Thermal pretreatment of willow branches impacts yield and pore development of activated carbon in subsequent activation with ZnCl_(2) via modifying cellulose structure

Development of pore structures of activated carbon(AC)from activation of biomass with ZnCl_(2) relies on content and structure of cellulose/hemicellulose in the feedstock.Thermal pretreatment of biomass could induce dehydration and/or aromatization to change the structure of cellulose/hemicellulose.This might interfere with evolution of structures of AC,which was investigated herein via thermal pretreatment of willow branch(WB)from 200 to 360℃and the subsequent activation with ZnCl_(2) at 550℃.The results showed that thermal pretreatment at 360℃(WB-360)could lead to substantial pyrolysis to form biochar,with a yield of 31.9%,accompanying with nearly complete destruction of cellulose crystals and remarkably enhanced aromatic degree.However,cellulose residual in WB-360 could still be activated to form AC-360 with specific surface area of 1837.9 m~2·g^(-1),which was lower than that in AC from activation of untreated WB(AC-blank,2077.8 m~2·g^(-1)).Nonetheless,the AC-200 from activation of WB-200 had more developed pores(2113.9 m~2·g^(-1))and superior capability for adsorption of phenol,due to increased permeability of ZnCl_(2) to the largely intact cellulose structure in WB-200.The thermal pretreatment did increase diameters of micropores of AC but reduced the overall yield of AC(26.8%for AC-blank versus 18.0%for AC-360),resulting from accelerated cracking but reduced intensity of condensation.In-situ infrared characterization of the activation showed that ZnCl_(2) mainly catalyzed dehydration,dehydrogenation,condensation,and aromatization but not cracking,suppressing the formation of derivatives of cellulose and lignin in bio-oil.The thermal pretreatment formed phenolic-OH and C=O with higher chemical innerness,which changed the reaction network in activation,shifting morphology of fibrous structures in AC-blank to“melting surface”in AC-200 or AC-280.

Effects of elevated CO_2 concentration and nitrogen supply on biomass and active carbon of freshwater marsh after two growing seasons in Sanjiang Plain, Northeast China

An experiments were carried out with treatments differing in nitrogen supply （0, 5 and 15 g N/m^2） and CO2 levels （350 and 700 μmol/mol） using OTC （open top chamber） equipment to investigate the biomass of Calamagrostis angustifolia and soil active carbon contents after two years. The results showed that elevated CO2 concentration increased the biomass of C. angustifolia and the magnitude of response varied with each growth period. Elevated CO2 concentration has increased aboveground biomass by 16.7% and 17.6% during the jointing and heading periods and only 3.5% and 9.4% during dough and maturity periods. The increases in belowground biomass due to CO2 elevation was 26.5%, 34.0% and 28.7% during the heading, dough and maturity periods, respectively. The responses of biomass to enhanced CO2 concentrations are differed in N levels. Both the increase of aboveground biomass and belowground biomass were greater under high level of N supply （15 g N/m^2）. Elevated CO2 concentration also increased the allocation of biomass and carbon in root. Under elevated CO2 concentration, the average values of active carbon tended to increase. The increases of soil active soil contents followed the sequence of microbial biomass carbon （10.6%） 〉 dissolved organic carbon （7.5%） 〉 labile oxidable carbon （6.6%） 〉 carbohydrate carbon （4.1%）. Stepwise regressions indicated there were significant correlations between the soil active carbon contents and plant biomass. Particularly, microbial biomass carbon, labile oxidable carbon and carbohydrate carbon were found to be correlated with belowground biomass, while dissolved organic carbon has correlation with aboveground biomass. Therefore, increased biomass was regarded as the main driving force for the increase in soil active organic carbon under elevated CO2 concentration.

活性炭负载TiO_(2)催化臭氧的造纸废水处理方法研究

造纸废水的处理一直是水利水电工程关注的重点项目。造纸废水中含有大量的污染物质,若是直接排放到环境中,将会对环境造成严重危害。为此,研究一种活性炭负载TiO_(2)催化臭氧的造纸废水处理方法尤为重要。基于此,从水利水电工程废水储蓄池中采集造纸废水水样,配制TiO_(2)催化剂,制备活性炭,将二者混合形成活性炭负载TiO_(2)催化剂;利用催化剂与臭氧充分接触后发生的氧化反应,去除废水中的有机污染物,从而完成造纸废水的处理。测试结果表明:活性炭负载TiO_(2)催化剂对各种污染物质具有很好的去除效果,且催化剂中TiO_(2)负载量越高,催化剂的去除率越高。随着时间的推移,BOD5逐渐降低,水体中的污染物逐渐被分解和消除,证明了所研究方法在造纸废水处理中的应用效果。

Construction of efficient active sites through cyano‐modified graphitic carbon nitride for photocatalytic CO_(2) reduction

The active site amount of photocatalysts,being the key factors in photocatalytic reactions,directly affects the photocatalytic performance of the photocatalyst.Pristine graphitic carbon nitride(g‐C_(3)N_(4))exhibits moderate photocatalytic activity due to insufficient active sites.In this study,cyano‐modified porous g‐C_(3)N_(4)nanosheets(MCN‐0.5)were synthesized through molecular self‐assembly and alkali‐assisted strategies.The cyano group acted as the active site of the photocatalytic reaction,because the good electron‐withdrawing property of the cyano group promoted carrier separation.Benefiting from the effect of the active sites,MCN‐0.5 exhibited significantly enhanced photocatalytic activity for CO2 reduction under visible light irradiation.Notably,the photocatalytic activity of MCN‐0.5 was significantly reduced when the cyano groups were removed by hydrochloric acid(HCl)treatment,further verifying the role of cyano groups as active sites.The photoreduction of Pt nanoparticles provided an intuitive indication that the introduction of cyano groups provided more active sites for the photocatalytic reaction.Furthermore,the controlled experiments showed that g‐C_(3)N_(4)grafted with cyano groups using melamine as the precursor exhibited enhanced photocatalytic activity,which proved the versatility of the strategy for enhancing the activity of g‐C_(3)N_(4)via cyano group modification.In situ diffuse reflectance infrared Fourier transform spectroscopy and theoretical calculations were used to investigate the mechanism of enhanced photocatalytic activity for CO2 reduction by cyano‐modified g‐C_(3)N_(4).This work provides a promising route for promoting efficient solar energy conversion by designing active sites in photocatalysts.

Photocatalytic Characterization of TiO_2 Supported on Active Carbon

The Photocatalytic characterization of TiO2 supported on active carbon was investigated for photocatalytic decomposition of dichloroacetic acid. It was found that TiO2 / AC exhibited a higher photocatalytic activity than pure TiO2. The reason is that active carbon acting as powerful adsorbent supports makes high concentration environments of organic pollutant molecules around TiO2 particles.

Co_(2)N Nanoparticles Anchored on N-Doped Active Carbon as Catalyst for Oxygen Reduction Reaction in Zinc–Air Battery

The development of efficient catalytic electrode toward oxygen reduction reaction(ORR)is still a great challenge for the wide use of zinc–air batteries.Herein,Co_(2)N nanoparticles(NPs)anchored on N-doped carbon from cattail were verified with excellent catalytic performances for ORR.The onset and half-wave potentials over the optimal catalyst reach to 0.96 V and 0.84 V,respectively.Current retention rates of 96.8%after 22-h test and 98.8%after running 1600 s were obtained in 1 M methanol solution.Density functional theory simulation proposes an apparently increased electronic states of Co_(2)N in N-doped carbon layer close to the Fermi level.Higher charge density,favorable adsorption,and charge transfer of intermediates originate from the coexistence of Co_(2)N NPs and N atoms in carbon skeleton.The superior catalytic activity of composites also was confirmed in zinc–air batteries.This novel catalytic property and controllable preparation approach of Co_(2)Ncarbon composites provide a promising avenue to fabricate metal-containing catalytically active carbon from biomass.

Preparation and Supercapacitive Properties of Fe_2O_3/Active Carbon Nanocomposites

Fe2O3/active carbon（Fe2O3/AC） nanocomposites were readily fabricated by pyrolyzing Fe3＋ impregnated active carbon in a nitrogen atmosphere. The as-prepared composites were studied by X-ray powder diffraction（XRD）, X-ray photoelectron spectroscopy（XPS） and transmission electron microscopy（TEM）. The capacitive property of the composites was investigated by cyclic voltammetry（CV） and galvanostatic charge-discharge test. Physical characterizations show that the γ-Fe2O3 fine grains dispersed in the AC well, with a mean size of 21.24 nm. Electrochemical tests in 6 mol/L KOH solutions indicate that the as-prepared nanocomposites exhibited improved capacitive properties. The specific capacitance（SC） of Fe2O3/AC nanocomposites was up to 188.4 F/g that was derived from both electrochemical double-layer capacitance and pseudo-capacitance, which was 78% larger than that of pristine AC. A symmetric capacitor with Fe2O3/AC nanocomposites as electrode showed an excellent cycling stability. The SC was only reduced by a factor of 9.2% after 2000 cycles at a current density of 1 A/g.

Preparation of spherical activated carbon-supported and Er^(3+):YAlO_3-doped TiO_2 photocatalyst for methyl orange degradation under visible light

In order to develop the high photocatalytic activity of TiO2 under visible light as that under ultraviolet light and make it easy to be separated from treated liquor, a visible light response and spherical activated carbon （SAC） supported photocatalyst doped with upconversion luminescence agent Er3＋：YAlO3 was prepared by immobilizing Er3＋：YAlO3/TiO2, which was obtained by combination of Er3＋：YAlO3 and TiO2 using sol-gel method, on the surface of SAC. The crystal phase composition, surface structure and element distribution, and light absorption of the new photocatalysts were examined by X-ray diffraction （XRD）, energy dispersive X-ray spectra （EDS） analysis, scanning electron microscopy （SEM） and fluorescence spectra analysis （FSA）. The photocatalytic oxidation activity of the photocatalysts was also evaluated by the photodegradation of methyl orange （MO） in aqueous solution under visible light irradiation from a LED lamp （λ400 nm）. The results showed that Er3＋：YAlO3 could perform as the upconversion luminescence agent which converts the visible light up to ultraviolet light. The Er3＋：YAlO3/TiO2 calcinated at 700 °C revealed the highest photocatalytic activity. The apparent reaction rate constant could reach 0.0197 min-1 under visible light irradiation.

Photocatalytic activity and kinetics for acid yellow degradation over surface composites of TiO_2-coated activated carbon under different photocatalytic conditions

TiO2-coated activated carbon surface （TAs） composites were prepared by a sol-gel method with supercritical pretreatment. The photocatalytic degradation of acid yellow （AY） was investigated under UV radiation to estimate activity of catalysts and determine the kinetics. And the effects of parameters including the initial concentration of AY, light intensity and TiO2 content in catalysts were examined. The results indicate that TAs has a higher efficiency in decomposition of AY than P25, pure TiO2 particles as well as the mixture of TiO2 powder and active carbon. The photocatalytic degradation rate is found to follow the pseudo-first order kinetics with respect to the AY concentration. The new kinetic model fairly resembles the classic Langmuir-Hinshelwood equation, and the rate constant is proportional to the square root of the light intensity in a wide range. However, its absorption performance depends on the surface areas of catalysts. The model fits quite well with the experimental data and elucidates phenomena about the effects of the TiO2 content in TAs on the degradation rate.

PBST/TiO_(2)/MgO复合薄膜的制备及性能

采用硅烷偶联剂γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH-570)对TiO_(2)/MgO NPs改性,采用溶液共混法制备了聚丁二酸-共-对苯二甲酸丁二醇酯(PBST)/TiO_(2)/MgO NPs纳米复合薄膜,并探讨了其在食品包装方面的应用。研究了改性TiO_(2)/MgO NPs对PBST基体机械、阻隔、抗菌和保鲜性能的影响。结果表明:复合膜的抗拉强度和水蒸汽透过率分别为29.39MPa和2.43×10^(-11) g·m/(m^(2)·s·Pa),相较PBST基体抗拉强度提高了24.32%,水蒸汽透过率降低了32.37%,且对金黄色葡萄球菌(S.aures)和大肠杆菌(E.coli)抑菌效果显著,分别达到98.7%和97.2%,并对圣女果有良好的保鲜性能,当改性后的TiO_(2)/MgO NPs质量含量为5%时,复合薄膜的性能最佳。

Carbon Doped Nano-Crystalline TiO₂Photo-Active Thin Film for Solid State Photochemical Solar Cells

Carbon doped titanium dioxide (C-TiO2) is considered as a promising photocatalytic material due to its optical absorption extended in the visible region compared to pure TiO2. However, in the field of photovoltaic’s, use of C-doped nano-crystalline titanium dioxide (C-TiO2) electrodes for light absorption has been considered to be unnecessary so far. In this context, we report here on the use of C-TiO2 nano-crystalline electrodes in photochemical solar cells devices (PCSC). Carbon doping has reduced the band gap of TiO2 to 2.41 eV and 2.25 eV with increase in the doping extent for the 9 mM C-TiO2 and 45 mM C-TiO2 respectively. The C-TiO2 electrodes were first used as photo electrodes for solar cells, exhibiting JSC of 1.34651 mA/cm2, VOC 0.683 V, FF 50.23% and η 0.46%. for the 9 mM C-TiO2 and exhibiting JSC of 1.34651 mA/cm2, VOC 0.815 V, FF 54.3% and η 0.59% for the 45 mM C-TiO2. The fabricated solar cell devices have shown an increase in VOC of up to 0.815 V, which is higher than that of 0.7 V for dye sensitized solar cells. The doping of carbon in TiO2 lattice was closely studied by SEM, XRD, RS and UV-Vis spectroscopy.

A general descriptor for guiding the electrolysis of CO_(2)in molten carbonate

Molten carbonate is an excellent electrolyte for the electrochemical reduction of CO_(2)to carbonaceous materials.However,the electrolyte–electrode-reaction relationship has not been well understood.Herein,we propose a general descriptor,the CO_(2)activity,to reveal the electrolyte–electrode-reaction relationship by thermodynamic calculations and experimental studies.Experimental studies agree well with theoretical predictions that both cations(Li^(+),Ca^(2+),Sr^(2+)and Ba^(2+))and anions(BO_(2)^(-),Ti_(5)O_(14)^(8-),SiO_(3)^(2-))can modulate the CO_(2)activity to control both cathode and anode reactions in a typical molten carbonate electrolyzer in terms of tuning reaction products and overpotentials.In this regard,the reduction of CO_(3)^(2-)can be interpreted as the direct reduction of CO_(2)generated from the dissociated CO_(3)^(2-),and the CO_(2)activity can be used as a general descriptor to predict the electrode reaction in molten carbonate.Overall,the CO_(2)activity descriptor unlocks the electrolyte–electrode-reaction relationship,thereby providing fundamental insights into guiding molten carbonate CO_(2)electrolysis.

Mechanism study on the influence of surface properties on the synthesis of dimethyl carbonate from CO_(2)and methanol over ceria catalysts

The direct synthesis of dimethyl carbonate(DMC)from CO_(2)and methanol has attracted much attention as an environmentally benign and alternative route for conventional routes.Herein,a series of cerium oxide catalysts with various textural features and surface properties were prepared by the one-pot synthesis method for the direct DMC synthesis from CO_(2)and methanol,and the structure-performance relationship was investigated in detail.Characterization results revealed that both of surface acid-base properties and the oxygen vacancies contents decreased with the rising crystallinity at increasingly higher calcination temperature accompanied by an unexpectedly volcano-shaped trend of DMC yield observed on the catalysts.In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)studies indicated that the adsorption rate of methanol is slower than that of CO_(2)and the methanol activation state largely influences the formation of key intermediate.Although the enhanced surface acidity-basicity and oxygen vacancies brought by low-temperature calcination could facilitate the activation of CO_(2),the presence of excess strongly basic sites on low-crystallinity sample was detrimental to DMC synthesis due to the preferred formation of unreactive mono/polydentate carbonates as well as the further impediment of methanol activation.Moreover,with the use of 2-cyanopyridine as a dehydration reagent,the DMC synthesis was found to be both influenced by the promotion from the rapid in situ removal of water and the inhibition from the competitive adsorption of hydration products on the same active sites.

TiO_(2)/AC光催化降解PTA精制废水的实验研究

针对精对苯二甲酸(PTA)精制废水净化处理难问题,提出一种新型光催化降解处理方法。采用两步法制备TiO_(2)/活性炭(AC)复合催化剂,并利用X—射线衍射光谱(XRD)、N2吸附脱附和扫描电镜(SEM)对制备的复合催化剂进行表征。在光反应装置中进行光催化降解实验,考察TiO_(2)/AC的光催化性能。结果表明:锐钛矿晶型的TiO_(2)分散于AC丰富的微孔和中孔中;最佳光催化反应条件为焙烧温度为500℃,AC粒径为(0.2,0.3]mm,紫外灯功率为40 W,TiO_(2)负载量为11%,催化剂质量浓度为7 g/L,光照时间7 h,此时PTA精制废水的化学需氧量(COD)去除率达64.24%;同时,TiO_(2)/AC复合催化剂展现出良好的重复使用性能,证明了TiO_(2)/AC光催化处理方法的可行性和高效性。

Microwave photocatalytic degradation of Rhodamine B using TiO_2 supported on activated carbon:Mechanism implication

The photocatalytic degradation of Rhodamine B （RhB） was carried out using TiO2 supported on activated carbon （TiO2-AC） under microwave irradiation. Composite catalyst TiO2-AC was prepared and characterized using X-ray diffraction （XRD）, transmission electron microscopy （TEM） and Brunauer-Emmett-Teller （BET）. In the process of microwave-enhanced photocatalysis （MPC）, RhB （30 mg/L） was almost completely decoloured in 10 min, and the mineralization efficiency was 96.0% in 20 min. The reaction rate constant of RhB in MPC using TiO2-AC by pseudo first-order reaction kinetics was 4.16 times of that using Degussa P25. Additionally, according to gas chromatography/mass spectrometry （GC/MS） and liquid chromatography/mass spectrometry （LC/MS） identification, the major intermediates of RhB in MPC included two kinds of N-de-ethylation intermediates （N,N-diethyl-N＇-ethyl-rhodamine （DER））, oxalic acid, malonic acid, snccinic acid, and phthalic acid, maleic acid, 3-nitrobenzoic acid, and so on. The degradation of RhB in MPC was mainly attributed to the destruction of the conjugated structure, and then the intermediates transformed to acid molecules which were mineralized to water and carbon dioxide.

Inactivated properties of activated carbon-supported TiO_2 nanoparticles for bacteria and kinetic study

The activated carbon-supported TiO2 nanoparticles(TiO2/AC)were prepared by a properly controlled sol-gel method.The effects of activated carbons(AC)support on inactivated properties of TiO2 nanoparticles were evaluated by photocatalytic inactivation experiments of Escherichia coli.The key factors affecting the inactivation effciency were investigated,including electric power of lamp, temperature,and pH values.The results show that the TiO2/AC composites have high inactivation properties of E.coli in compari...

Preparation of activated carbons and their adsorption properties for greenhouse gases:CH_4 and CO_2

Three kinds of activated carbons were prepared using coconut-shells as carbon precursors and characterized by XRD, FT-IR and texture property test. The results indicate that the prepared activated carbons were mainly amorphous and only a few impurity groups were adsorbed on their surfaces. The texture property test reveals that the activated carbons displayed different texture properties, especially the micropore size distribution. The adsorption capacities of the activated carbons were investigated by adsorbing CH4, CO2, N2 and O2 at 25 ？C in the pressure range of 0-200 kPa. The results reveal that all the activated carbons had high CO2 adsorption capacity, one of which had the highest CO2 adsorption value of 2.55 mmol/g at 200 kPa. And the highest adsorption capacity for CH4 of the activated carbons can reach 1.93 mmol/g at 200 kPa. In the pressure range of 0-200 kPa, the adsorption capacities for N2 and O2 were increased linearly with the change of pressure and K-AC is an excellent adsorbent towards the adsorption separation of greenhouse gases.

Characteristic and mercury adsorption of activated carbon produced by CO_2 of chicken waste

Preparation of activated carbon from chicken waste is a promising way to produce a useful adsorbent for Hg removal. A three-stage activation process （drying at 200℃, pyrolysis in N2 atmosphere, followed by CO2 activation） was used for the production of activated samples. The effects of carbonization temperature （409-4500℃）, activation temperature （700-900℃）, and activation time （1-2.5 h） on the physicochemical properties （weight-loss and BET surface） of the prepared carbon wereinvestigated. Adsorptive removal of mercury from real flue gas onto activated carbon has been studied. The activated carbon from chicken waste has the same mercury capacity as commercial activated carbon （Darco LH） （Hg^v： 38.7% vs. 53.5%, Hg^0： 50.5% vs. 68.8%）, although its surface area is around 10 times smaller, 89.5 m^2/g vs. 862 m^2/g. The low cost activated carbon can be produced from chicken waste, and the procedure is suitable.

Adsorption of Cd^(2+) in aqueous solutions using KMnO_4-modified activated carbon derived from Astragalus residue

Activated carbon obtained from Astragalus residue was chemically activated by KOH and modified with KMnO4.The samples were characterized by N2 adsorption,Fourier transform infrared spectroscopy,X-ray diffractometry,scanning electron microscopy,and Boehm titration.Accordingly,the original and modified carbon materials were used for the removal of Cd2+from aqueous solution by batch adsorption experiments.Results showed that the contents of oxygen-containing functional groups increased,and MnO2 was nearly uniformly deposited on the surface of activated carbon after modification by KMnO4.The adsorption kinetics was described by pseudo-second order model.Langmuir model fitted the adsorption-isotherm experimental data of Cd2+better than the Freundlich model.The maximum adsorption capacities of the activated carbon before and after modification for Cd2+were 116.96 and 217.00 mg/g,respectively.KMnO4 considerably changed the physicochemical properties and surface texture of activated carbon and enhanced the adsorption capacity of activated carbon for Cd2+.

Photocatalytic degradation of L- acid by TiO_2 supported on the activated carbon

TiO2 sol was prepared by sol-gel technique with tetrabutyl titanate as precursor. Supported TiO2 catalysts on activated carbon were prepared by soak and sintering method. The aggregation of nano-TiO2 particles can be effectively suppressed by added polyethylene glycol （PEG） as a surface modifier. The average particle diameter of TiO2, specific surface area and absorbability of catalyst can be modified. Based on characteristics of the TiO2 photocatalyst with XRD, specific surface area, adsorption valves of methylene blue and the amount of TiO2 supported on the activated carbon, the photocatalytic degradation of L-acid was studied. The effect of the factors, such as pH of the solution, the initial concentration of L-acid on the photocatalytic degradation of L-acid, were studied also. It was found that when the pH of the solution is 1.95, the amount of photocatalyst is 0.5 g, the concentration of the L-acid solution is 1.34×10^3 mol/L and the illumination time is 7 h, the photocatalytic degradation efficiency of L-acid can reach 89,88%, The catalyst was reused 6 times and its degradation efficiency hardly changed.