Removal of Chromium from Chromium（VI） Solutions by Adsorption and Reduction Using Immobilized Persimmon Gel

The removal of chromium（Vl） from an aqueous solution using persimmon gel was examined. The amount of chromium（VI） removed was strongly affected by the pH of the solution, with all ehromium（VI） being removed at pH 2 or lower. However, in a solution containing, 15 mg dry weight of immobilized persimmon gel, the amount of removed chromium（VI） decreased as the pH increased. A part of chromium（VI） was reduced another oxidation stage, mainly chromium（III）, by immobilized persimmon gel. The amount of reduced chromium（III） in the solution was increased with decreasing the pH of the solution. As a result, the amount of total chromium removed was maximal at pH 2. The amount of chromium removed were affected by the chromium concentration and the amount of gel. The maximal amount of chromium removed by the column system was also discussed.

In-situ self-templated preparation of porous core-shell Fe_(1-x)S@N,S co-doped carbon architecture for highly efficient oxygen reduction reaction

Transition metal compound(TMC)/carbon hybrids,as prospering electrocatalyst,have attracted great attention in the field of oxygen reduction reaction(ORR).Their morphology,structure and composition often play a crucial role in determining the ORR performance.In this work,we for the first time report the successful fabrication of porous core-shell Fe_(1-x)S@N,S co-doped carbon(Fe_(1-x)S@NSC-t,t represents etching time)by a novel in-situ self-template induced strategy using Fe3O4 nanospheres and pyrrole as sacrificial self-template.The post-polymerization of pyrrole can be accomplished by the Fe^(3+)released through the etching of Fe_(3)O_(4) by HCl acid.Thus,the etching time has a significant effect on the morphology,structure,composition a nd ORR performance of Fe_(1-x)S@NSC-t.Based on the cha racterizations,we find Fe_(1-x)S@NSC-24 can realize effective and balanced combination of Fe_(1-x)S and NSC,possessing porous core-shell architecture,optimized structure defect,specific surface area and doped heteroatoms configurations(especially for pyridinic N,graphitic N and Fe-N structure).These features thus lead to outstanding catalytic activity and cycling stability towards ORR.Our work provides a good guidance on the design of TMC/carbon-based electrodes with unique stable morphology and optimized structure and composition.

Preparation of Phenolic Resin/Silver Nanocomposites via in-situ Reduction

Resol type phenolic resin/silver nanocomposite was prepared by in-situ reduction method, in which the curing of phenolic resin and the formation of silver nano-particles took place simultaneously. The silver ions were reduced completely to silver nanoparticles, which were dispersed homogeneously in the resin matrix with narrow size distribution.

Evaluation of In-situ Sludge Reduction and Enhanced Nutrient Removal in an Integrated Repeatedly Coupling Aerobic and Anaerobic and Oxic-setting-anaerobic System

Aiming to achieve simultaneous good performances of in-situ sludge reduction and effluent quality,an integrated repeatedly coupling aerobic and anaerobic and oxic-setting-anaerobic system( r CAA + OSA) is developed to reduce sludge production and enhance nutrient removal. Considering the mechanism of in-situ sludge reduction in this r CAA +OSA system,the combined effect of energy uncoupling metabolism and sludge cryptic growth maybe attributed to the higher reduction of biomass. Results show that the maximal sludge reduction in this r CAA + OSA system is obtained when the hydraulic retention time( HRT) is controlled at6. 5 h,which an increase in 16. 67% reduction in excess sludge is achieved compared with OSA system( HRT of 6. 5 h). When compared the performances of effluent qualities,the enhanced nutrient removal efficiencies also can be observed in this r CAA + OSA system. Three-dimensional excitation emission matrix( 3D-EEM)fluorescence spectroscopy is applied to characterize the effluent organic matters( Ef OM) under different HRTs in the OSA and the r CAA+OSA systems. Analyses of 3D-EEM spectra show that more refractory humic-like and fulvic-like components are observed in the effluent of the OSA system. On the basis of these results,simultaneous enhanced in-situ sludge reduction and improved nutrient removal can be obtained in the r CAA +OSA systems.

Electrocatalysts with atomic-level site for nitrate reduction to ammonia

Ammonia(NH_(3))is an important raw material for modern agriculture and industry,being widely demanded to sustain the sustainable development of modern society.Currently,the industrial production methods of NH_(3),such as the traditional Haber-Bosch process,have drawbacks including high energy consumption and significant carbon dioxide emissions.In recent years,the electrocatalytic nitrate reduction reaction(NO_(3)RR)powered by intermittent renewable energy sources has gradually become a multidisciplinary research hotspot,as it allows for the efficient synthesis of NH_(3)under mild conditions.In this review,we focus on the research of electrocatalysts with atomic-level site,which have attracted attention due to their extremely high atomic utilization efficiency and unique structural characteristics in the field of NO_(3)RR.Firstly,we introduce the mechanism of nitrate reduction for ammonia synthesis and discuss the in-situ characterization techniques related to the mechanism study.Secondly,we review the progress of the electrocatalysts with atomic-level site for nitrate reduction and explore the structure-activity relationship to guide the rational design of efficient catalysts.Lastly,the conclusions of this review and the challenges and prospective of this promising field are presented.

Reductive immobilization and long-term remobilization of radioactive pertechnetate using bio-macromolecules stabilized zero valent iron nanoparticles

Reductive immobilization of radioactive pertechnetate(99TcO4^-) in simulated groundwater was studied by prepared carboxymethyl cellulose(CMC) and starch stabilized zero valent iron nanoparticles(nZVI),and long-term remobilization of reduced Tc was also evaluated under anoxic and oxic conditions.The stabilized nZVI can effectively reduce soluble 99Tc(Ⅶ) to insoluble 99 Tc(Ⅳ),and they can be easily delivered into a contaminated groundwater zone and facilitate in situ remediation.In this study,CMCstabilized nZVI showed higher reactivity than that using starch as the stabilizer.Batch experiments indicated that more than 99% of 99 Tc(Ⅶ)(CO=12 mg/mL) was reduced and removed from groundwater by CMC-stabilized nZVI with a CMC content of 0.2%(w/w) at a broad pH of 5-8.X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS) analyses further confirmed that 99Tc(Ⅶ)O4^-transformed into 99Tc(Ⅳ)O2(s).The presence of bicarbonate exhibited insignificant effect on Tc immobilization,while humic acid(HA) inhibited reaction mainly due to retardation on electron transfer and formation of Tc(IV)-HA complexes.More interesting,the immobilized Tc(Ⅳ) remained insoluble even after 120 d under anoxic condition,while only^21 % was remobilized when exposed to air.Therefore,biomacromolecules stabilized nZVI nanoparticles could be a viable alternative for in situ remediation of radioactive contamination in groundwater.

Propane dehydrogenation catalyzed by in-situ partially reduced zinc cations confined in zeolites

Propane dehydrogenation(PDH), employing Pt-or Cr-based catalysts, represents an emerging industrial route for propylene production. Due to the scarcity of platinum and the toxicity of chromium, alternative PDH catalysts are being pursued. Herein, we report the construction of Zn-containing zeolite catalysts,namely Zn@S-1, for PDH reaction. Well-isolated zinc cations are successfully trapped and stabilized by the Si-OH groups in S-1 zeolites via in-situ hydrothermal synthesis. The as-prepared Zn@S-1 catalysts exhibit good dehydrogenation activity, high propylene selectivity, and regeneration capability in PDH reaction under employed conditions. The in-situ partial reduction of zinc species is observed and the partially reduced zinc cations are definitely identified as the active sites for PDH reaction.

Sulphur-doped ordered mesoporous carbon with enhanced electrocatalytic activity for the oxygen reduction reaction

Metal-free, heteroatom functionalized carbon-based catalysts have made remarkable progress in recent years in a wide range of applications related to energy storage and energy generation. In this study, high surface area mesoporous ordered sulphur doped carbon materials are obtained via one-pot hydrothermal synthesis of carbon/SBA-15 composite after removal of in-situ synthesized hard template SiO2. 2-thiophenecarboxy acid as sulphur source gives rise to sulphur doping level of 5.5 wt%. Comparing with pristine carbon, the sulphur doped mesoporous ordered carbon demonstrates improved electro-catalytic activity in the oxygen reduction reaction in alkaline solution. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Synthesis, in-situ coating and characterization of scorodite with high leaching stability

To improve stability of scorodite,a method of simultaneous synthesis and in-situ coating of scorodite was proposed.Scorodite particles with polyhedral and raspberry-like morphologies were synthesized in an Fe(Ⅱ).As(Ⅴ).H2O system at 90℃and pH 1.5 by blowing oxygen gas into the system.When the initial Fe/As molar ratio exceeded 1:1,a coating of sulfate-containing iron(hydr)oxides formed on the surfaces of scorodite particles during synthesis.To evaluate the leaching stability of synthesized scorodite samples,toxicity characteristic leaching procedure(TCLP)tests were conducted at pH 4.93 for 60 h,and long-term leaching tests were conducted for 30.40 d within a pH range of 5.40.10.88.The leaching results indicated that the release of arsenic from scorodite was noticeably postponed by the coating,and the average arsenic concentrations in the leaching solutions were as low as 0.12 mg/L in the TCLP tests and lower than 0.5 mg/L in the long-term leaching tests.

A Review of In‑Situ Techniques for Probing Active Sites and Mechanisms of Electrocatalytic Oxygen Reduction Reactions

Electrocatalytic oxygen reduction reaction(ORR)is one of the most important reactions in electrochemical energy technologies such as fuel cells and metal–O2/air batteries,etc.However,the essential catalysts to overcome its slow reaction kinetic always undergo a complex dynamic evolution in the actual catalytic process,and the concomitant intermediates and catalytic products also occur continuous conversion and reconstruction.This makes them difficult to be accurately captured,making the identification of ORR active sites and the elucidation of ORR mechanisms difficult.Thus,it is necessary to use extensive in-situ characterization techniques to proceed the real-time monitoring of the catalyst structure and the evolution state of intermediates and products during ORR.This work reviews the major advances in the use of various in-situ techniques to characterize the catalytic processes of various catalysts.Specifically,the catalyst structure evolutions revealed directly by in-situ techniques are systematically summarized,such as phase,valence,electronic transfer,coordination,and spin states varies.In-situ revelation of intermediate adsorption/desorption behavior,and the real-time monitoring of the product nucleation,growth,and reconstruction evolution are equally emphasized in the discussion.Other interference factors,as well as in-situ signal assignment with the aid of theoretical calculations,are also covered.Finally,some major challenges and prospects of in-situ techniques for future catalysts research in the ORR process are proposed.

Mechanistic insight into N_2O formation during NO reduction by NH_3 over Pd/CeO_2 catalyst in the absence of O_2

N2O is a major by-product emitted during low-temperature selective catalytic reduction of NO with NH3(NH3-SCR), which causes a series of serious environmental problems. A full understanding of the N2O formation mechanism is essential to suppress the N2O emission during the low-temperature NH3-SCR, and requires an intensive study of this heterogeneous catalysis process. In this study, we investigated the reaction between NH3 and NO over a Pd/CeO2 catalyst in the absence of O2, using X-ray photoelectron spectroscopy, NH3-temperature-programmed desorption, NO-temperature-programmed desorption, and in-situ Fourier-transform infrared spectroscopy. Our results indicate that the N2O formation mechanism is reaction-temperature-dependent. At temperatures below 250 ℃, the dissociation of HON, which is produced from the reaction between surface H· adatoms and adsorbed NO, is the key process for N2O formation. At temperatures above 250 ℃,the reaction between NO and surface N·, which is produced by NO dissociation, is the only route for N2O formation, and the dissociation of NO is the rate-determining step. Under optimal reaction conditions, a high performance with nearly 100% NO conversion and 100% N2 selectivity could be achieved. These results provide important information to clarify the mechanism of N2O formation and possible suppression of N2 O emission during low-temperature NH3-SCR.

Slope analysis based on local strength reduction method and variable-modulus elasto-plastic model

Employing an ideal elasto-plastic model,the typically used strength reduction method reduced the strength of all soil elements of a slope.Therefore,this method was called the global strength reduction method(GSRM).However,the deformation field obtained by GSRM could not reflect the real deformation of a slope when the slope became unstable.For most slopes,failure occurs once the strength of some regional soil is sufficiently weakened; thus,the local strength reduction method(LSRM)was proposed to analyze slope stability.In contrast with GSRM,LSRM only reduces the strength of local soil,while the strength of other soil remains unchanged.Therefore,deformation by LSRM is more reasonable than that by GSRM.In addition,the accuracy of the slope's deformation depends on the constitutive model to a large degree,and the variable-modulus elasto-plastic model was thus adopted.This constitutive model was an improvement of the Duncan–Chang model,which modified soil's deformation modulus according to stress level,and it thus better reflected the plastic feature of soil.Most importantly,the parameters of the variable-modulus elasto-plastic model could be determined through in-situ tests,and parameters determination by plate loading test and pressuremeter test were introduced.Therefore,it is easy to put this model into practice.Finally,LSRM and the variable-modulus elasto-plastic model were used to analyze Egongdai ancient landslide.Safety factor,deformation field,and optimal reinforcement measures for Egongdai ancient landslide were obtained based on the proposed method.

In-situ reconstruction of catalysts in cathodic electrocatalysis: New insights into active-site structures and working mechanisms

Cathodic electrocatalytic reactions, such as hydrogen evolution and CO_(2)/N_(2) reduction, are the key processes that store intermittent electricity into stable chemical energy. Although a great progress has been made to boost activity and selectivity via elaborative catalyst design, the structure–property relationships have not been sufficiently understood in the context of surface reconfiguration under working conditions. Recent efforts devoted to tracking dynamic evolution of electrocatalysts using in-situ and/or operando techniques gave new insights into the real structure and working mechanism of active sites,and provided principles to design better catalysts. The achievement of cathodic electrocatalysts in this subject is herein summarized, focusing on the correlations between reconstructed surface and electrocatalytic performance. Briefly, the thermodynamics of reconstruction at cathodes is discussed at first, and then the representative progresses in H_(2) evolution and CO_(2)/N_(2) reduction are introduced in sequence to acquire insights into electrochemical processes on in-situ reconfigured surfaces or interfaces. Finally, a perspective is offered to guide future investigations. This review is anticipated to shed some new light on in-depth understanding cathodic electrocatalysis and exploiting prominent electrocatalysts.

Research progress of precise structural regulation of single atom catalyst for accelerating electrocatalytic oxygen reduction reaction

The development and utilization of renewable clean energy can effectively solve the two major problems of energy and environment. As an efficient power generation device that converts hydrogen energy into electric energy, fuel cell has attracted more and more attention. For fuel cells, the oxygen reduction reaction(ORR) at the cathode is the core reaction, and the design and development of high-performance ORR catalysts remain quite challenging. Since the microenvironment of the active center of single atom catalysts(SACs) has an important influence on its catalytic performance, it has been a research focus to improve the ORR activity and stability of electrocatalysts by adjusting the structure of the active center through reasonable structural regulation methods. In this review, we reviewed the preparation and structure–activity relationship of SACs for ORR. Then, the structural precision regulation methods for improving the activity and stability of ORR electrocatalysts are discussed. And the advanced in-situ characterization techniques for revealing the changes of active sites in the electrocatalytic ORR process are summarized. Finally, the challenges and future design directions of SACs for ORR are discussed. This work will provide important reference value for the design and synthesis of SACs with high activity and stability for ORR.

Reductive immobilization of Re(VⅡ)by graphene modified nanoscale zero-valent iron particles using a plasma technique

Technetium-99(~99Tc),largely produced by nuclear fission of ~235U or ~239Pu,is a component of radioactive waste.This study focused on a remediation strategy for the reduction of pertechnetate(Tc O_4^-)by studying its chemical analogue rhenium(Re(VⅡ))to avoid the complication of directly working with radioactive elements.Nanoscale zero-valent iron particles supported on graphene(NZVI/r GOs)from GOs-bound Fe ions were prepared by using a H_2/Ar plasma technique and were applied in the reductive immobilization of perrhenate(Re O_4^-).The experimental results demonstrated that NZVI/r GOs could efficiently remove Re from the aqueous solution,with enhanced reactivity,improved kinetics(50 min to reach equilibrium)and excellent removal capacity(85.77 mg/g).The results of X-ray photoelectron spectroscopy analysis showed that the mechanisms of Re immobilization by NZVI/r GOs included adsorption and reduction,which are significant to the prediction and estimation of the effectiveness of reductive Tc O_4^- by NZVI/r GOs in the natural environment.

Inner-pore reduction nucleation of palladium nanoparticles in highly conductive wurster-type covalent organic frameworks for efficient oxygen reduction electrocatalysis

Covalent organic frameworks(COFs)have emerged as a class of promising supports for electrocatalysis because of their advantages including good crystallinity,highly ordered pores,and structural diversity.However,their poor conductivity represents the main obstruction to their practical application.Here,we reported a novel synthesis strategy for synergistically endowing a triphenylamine-based COFs with improved electrical conductivity and excellent catalytic activity for oxygen reduction,via the in-situ redox deposition and confined growth of palladium nanoparticles inside the porous structure of COFs using reductive triphenylamine frameworks as reducing agent;meanwhile,the triphenylamine unit was oxidized to radical cation structure and affords radical cation COFs with conductivity as high as3.2*10^(-1) S m^(-1).Such a uniform confine palladium nanoparticle on highly conductive COFs makes it an efficient electrocatalyst for four-electron oxygen reduction reaction(4e-ORR),showing excellent activities and fast kinetics with a remarkable half-wave potential(E_(1/2))of 0.865 V and an ultralow Tafel slope of 39.7 mV dec^(-1) in alkaline media even in the absence of extra commercial conductive fillers.The generality of this strategy was proved by preparing the different metal and metal alloy nanoparticles supported on COFs(Au@COF,Pt@COF,AuPd@COF,AgPd@COF,and PtPd@COF)using reductive triphenylamine frameworks as reducing agent.This work not only provides a facile strategy for the fabrication of highly conductive COF supported ORR electrocatalysts,but also sheds new light on the practical application of Zn-air battery.

Reductive immobilization of perrhenate in soil and groundwater using starch-stabilized ZVI nanoparticles

Perrhenate(ReO4-) was used as nonradioactive surrogate for the radionuclide pertechnetate(99TcO-4) to investigate the potential of using starch-stabilized zero valent iron(ZVI) nanoparticles for reductive immobilization of pertechnetate in soil and groundwater.Batch kinetic tests indicated that the starch-stabilized ZVI nanoparticles were able to reductively remove ～96% of perrhenate(10 mg/L) from water within 8 h.XRD analyses confirmed that ReO 2 was the reduction product.A pseudo-first-order kinetic model was able to interpret the kinetic data,which gave a pseudo first order rate constant(kobs) value of 0.43h-1 at pH 6.9 and room temperature(25℃).Increasing solution pH up to 8 progressively increased the reaction rate.However,highly alkaline pH(10) resulted in much inhibited reaction rate.Consequently,the optimal pH range was identified to be from 7 to 8.Increasing solution temperature from 15 to 45℃ increased k obs from 0.38 to 0.53 h-1.The classical Arrhenius equation was able to interpret the temperature effect,which gave a low activation energy value of 7.61 kJ/mol.When the ReO-4-loaded loess was treated with the stabilized nanoparticles suspension([Fe]=560 mg/L),the water leachable ReO-4 was reduced by 57% and nearly all eluted Re was in the form of ReO2.This finding indicates that starch-stabilized ZVI nanoparticles are promising for facilitating in situ immobilization of ReO-4 in soil and groundwater.

Novel high-entropy perovskite-type symmetrical electrode for efficient and durable carbon dioxide reduction reaction

Excessive emission of carbon dioxide(CO_(2))has posed an imminent threat to human's environment and global prosperity.To achieve a sustainable future,solid oxide electrolysis cell(SOEC),which can efficiently combine CO_(2)reduction reaction(CO_(2)RR)and renewable energy storage,has become increasingly attractive owing to its unique functionalities.Additionally,symmetrical SOEC(SSOEC)has been considered as one of the most versatile cell configurations due to its simplified process,high compatibility,and low cost.However,the electrode material requirements become very demanding since efficient catalytic-activities are required for both CO_(2)RR and oxygen evolution reaction(OER).Herein,we demonstrate a novel high-entropy perovskite type symmetrical electrode Pr_(0.5)Ba_(0.5)Mn_(0.2)Fe_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2)O_(3-δ)(HE-PBM)for SSOEC.B-site doping of transition metals such as Mn,Fe,Co,Ni,and Cu in HE-PBM anode has been found to strongly accelerate the OER in the anode.Moreover,the presence of in-situ formed Fe–Co–Ni–Cu quaternary alloy nanocatalysts from HE-PBM cathode under reducing atmosphere has resulted in superior catalytic-activity towards CO_(2)RR.The faster kinetics are also reflected by the significantly low polarization resistance of 0.289Ω⋅cm^(-2)and high electrolysis current density of 1.21 A⋅cm^(-2)for CO_(2)RR at 2.0 V and 800℃.The excellent electrochemical performance and stability demonstrate that the highentropy perovskite material is a promising electrode material in SSOEC for efficient and durable CO_(2)RR.

Zeolite-mediated hybrid Cu^(+)/Cu~0 interface for electrochemical nitrate reduction to ammonia

The electrocatalytic conversion of reactive nitrogen species to ammonia is a promising strategy for efficient NH_(3) synthesis.In this study,we reveal that the hybrid Cu^(+)/Cu~0 interface is catalytically active for electrochemical ammonia synthesis from nitrate reduction.To maintain the hybrid Cu^(+)/Cu~0 state at negative reaction potentials,hydrophilic zeolite is used to modify Cu/Cu_(2)O electrocatalyst,which demonstrates an impressive NH_(3) production rate of 41.65 mg h^(-1) cm^(-2)with ~100% Faradaic efficiency of ammonia synthesis at-0.6 V vs.RHE.In-situ Raman spectroscopy unveil the high activity originates from the zeolite reconstruction at the electrode–electrolyte interface,which protects the valence state of Cu~0/Cu^(+) site under negative potential and promotes electrochemical activity towards NH_(3) synthesis.

Enhancing the electrocatalytic performance of nitrate reduction to ammonia by in-situ nitrogen leaching

Electrochemical nitrate reduction reaction (NITRR) is regarded as a “two birds-one stone” method for the treatment of nitrate contaminant in polluted water and the synthesis of valuable ammonia, which is retarded by the lack of highly reactive and selective electrocatalysts .Herein, for the first time, nickel foam supported Co_(4) N was designed as a high-performance NITRR catalyst by an in-situ nonmetal leaching-induced strategy.At the optimal potential, the Co_(4) N/NF catalyst achieves ultra-high Faraday efficiency and NH_(3) selectivity of 95.4% and 99.4%, respectively.Ex situ X-ray absorption spectroscopy (XAS), together with other experiments powerfully reveal that the nitrogen vacancies produced by nitrogen leaching are stable and play a key role in boosting nitrate reduction to ammonia.Theoretical calculations confirm that Co_(4) N with abundant nitrogen vacancies can optimize the adsorption energies of NO_(3)^(-) and intermediates, lower the free energy (Δ G ) of the potential-determining step (*NH_(3) to NH_(3) ) and inhibit the formation of N-containing byproducts.In addition, we also conclude that the nitrogen vacancies can stabilize the adsorbed hydrogen, making H_(2) quite difficult to produce, and lowering ΔG from *NO to *NOH, which facilitates the selective reduction of nitrate.This study reveals significant insights about the in-situ nonmetal leaching to enhance the NITRR activity.