基于生物碳化活性氧化镁技术抑制土体干缩开裂的试验研究

在干燥环境下,土体表面裂隙的产生能够极大弱化土体的力学性质,进而引发各类工程地质问题。文章研究了基于喷洒法处理的生物碳化活性氧化镁技术在抑制土体干缩开裂方面的可行性,并探究了材料组分、尿素浓度、活性氧化镁用量和喷洒顺序对土体抗裂性能的影响。研究结果表明:(1)活性氧化镁生物碳化产物水合碳酸镁的形成增强了土颗粒间的胶结,并在土体表面形成生物碳化防护层,通过降低土体中水分的蒸发速率和提高土体的抗拉强度,能够有效抑制土体的干缩开裂行为;(2)尿素浓度的升高能够显著促进活性氧化镁的生物碳化。当尿素浓度为2.0 mol/L时,经三轮干湿循环后,处理试样的最大贯入阻力相较于未处理试样提升了195.5%;(3)高的活性氧化镁用量和活性氧化镁溶液后喷洒的处理方式均会降低活性氧化镁在土体内部的入渗能力,从而显著影响土体的胶结效果。

表面活性剂碳化法合成Fe_3O_4/C复合物及其电化学性能

以水热法合成的包覆油酸的α-Fe2O3粒子为前驱体,在氩气下500°C煅烧1h,得到Fe3O4/C纳米复合物.用傅里叶变换红外(FTIR)光谱,X射线衍射(XRD),扫描电镜(SEM),X射线能量散射(EDX)谱,高分辨透射电镜(HRTEM),元素分析,循环伏安(CV)和恒流充放电测试等方法对材料的结构、形貌、成分及电化学性能进行了表征.结果表明:所制备的Fe3O4/C复合物呈长约200nm,粗约100nm的纺锤形,表面碳层厚约1-2nm,碳含量为1.956%(质量分数);这种复合物作为锂离子电池负极材料具有很好的循环稳定性(在0.2C(1C=928相mA对·于g-1未)循包环覆8的0次商后业具Fe有3O649粒1子.7,m复A合h·物g-显1比著容提量高)和的倍电率化性学能性(能在是2C由循于环碳2包0覆次能后防依止然粒有子52聚0集mA,提h·高g-导1比电容性量以).及稳定固体电解质界面(SEI)膜.

不锈钢渣碳化影响因素及其机理研究

为开发γ-C_(2)S不锈钢渣碳储存的潜力,最大限度地提高不锈钢渣的综合利用率。通过研究主要碳化参数(如液固比、成型压力、CO_(2)分压)对不锈钢渣碳化性能的影响规律来评估不锈钢渣的CO_(2)储存能力,以期能够提供更佳的不锈钢渣碳化过程。利用XRD、SEM/EDS、DSC/TG分析对不锈钢渣碳化产物组成及微观形貌进行表征,并探索其碳化机理。结果表明,较佳碳化参数为成型压力为2.50 MPa,液固比为10%,CO_(2)分压为0.3 MPa。较佳碳化条件下每千克不锈钢渣可固化储存CO_(2)气体约123.6 g。不锈钢渣碳化过程以γ-C_(2)S碳化反应为主,碳化产物中出现了片状、颗粒状的CaCO_(3),随碳化时间延长,晶体逐渐长大为团簇状。因此,利用不锈钢渣储备碳及制备碳化制品是可行的。

三种废渣的CO_(2)矿化封存性能及制备胶凝材料

阳江市是华南地区重要基础原材料生产基地,产生电炉镍铁渣、高炉镍铁渣和不锈钢精炼渣三种废渣。本文对比分析三种废渣在干法和湿法矿化封存CO_(2)差异性,评估三种废渣碳化后制备胶凝材料可行性。研究表明:干法固碳中,不锈钢精炼渣、高炉镍铁渣和电炉镍铁渣矿化封存CO_(2)能力逐渐降低,碳化时间24h时,CO_(2)封存量分别为150g/kg、25g/kg、23g/kg;湿法固碳中,电炉镍铁渣和高炉镍铁渣固碳率与干法相似,不锈钢精炼渣固碳率随液固比增加出现先升高后降低趋势。三种废渣碳化后其胶凝活性均降低,且不锈钢精炼渣降低幅度更显著,28d活性指数降幅分别为21.9%、21.7%、35.7%。

硅质组分对再生胶凝材料碳化反应活性的影响

引入不同结晶形态的硅质组分(结晶状二氧化硅和无定形硅灰)调节再生胶凝材料(RBMs)中游离氧化钙(f-CaO)的含量,研究了其对碳化反应活性、力学性能和微观结构特征的影响。结果表明:分别掺入2种硅质组分制备的RBMs碳化后基体稳定性均得到了显著改善;掺入结晶状二氧化硅制备的RBMs碳化后抗压强度和抗折强度分别为73.1 MPa和21.0 MPa,碳化反应形成的碳酸钙晶体以球霰石和方解石为主;掺入硅灰制备的RBMs,抗压强度提高了45.42%至106.3 MPa,抗折强度提高了20.55%至25.3MPa,并且碳酸钙晶体以球霰石为主,含少量方解石和文石;高碳化反应活性、高碳化程度、结构致密是掺入硅灰制备的RBMs力学性能提升的主要原因。

Effects of preparation temperature on electrochemical performance of nitrogen-enriched carbons

The activated nitrogen-enriched novel carbons (NENCs) were prepared by direct carbonization using polyaniline coating activated mesocarbon microbead composites as the precursor. Herein the influences of the carbonization temperature on the structure and morphology of the NENCs samples were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N2 adsorption/desorption isotherm at 77 K. The electrochemical properties of the supercapacitors were characterized by cyclic voltammetry, galvanostatic charge/discharge, electrochemical impedance spectroscopy (EIS), cycle life, leakage current and self-discharge measurements in 6 mol/L KOH solution. The results demonstrate that the NENC samples carbonized at 600 °C show the highest specific capacitance of 385 F/g at the current density of 1 A/g and the lowest ESR value (only 0.93?). Furthermore, the capacity retention ratio of the NENCs-600 supercapacitor is 92.8 % over 2500 cycles.

Soil Carbon Pool Management Index under Different Straw Retention Regimes

[Objective] To clarify the effects of different straw retention regimes on soil fertility in double cropping paddy field. [Method] The effects of different straw reten- tion regimes on total organic carbon （CToc）, active carbon （CA） and mineralized carbon （CM） were analyzed, and carbon pool active （A）, carbon pool active index （A/）, carbon pool index （CPI） and carbon pool management index （CPMi） for each treat- ment were calculated. [Result] Compared with the unfertilized treatment （CK）, CToc, CA, CM and the available ratio of soil carbon were increased in the treatment of re- turning early season and late season rice straws to field. With the same nutrient application, CToc, CA and the available ratio of soil carbon in the field with straw re- turned to field were higher than that of straw incineration and no straw returning, and the change in soil CA content was more significant. The difference in CPMI be- tween different treatments reached significant or very significant level, and the value was in the order of straw directly returned to field 〉 straw returned to field after in- cineration 〉 no straw returned to field. [Conclusion] This study provided theoretical bases for the increase of soil CA content and soil fertility in double rice fields.

Modification of ACFs by chemical vapor deposition and its application for removal of methyl orange from aqueous solution

Viscose activated carbon fibers （ACFs） were characterized using specific surface area, scanning electron modified with chemical vapor deposition （CVD）. The samples were microscopy （SEM）, pore size distribution and Fourier transform infrared spectroscopy （FTIR）. Batch adsorption experiments were carried out to investigate the adsorption behavior of modified ACFs for methyl orange（MO） from its aqueous solutions. The results show that the adsorption isotherms of MO onto modified ACFs well follows the Langmuir isotherm equation. The adsorption kinetics of MO can be well described by the pseudo second-order kinetic model. The adsorption process involves the intra-particle diffusion, but is not the only rate-controlling step. Thermodynamic parameters including AG, AH and AS were calculated, suggesting that the adsorption of MO onto modified ACFs is a spontaneous, exothermic and physisorption process. FTIR result indicates that the major adsorption mechanism of modified ACFs for MO is hydrogen bond.

SnO_2 nano-sheet as an efficient catalyst for CO oxidation

Polycrystalline SnO2 fine powder consisting of nano-particles （SnO2-NP）, SnO2 nano-sheets （SnO2-NS）, and SnO2 containing both nano-rods and nano-particles （SnO2-NR＋NP） were prepared and used for CO oxidation. SnO2-NS possesses a mesoporous structure and has a higher surface area, larger pore volume, and more active species than SnO2-NP, and shows improved activity. In contrast, although SnO2-NR＋NP has only a slightly higher surface area and pore volume, and slightly more active surface oxygen species than SnO2-NP, it has more exposed active （110） facets, which is the reason for its improved oxidation activity. Water vapor has only a reversible and weak influence on SnO2-NS, therefore it is a potential catalyst for emission control processes.

Effects of Co_3O_4 nanocatalyst morphology on CO oxidation:Synthesis process map and catalytic activity

This study focuses on drawing a hydrothermal synthesis process map for Co3O4 nanoparticles with various morphologies and investigating the effects of Co3O4 nanocatalyst morphology on CO oxidation.A series of cobalt-hydroxide-carbonate nanoparticles with various morphologies（i.e.,nanorods,nanosheets,and nanocubes） were successfully synthesized,and Co3O4 nanoparticles were obtained by thermal decomposition of the cobalt-hydroxide-carbonate precursors.The results suggest that the cobalt source is a key factor for controlling the morphology of cobalt-hydroxide-carbonate at relatively low hydrothermal temperatures（≤ 140℃）.Nanorods can be synthesized in CoCl2 solution,while Co（NO3）2 solution promotes the formation of nanosheets.Further increasing the synthesis temperature（higher than 140 ℃） results in the formation of nanocubes in either Co（NO3）2 or CoCl2 solution.The reaction time only affects the size of the obtained nanoparticles.The presence of CTAB could improve the uniformity and dispersion of particles.Co3O4 nanosheets showed much higher catalytic activity for CO oxidation than nanorods and nanocubes because it has more abundant Co^（3＋） on the surface,much higher reducibility,and better oxygen desorption capacity.

Octahedral Cu_2O-modified TiO_2 nanotube arrays for efficient photocatalytic reduction of CO_2

A photocatalyst composed of TiO 2 nanotube arrays（TNTs） and octahedral Cu2 O nanoparticles was fabricated,and its performance in the photocatalytic reduction of CO2 under visible and simulated solar irradiation was studied. The average nanotube diameter and length was 100 nm and 5 μm,respectively. The different amount of octahedral Cu2 O modified TNTs were obtained by varying electrochemical deposition time. TNTs modified with an optimized amount of Cu2 O nanoparticles exhibited high efficiency in the photocatalysis,and the predominant hydrocarbon product was methane. The methane yield increased with increasing Cu2 O content of the catalyst up to a certain deposition time,and decreased with further increase in Cu2 O deposition time. Insufficient deposition time（5 min） resulted in a small amount of Cu2 O nanoparticles on the TNTs,leading to the disadvantage of harvesting light. However,excess deposition time（45 min） gave rise to entire TNT surface being most covered with Cu2 O nanoparticles with large sizes,inconvenient for the transport of photo-generated carriers. The highest methane yield under simulated solar and visible light irradiation was observed for the catalysts prepared at a Cu2 O deposition time of 15 and 30 min respectively. The morphology,crystallization,photoresponse and electrochemical properties of the catalyst were characterized to understand the mechanism of its high photocatalytic activity. The TNT structure provided abundant active sites for the adsorption of reactants,and promoted the transport of photogenerated carriers that improved charge separation. Modifying the TNTs with octahedral Cu2 O nanoparticles promoted light absorption,and prevented the hydrocarbon product from oxidation. These factors provided the Cu2O-modified TNT photocatalyst with high efficiency in the reduction of CO2,without requiring co-catalysts or sacrificial agents.

Science Letters:Effect of nitrogen doping on the reduction of nitric oxide with activated carbon in the presence of oxygen

Nitrogen doping of activated carbon （AC） was performed by annealing both in ammonia and nitric oxide, and the activities of the modified carbons for NO reduction were studied in the presence of oxygen. Results show that nitrogen atoms were incorporated into the carbons, mostly in the form of pyridinic nitrogen or pyridonic nitrogen. The effect of nitrogen doping on the activities of the carbons can be ignored when oxygen is absent, but the doped carbons show desirable activities in the low temperature regime （≤500 ℃） when oxygen is present. The role of the surface nitrogen species is suggested to promote the formation of NO2 in the presence of oxygen, and NO2 can facilitate decomposition of the surface oxygen species in the low temperature regime

Copper-ceria solid solution with improved catalytic activity for hydrogenation of CO to CHOH

A copper-ceria solid solution and ceria-supported copper catalysts were prepared and used for the catalytic hydrogenation of CO2 to CH3OH.According to site-specific classification and quantitative analyses(X-ray diffraction,Raman spectroscopy,X-ray photoelectron spectroscopy,H2 temperature-programmed reduction,and CO adsorption),the interfaces of the prepared catalysts were classified as Cu incorporated into ceria(Cu-Ov-Cex),dispersed Cu O(D-Cu O-Ce O2),and bulk Cu O(B-Cu O-Ce O2)over the Ce O2 surface.These results,together with those of activity tests,showed that the Cu-Ov-Cex species was closely related to the CO2 hydrogenation activity and resulted in a much higher turnover frequency of CH3OH production than that observed with the D-Cu O-Ce O2 and B-Cu O-Ce O2 species.Thus,the copper-ceria solid solution exhibited improved activity due to the higher Cu-Ov-Cex fraction.

The Enhancement of CO2 Chemical Absorption by K2CO3 Aqueous Solution in the Presence of Activated Carbon Particles

The enhancement of chemical absorption of CO2 by K2CO3/H2O absorbents in the presence of activated carbon （AC） particles was investigated. The results show that the gas absorption rates can be enhanced significantly in the presence of AC particles, and the maximum enhancement factor 3.7 was observed at low stirring intensities. The enhancement factor increased rapidly with the solid loading during the initial period of absorption and then be- came mild gradually to a maximum value. Both the liquid-solid contact area and the probability of solid particles residing at the gas-liquid interface decreased with the increase of the particle size, leading to a negative effect on the enhancement of mass transfer. The influence of the particles on gas absorption decreased with the reaction rate. The stirring speed changed the interfacial coverage and mass transfer rate on the liquid side and consequently affected the mass transfer between the gas and liquid phases; the enhancement factor decreased with the stirring intensity. A heterogeneous two-zone model was proposed for predicting the enhancement factor and the calculated results agreed well with the experimental data.

Synthesis of acetals and ketals catalyzed by tungstosilicic acid supported on active carbon

Catalytic activity of activated carbon supported tungstosilicic acidin synthesizing 2-methyl-2-ethoxycarbonylmethyl- 1,3-dioxolane, 2,4-dimethyl-2-ethoxycarbonylmethyl-1,3-dioxolane, cyclohexanone ethylene ketal, cyclohexanone 1,2-propa- nediol ketal, butanone ethylene ketal, butanone 1,2-propanediol ketal, 2-phenyl-1,3-dioxolane, 4-methyl-2-phenyl-1,3-dioxolane, 2-propyl-1,3-dioxolane, 4-methyl-2-propyl-1,3-dioxolane was reported. It has been demonstrated that activated carbon supported tungstosilicic acid is an excellent catalyst. Various factors involved in these reactions were investigated. The optimum conditions found were: molar ratio of aldehyde/ketone to glycol is 1/1.5, mass ratio of the catalyst used to the reactants is 1.0%, and reaction time is 1.0 h. Under these conditions, the yield of 2-methyl-2-ethoxycarbonylmethyl-1,3-dioxolane is 61.5%, of 2,4-dimethyl- 2-ethoxycarbonylmethyl-1,3-dioxolane is 69.1%, of cyclohexanone ethylene ketal is 74.6%, of cyclohexanone 1,2-propanediol ketal is 80.1%, of butanone ethylene ketal is 69.5%, of butanone 1,2-propanediol ketal is 78.5%, of 2-phenyl-1,3-dioxolane is 56.7%, of 4-methyl-2-phenyl-1,3-dioxolane is 86.2%, of 2-propyl-1,3-dioxolane is 87.5%, of 4-methyl-2-propyl-1,3-dioxolane is 87.9%.

Kinetic study on carbothermic reduction of ilmenite with activated carbon

The carbothermic reduction of Panzhihua ilmenite with various additions of activated carbon was investigated byisothermal experiments over the temperature range of1373to1773K in the argon atmosphere.According to the reaction kineticsrecorded by the infrared gas analyzer,it was found that the amount of carbon addition had little influence on the reaction rates atvarious temperatures except1473K.When the reaction temperature was above the eutectic temperature of1427K of Fe?C binarysystem,part of carbon would dissolve into Fe to form a liquid phase,which made the liquid Fe as a diffusion channel of carbon todiffuse to the reaction interface.The carbothermic reduction above1573K obeyed the shrinking-core model.The mass fraction ofTiC could be determined by the standard addition technique.

Effect of Pre-oxidation on the Properties of Crushed Bituminous Coal and Activated Carbon Prepared Therefrom

The influence of a pre-oxidation process on the chemical properties of crushed bituminous coal and on adsorption properties of the subsequently formed char and activated carbon is discussed in this paper. Datong bituminous coal samples sized 6 mm were oxidized at different temperatures and for different times and then carbonized and activated by steam to obtain activated carbons. A Uniform Design method was used to arrange the experiments,IR and adsorption experiments were used to characterize these oxidized coals,chars and activated carbon samples. The results show that the carboxyl group disappeared and α-CH2 groups joined to alkenes decreased dramatically but the carbonyl group clearly increased in the coal sample oxidized at 543 K; The chemical composition of coal samples oxidized at lower temperature is different from that of coal oxidized at 543 K. Oxidizing coal samples at higher temperatures for a short time or at lower temperatures for a longer time resulted in activated carbon samples that tended toward the same adsorption properties: Iodine number 1100 mg/g and Methylene blue value 252 mg/g. The yield of activated carbon obtained from the pre-oxidized coal is 10% higher than the yield from parent coal but the activated carbons have the same adsorption properties.

Mechanism and active sites of CO oxidation over single-crystal Au surfaces and a Au/TiO_2(110) model surface

We describe the reaction mechanism and active sites for CO oxidation over a Au/TiO2（110） model surface and Au single‐crystal surfaces, along with the role of H2O, on a molecular scale. At low tem‐perature （＆lt;320 K）, H2O played an essential role in promoting CO oxidation, and the active site for CO oxidation was the perimeter of the interface between the gold nanoparticles and the TiO2 sup‐port （Auδ＋–Oδ––Ti）. We believe that the O–O bond was activated by the formation of OOH, which was produced directly from O2 and H2O at the perimeter of the interface between the gold nanoparticles and the TiO2 support, and consequently OOH reacted with CO to form CO2. This reaction mechanism explains the dependence of the CO2 formation rate on O2 pressure at 300 K. In contrast, at high temperature （＆gt;320 K）, low‐coordinated gold atoms built up on the surface as a result of surface reconstruction due to exposure to CO. The low‐coordinated gold atoms adsorbed O2, which then dissociated and oxidized CO on the metallic gold surface.

Reactivities of Shenfu Chars Toward Gasification with Carbon Dioxide

Five Shenfu char samples were prepared from Shenfu raw coal at different temperatures （950, 1100, 1200, 1300 and 1400℃） using a muffle furnace. Demineralization of the char samples was performed by treating them with 10% nitric acid for 10 min in a CEM Discover microwave reactor. The gasification of the chars, and corresponding demineralized chars, in a carbon dioxide （CO2） atmosphere was conducted in a Netzsch STA 409Cl31F tempera- ture-programmed thermogravimetry apparatus. The effects of charring temperature and demineralization on the gasification reactivity of chars were systematically investigated. The results show that a char formed at a lower temperature is more reactive except for demineralized char formed at 1100℃, which is less reactive than char formed at 1200℃. Demineralization decreases the char reactivities toward gasification with CO2 to a small extent.

Doping-induced metal–N active sites and bandgap engineering in graphitic carbon nitride for enhancing photocatalytic H_(2 )evolution performance

Durable and inexpensive graphitic carbon nitride(g-C_(3)N_(4))demonstrates great potential for achieving efficient photocatalytic hydrogen evolution reduction(HER).To further improve its activity,g-C_(3)N_(4)was subjected to atomic-level structural engineering by doping with transition metals(M=Fe,Co,or Ni),which simultaneously induced the formation of metal-N active sites in the g-C_(3)N_(4)framework and modulated the bandgap of g-C_(3)N_(4).Experiments and density functional theory calculations further verified that the as-formed metal-N bonds in M-doped g-C_(3)N_(4)acted as an"electron transfer bridge",where the migration of photo-generated electrons along the bridge enhanced the efficiency of separation of the photogenerated charges,and the optimized bandgap of g-C_(3)N_(4)afforded stronger reduction ability and wider light absorption.As a result,doping with either Fe,Co,or Ni had a positive effect on the HER activity,where Co-doped g-C_(3)N_(4)exhibited the highest performance.The findings illustrate that this atomic-level structural engineering could efficiently improve the HER activity and inspire the design of powerful photocatalysts.