire reaction process.It is anticipated that Ir0 will be converted to oxidized Irδ+after donating electrons to the antibonding π*orbital of the NO molecule.If new electrons are not replenished promptly,the catalytic activity will gradually decrease as oxidized Irδ+becomes the predominant species,which is the primary reason for the poor stability of the catalyst in the presence of O2.Interestingly,SO2 stabilizes the catalyst and facilitates the generation of Ir0 sites under O2-containing conditions.Therefore,future research should prioritize the development of catalysts tailored to specific applications,and refine the CO-SCR reaction model under diverse conditions,with a focus on synergistic technologies such as the selective circulation coupling of CO-SCR in steel sintering flue gas.Furthermore,the high cost of catalysts remains a crucial obstacle hindering the widespread adoption of CO-SCR technology.

Abstract:Non-ferrous smelter flue gas is a major anthropogenic source of arsenic emissions in China.Because the composition of non-ferrous smelter flue gas is complicated,efficient removal of gaseous arsenic remains a significant challenge.Biomass charcoal usually contains abundant functional groups on its surface,which have a strong affinity for arsenic.Therefore,a modified biomass charcoal adsorbent was synthesized by a hydrothermal method from Camellia oleifera shells.The analysis and characterization results of the adsorbent confirmed that the prepared biomass charcoal had a porous and spherical structure with a large specific surface area(532.441 m2/g)and a well-developed microporous structure(0.647 cm3/g).FTIR confirmed that the prepared biomass charcoal contained a large number of oxygen-containing functional groups such as C—O and C＝O.Gaseous arsenic adsorption experiments revealed that the optimal adsorption temperature of the biomass charcoal for arsenic was 400 ℃,and its maximum arsenic adsorption capacity reached 16.14 mg/g,which was superior to that of traditional mineral adsorbents.The adsorption capacity of biomass charcoal adsorbent at the concentrations of 8 g/kg SO2,10 g/kg HCl,and 16％CO2 maintained an adsorption capacity above 10 mg/g,demonstrating a strong resistance to acid gas poisoning.Furthermore,the presence of O2 in smelting flue gas enhances arsenic removal,whereas H2O has a slight inhibitory effect.The final arsenic adsorption product was characterized using X-ray photoelectron spectroscopy(XPS)and inductively coupled plasma-high performance liquid chromatography(ICP-HPLC).The dominant arsenic species in the adsorption product was As5+,which accounted for 62.7％ of total arsenic at 250 ℃ and under a pure N2 atmosphere.Upon increasing the adsorption temperature to 400 ℃ and O2 volume concentration to 6％,the proportion of As5+increased to almost 100％,indicating that arsenic oxidation plays a crucial role in arsenic removal.The proposed arsenic removal mechanism involves the physical adsorption of gaseous arsenic trioxide on the biomass charcoal surface,followed by oxidation to stable diarsenic pentoxide by the oxygen-containing functional groups,ultimately leading to arsenic purification.The spent biomass charcoal was regenerated by alkaline boiling.After 10 regeneration cycles,the arsenic removal efficiency of biomass charcoal decreased by only 30％,demonstrating that the biomass charcoal from Camellia oleifera shells exhibited good regeneration potential.These results demonstrate the excellent industrial application potential of the biomass charcoal for arsenic pollution control.

Abstract:CF4(tetrafluoromethane),a perfluorinated compound with high thermal stability and global warming potential,poses significant challenges for the conventional catalytic decomposition route due to its robust C—F bonds and chemical inertness.Current thermal catalytic technologies,primarily using aluminum-based catalysts,have demonstrated efficient CF4 decomposition but require reaction temperatures exceeding 600 ℃,which is far beyond the maximum temperature of flue gas from actual aluminum electrolysis(140 ℃).Consequently,there is an urgent need to develop low-temperature CF4 catalytic decomposition technologies to reduce greenhouse gas emissions from the aluminum electrolysis industry.To address this challenge,researchers have proposed the strategy of coupling aluminum-based catalysts with low-temperature plasma.Notably,the hydroxyl-enriched mesoporous aluminum catalyst exhibits remarkable CF4 decomposition efficiency even at room temperature(25 ℃).The key to this breakthrough lies in the formation of hydroxyl sites on the aluminum surface.Hydroxyl-enriched mesoporous aluminum has been successfully prepared through the sol-gel method using aluminum isopropoxide as the aluminum source,which significantly enhances CF4 decomposition efficiency.Experimental results show that,under the reaction conditions of 10％ CF4 concentration and 10 mL/min flow rate,the highest decomposition efficiency of CF4 can reach 95％ using a mesoporous aluminum catalyst coupled with plasma.Even at a flow rate of 50 mL/min,the decomposition rates can still reach 70％.These findings underscore the potential of this new catalyst in practical applications.Compared to commercial alumina,mesoporous aluminum demonstrates superior properties.Specifically,the strong acidic sites and hydroxyl content of mesoporous aluminum are 16.2％ and 118.0％higher,respectively.The surface of mesoporous aluminum contains higher densities of acidic and basic sites,with the weak basic sites being Al—OH and strong basic sites being active oxygen species such as O2-.During the CF4 decomposition reaction,the Al—OH groups on the surface of mesoporous aluminum participate in the decomposition process,transforming CF4 into carbon(C)and aluminum fluoride(AlF3).These products deposit on the catalyst surface,leading to pore blockage and a subsequent decrease in CF4 decomposition efficiency after prolonged reaction.The hydroxyl group plays a pivotal role in CF4 decomposition by serving as a proton donor and an active site.Its dual functionality as a Brønsted acid and a base enhances the overall performance of CF4 decomposition.The presence of hydroxyl groups facilitates the breakdown of CF4 and improves the catalyst's stability and longevity,making it a promising solution for reducing greenhouse gas emissions from aluminum electrolysis processes in industrial applications.

Abstract:The presence of chlorine(Cl)in biomass or pulverized coal poses a significant challenge in chemical looping combustion(CLC),as it can corrode both oxygen carriers and the boiler's heat exchange equipment.Despite this,there is a notable lack of research focused on hydrochloric acid(HCl)in CLC processes.This study explores the development of a composite oxygen carrier aimed at enhancing chlorine fixation and corrosion resistance.To achieve this,two adsorbents,Ca-based and Ba-based,were selected.The composite oxygen carrier was synthesized using the sol-gel method,and a batch fluidized bed served as the experimental setup for biomass CLC experiments.The study investigated the effects of Ca and Ba doping on the combustion characteristics and chlorine bonding of Cu-based oxygen carriers.The results indicate that alkaline earth metals in Ca-Cu and Ba-Cu formulations preferentially form stable chlorides with HCl,enhancing the lattice oxygen activity of the carriers and promoting gas-solid reactions for chlorine capture.Notably,the peak CO2 production and peak height for Ca-Cu and Ba-Cu carriers were significantly higher than those for standard Cu oxygen carriers.Additionally,Ca/Ba doping improved the gasification of biomass coke,with no detectable levels of H2 and CH4 during the reduction stage,suggesting more complete conversion of these gases by oxygen carriers.The peak CO concentrations were measured at 0.08％,0.07％,and 0.06％ for Ca-Cu,Ba-Cu,and Cu carriers,indicating enhanced CO conversion efficiency.Further experiments assessed the impact of temperature and oxygen-fuel ratio on combustion and dechlorination performance.Increasing the temperature from 800 ℃ to 900 ℃ resulted in a combustion efficiency rise for the Cu oxygen carrier from 87.0％±0.5％to 94.7％±0.4％,representing a maximum increase of 8.6％.Conversely,the combustion efficiency of the Ca oxygen carrier decreased slightly from 95.6％±0.6％to 95.2％±0.1％.In contrast,the Ba oxygen carrier showed a significant improvement,increasing from 88.0％±1.6％ to 94.7％±0.4％,with a maximum increase of 8.7％.In biomass CLC,Ca-Cu oxygen carriers demonstrated superior temperature stability,while the combustion efficiency of Ba-Cu carriers was significantly affected by temperature changes.When the oxygen-fuel ratio was raised from 1.5 to 2.0,the chlorine fixation efficiency for Cu carriers increased from 84.3％±6.3％to 96.3％±1.2％.Both Ca-and Ba-based oxygen carriers maintained 100％ chlorine fixation efficiency,suggesting that lower oxygen-fuel ratios could be utilized in biomass dechlorination processes,thereby reducing carbon capture operating costs.Moreover,doping with Ca and Ba increased the specific surface area and pore volume of the oxygen carriers,increasing the contact area with biomass and thereby stabilizing their performance in CLC.This study helps to understand the chlorine fixation characteristics of alkaline earth metals,promoting the development and application of chlorine-resistant carriers.

Abstract:High-temperature incineration is the predominant method for managing municipal solid waste,enabling effective heat and heavy metal recovery and facilitating efficient energy and resource recycling.Fly ash generated from municipal solid waste incineration contains various heavy metals,chloride salts,dioxins,and other harmful substances,seriously impacting the ecological environment and human health.Vacuum melting treatment of fly ash effectively eliminates heavy metals and chloride salts,rapidly decomposes dioxins,and significantly reduces fly ash toxicity.This study optimized the temperature,vacuum level,and holding time for vacuum melting treatment,identifying the optimal conditions of 1 400℃,100 Pa,and 3.0 hours.The total chlorine removal efficiency reached 92.00％,and the soluble chlorine removal efficiency reached 96.85％.XRD phase analysis revealed that NaCl and KCl disappeared,while crystalline phases of Ca,Si,and Al minerals appeared under optimal conditions.The removal rates of various heavy metals increased significantly,with removal efficiencies of 81.34％,89.26％,90.86％,and 88.00％for Cu,Zn,Pb,and Cd,respectively.SEM imaging of fly ash treated under optimal conditions showed a uniform and smooth surface,indicating a transformation to a molten glass state.The DTPA method was used to assess the heavy metal toxicity.Results showed that the concentrations of Cu,Zn,Mn,and Ba in the treated samples were 48.51,92.41,51.93,and 48.52 mg/kg,respectively.The toxicity of heavy metals(as measured by EDTA extraction)decreased significantly compared to the original fly ash,although some ecological risks remain.After vacuum melting treatment,dioxin content and toxic equivalents were significantly reduced,with an overall emission reduction exceeding 96％.This study provides crucial insights for the vacuum melting disposal of fly ash,offering technical parameters and practical guidance for its safe disposal and resource utilization.However,this study only examined the phase characteristics of fly ash but lacked a comprehensive analysis of pollutant migration and transformation mechanisms.Further research should focus on the efficient resource utilization of the post-melting slag and investigate the mechanisms and kinetics of pollutant migration and transformation to develop more effective control strategies and technologies.