Adsorption performances and refrigeration application of adsorption working pair of CaCl_2-NH_3

Adsorption refrigeration is an environment benign and cost-effective way for waste heat recovery and solar energy utilization[1].The adsorption working pairs mainly include activated carbon-methanol, activated carbon-ammonia, zeolite-water, CaCl2-NH3, etc. The working pair of CaCl2-NH3 has such advantages as large sorption quantity and fast sorption rate[2—5]. However, it has also disadvantages of swelling, disintegration and agglomeration, which are the main obstacles to its application[6…     

Mg<Subscript>2</Subscript>(OH)<Subscript>2</Subscript>CO<Subscript>3</Subscript>·3H<Subscript>2</Subscript>O whiskers growth mechanism

From the perspective of growth units, the growth mechanism of Mg₂(OH)₂CO₃·3H₂O whisker is investigated in this paper. Results show that the growth morphology of Mg₂(OH)₂CO₃·3H₂O whisker is consistent with the model of anion coordination polyhedron growth units. The growth solution Raman shift of Mg₂(OH)₂CO₃·3H₂O was monitored using Raman spectroscopy. The growth units are [Mg-(OH)₄]^2- and H₂CO₃. The growth process of Mg₂(OH)₂CO₃·3H₂O whisker is as follows: growth unit [Mg-(OH)₄]^2- first incorporates into the larger dimension [Mg-(OH)₄] _n ^2- , then the [Mg-(OH)₄] _n ^2- combines with H₂CO₃ into a linear skeleton Mg₂(OH)₂CO₃ in the same line. Mg₂(OH)₂CO₃ combines with H₂O by hydrogen bonds and ultimately transforms into Mg₂(OH)₂CO₃·3H₂O whisker. Magnesium carbonate whiskers have a layered structure, each of which is made of magnesium, carbon, oxygen, with H₂O in between each layer. When skeletons are superimposed within the same plane as a parallelepiped one, they grow into solid cuboid-shaped whiskers. When the parallelepiped skeletons planes combine with each other through the cascading links, they grow into hollow cylindrical whiskers.     

Preparation and thermoelectric properties of SiO<Subscript>2</Subscript>/<Emphasis Type="Italic">β</Emphasis>-Zn<Subscript>4</Subscript>Sb<Subscript>3</Subscript> nanocomposite materials

A series of SiO₂/β-Zn₄Sb₃ core-shell composite particles with 3, 6, 9, and 12 nm of SiO₂ shell in thickness were prepared by coating β-Zn₄Sb₃ microparticles with SiO₂ nanoparticles formed by hydrolyzing the tetraethoxysilane in alcohol-alkali-water solution. SiO₂/β-Zn₄Sb₃ nanocomposite thermoelectric materials were fabricated with these core-shell composite particles by spark plasma sintering (SPS) method. Microstructure, phase composition, and thermoelectric properties of SiO₂/β-Zn₄Sb₃ nanocomposite thermoelectric materials were systemically investigated. The results show that β-Zn₄Sb₃ microparticles are uniformly coated by SiO₂ nanoparticles, and no any phase transformation reaction takes place during SPS process. The electrical and thermal conductivity gradually decreases, and the Seebeck coefficient increases compared to that of β-Zn₄Sb₃ bulk material, but the increment of Seebeck coefficient in high temperature range remarkably increases. The thermal conductivity of SiO₂/β-Zn₄Sb₃ nanocomposite material with 12 nm of SiO₂ shell is the lowest and only 0.56 W·m⁻¹·K⁻¹ at 460 K. As a result, the ZT value of the SiO₂/β-Zn₄Sb₃ nanocomposite material reaches 0.87 at 700 K and increases by 30%.     

Structural and electrochemical performances of <Emphasis Type=Italic>α</Emphasis>-MnO<Subscript>2</Subscript> doped with tin for supercapacitors

To improve the electrochemical performances of α-MnO₂ as electrode materials for supercapacitors, Sn-doped α-MnO₂ in the presence of the doping amount of 1%-4% was successfully synthesized by hydrothermal method. As-prepared α-MnO₂ presents nanorod shape and no other impurities exist. By ultraviolet-visible absorption spectroscopy, it is convinced that the band gaps of α-MnO₂ decrease with increasing Sn-doping amount. Cyclic voltammetry investigation indicates that undoped and doped α-MnO₂ all have regular capacitive response. As the scan rate enlarged, the profiles of curves gradually deviate from rectangle. Compared with undoped α-MnO₂, doped α-MnO₂ has larger specific capacitance. The specific capacitance of 3% doped α-MnO₂ reaches 241.0 F/g while undoped α-MnO₂ only has 173.0 F/g under 50 mA/ g current density in galvanostatical charge-discharge measurement. Enhanced conductivity by Sn-doping is considered to account for doped sample’s enhanced electrochemical specific capacitance.     

Forming mechanism and morphology of CaSO<Subscript>4</Subscript> · H<Subscript>2</Subscript>O by SEM-EDS and ICP

To promote the development of 3D printing materials, gypsum powders used in 3D printing were analyzed in detail through SEM-EDS and ICP. The forming mechanism and morphology of CaSO₄? χH₂O powders were analyzed and confirmed. Furthermore, the printing mechanism of gypsum powders was analyzed and discussed. According to the results of SME-EDS analysis and ICP detection, the factors affecting the forming accuracy, strength, surface quality and reliability of CaSO₄? χH₂O crystal were found in this paper. Adding a variety of additives to change the performance of calcium sulfate would be the further research.     

Pore structure of new composite adsorbent SiO<Subscript>2</Subscript>·<Emphasis Type="Italic">x</Emphasis>H<Subscript>2</Subscript>O· <Emphasis Type="Italic">y</Emphasis>CaCl<Subscript>2</Subscript> with high uptake of water from air

A new composite adsorbent SiO₂·xH₂O·yCaCl₂ which is composed of macro-porous silica gel and calcium chloride is introduced. In order to analyze its adsorption theory, adsorption and desorption isotherms, BET surface areas, pore volumes and average pore diameters of macro-porous silica gel and four composite adsorbent samples with different CaCl₂ content are measured using SEM and Asap2010 apparatus. From the adsorption isotherms, desorption isotherms and lag loops, it can be deduced that the main pore structure in macro-porous silica gel and the new composite adsorbent have two shapes: taper with one top open and taper or hyperbolic taper with both ends open. Based on the analysis of pore diameter distribution and lag loop, a sketch map showing calcium chloride filled in pore of macro-porous silica gel is presented. The adsorption isotherms at 25°C are measured. Experimental results show that the new composite adsorbent can adsorb more water than common adsorbents (macro-porous silica gel, micro-porous silica gel and synthetic zeolite 13X). In the light of the results of pore structure, adsorption isotherms and lyolysis phenomenon are analyzed.     

Magnetism regulation of (In<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>2</Subscript>O<Subscript>3</Subscript> semiconductors prepared by sol-gel method

Fe doped In₂O₃ samples (In_1−x Fe _x )₂O₃ (x=0, 0.05, 0.1, 0.2 and 0.3) on glass substrate were prepared by sol-gel method. The XRD results demonstrate that the solubility of Fe ions in In₂O₃ matrix is around 20%, above which impurity phase can be observed. The transmittance of the samples with x=0, 0.05, 0.1 and 0.2 are above 80% in the visible region while the transimittance of the glass is 90%. The transmittance curves slightly red-shifts as x increasing. All of the samples except x=0 are ferromagnetic at room temperature. The highest saturation magnetization moment is reached in the sample x=0.2 with 330 emu/cm³, and the coercive force is 169 Oe which is also the largest in our samples. The results indicate that the addition of Fe ions could tune the structure, the ferromagnetism and optical property in the In₂O₃ matrix.     

<Emphasis Type="Italic">In-situ</Emphasis> growth and photoluminescence of β-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> cone-like nanowires on the surface of Ga substrates

β-Ga₂O₃ cone-like nanowires have been in-situ grown on the surface of gallium grains and films by heating gallium substrates at 750–1000°C for 2 h in air. The controllable synthesis of β-Ga₂O₃ nanowires with different diameters and lengths was achieved by adjusting the heating temperature and time. The as-synthesized products were characterized by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the β-Ga₂O₃ nanowires are single crystalline with a monoclinic structure and have a controllable diameter and length in the range of 30–100 nm and 0.5–1.5 μm, respectively. A possible mechanism was also proposed to account for the formation of β-Ga₂O₃ cone-like nanowires. Photoluminescence spectra of the β-Ga₂O₃ nanowires obtained at different temperatures were measured at room temperature, and a strong blue photoluminescence with peaks at 430 and 460 nm and a weak red photoluminescence with peak at 713 nm were observed. The blue light emission intensity decreases with increasing the reaction temperature, however, the red light emission intensity hardly changes. The blue and red light emissions originate from the recombination of an electron on an oxygen vacancy with a hole on a gallium-oxygen vacancy pair and the nitrogen dopants, etc., respectively. Supported by the National Natural Science Foundation of China (Grant No. 20573072) and Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20060718010)     

Structures and properties of La<Subscript>0.8</Subscript>Sr<Subscript>0.2</Subscript>MnO<Subscript>3+σ</Subscript>-z SBA-15 (z=0, 1, 2, 4) perovskite catalysts

Mesoporous La_0.8Sr_0.2MnO_3+σ/z SBA-15 (z = 1, 2, 4) perovskite oxides were synthesized via hard-templating with ordered mesoporous silica SBA-15 as the template. The as-prepared samples were characterized by XRD, SEM, AFM, BET, and XPS and the catalytic activity was tested for CO oxidation. The wide-angle XRD patterns showed that La_0.8Sr_0.2MnO_3+σ perovskite was formed. The SEM and AFM analyses exhibited that La_0.8Sr_0.2MnO_3+σ by hard-templating method had much smaller particle size (18 nm) than that (40 nm) by the sol-gel method. The perovskite-type oxides La_0.8Sr_0.2MnO_3+σ/z SBA-15 (z = 1, 2, 4) also displayed a higher BET surface area from 70 to 143.7 m²/g and a disordered mesostructure from nitrogen sorption analysis, as well as a small-angle XRD pattern. Moreover, the La_0.8Sr_0.2MnO_3+σ/z SBA-15 (z = 1, 2, 4) perovskite exhibited a much higher activity in CO oxidation than the conventional La_0.8Sr_0.2MnO_3+σ perovskite. Further analysis by the means of XPS techniques indicated that the existence of high content of O_ads/O_latt species contributed to the high activity.     

Structure and infrared radiation property of Co<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> ferrites by XAFS analysis

Co_1−x Zn _x Fe₂O₄ ferrites were prepared by solid state reaction. The microstructure and performance were studied by X-ray diffraction, X-ray absorption fine-structure analysis and IRE-2 infrared radiant test. It is found that infrared radiance show a nonlinear change with x, exhibiting the infrared radiance of this material improved and the average radiance in the 8–14 μm waveband reached 0.91. The Co³⁺ and Zn²⁺ ions are found to occupy both tetrahedral and octahedral sites, and correspondingly, the fraction of Fe³⁺ ions in B-site decreases nonlinearly in ferrites. The lattice parameters are found to concern with Zn²⁺, and the activation energy deduces from crystal strain and crystal vibrate increases with content Zn²⁺. The redistribution of the Co³⁺ and Zn²⁺ ions between tetrahedral and octahedral sites is related to the providing a selective tetrahedral and octahedral sites infrared radiance of Co_1−x Zn _x Fe₂O₄ ceramics with increasing x.     

Research on the chemical adsorption precursor state of CaCl_2-NH_3 for adsorption refrigeration

Environment and energy resources are two critical global problems. Adsorption re-frigeration, as an environmental friendly and energy saving technology [1], attracts moreand more attention in recent years. Adsorption refrigeration mainly includes physical adsorption and chemical adsorp-tion. As a type of chemical adsorption working pair, CaCl2-NH3 has the prominent ad-vantage of large adsorption quantity. However, CaCl2-NH3 also has several disadvan-tages, such as performance attenuat…     

Effect of surface modification of activated carbon on its adsorption capacity for NH3

To investigate the effects of carbon surface characteristics on NH3 adsorption, coal-based and coconut shell activated carbons were modified by treatment with oxidants. The surface properties of the carbons were characterized by low temperature nitrogen sorption, by Boehm's titrations and by XPS techniques. NH3 adsorption isotherms of the original and the modified carbons were determined. The results show that the carbons were oxidized by HNO3 and (NH4)2S2O8, and that there was an increase in oxygen containing functional groups on the surface. However, the pore-size distribution of the coal-based carbons was changed after KMnO4 treatment. It was found that the NH3 adsorption capacity of the modified carbons was enhanced and that the most pronounced enhancement results from (NH4)2S2O8 oxidation. Under our experimental conditions, the capacity is positively corrected to the number of surface functional groups containing oxygen, and to the number of micro-pores. Furthermore, an empirical model of the relationship between NH3 adsorption and multiple factors on the carbon surface was fit using a complex regression method.     

氧化吸附法处理硝基苯胺生产废水

应用化学氧化、活性炭吸附工艺处理高浓度硝基苯胺生产废水（ＣＯＤＣｒ＝２０００～１７００００ｍｇ／Ｌ），处理出水的色度、ＣＯＤｃｒ、硝基苯类、苯胺类等指标均达到国家规定的废水排放标准。     

用表面修饰的活性碳吸附废水中的铜离子

活性碳去除重金属的效率取决于重金属的种类及活性碳的表面特征 .本研究将一种商品活性碳用浓硝酸修饰 ,再以氢氧化钠进一步处理 .结果显示修饰过程主要导致活性碳表面化学特征的改变而不是物理性质的变化 .测试显示修饰对活性碳表面积的影响极小 .酸碱滴定表明 ,修饰作用明显改变了活性碳对H+ 及OH-的吸附行为 .研究表明 ,溶液pH值对铜离子的吸附有显著影响 .固定缓冲pH条件下测定修饰活性的吸附能力发现 ,金属吸收容量主要取决于活性碳表面的酸碱功能团 ,因而其吸附行为可用表面酸碱理论进行解释 ,所获数据可用于建立活性碳吸附平衡和动力学模型 .     

活性炭吸附水中罗丹明B的研究

采用批量吸附实验,研究了活性炭对水中罗丹明B的吸附行为,探讨了活性炭用量、吸附时间对水中罗丹明B吸附的影响,并对活性炭再生效果进行了测定.结果表明,利用活性炭处理罗丹明B,具有处理效果好、再生容易等特点.运用Langmuir等温吸附方程对其吸附进行了描述,表明吸附属于化学吸附;用准二级吸附动力学方程和准一级吸附动力学方程对实验数据进行了回归分析,准二级吸附动力学方程能更好地描述罗丹明B在活性炭上的吸附.     

负载铁锰氧化物的活性炭除砷酸盐的性能研究

为了提高活性炭对水中的砷酸盐的去除能力,采用共沉淀法制备了2种负载铁锰氧化物的改性活性炭(FM-GAC-1,FM-GAC-2).测定了2种改性活性炭表面的零点电荷、酸碱官能团以及金属溶出量.研究2种改性活性炭去除五价砷的吸附等温线和反应动力学,考察pH值、水中共存离子对其去除五价砷的影响.结果表明,FM-GAC-1和FM-GAC-2表面的零点电荷分别为6.7、6.0;酸性官能团的含量分别为2mmol·g-1、1.667mmol·g-1,碱性官能团的含量分别为1.3mmol·g-1、2.06mmol·g-1;pH值在近中性时金属溶出率最低.在25℃时,FM-GAC-1和FM-GAC-2对五价砷的吸附容量分别为28.87mg·g-1和30.32mg·g-1,随着温度的升高,吸附容量略有下降.吸附速率采用拟二级反应动力学拟合效果最好,化学反应步骤是改性活性炭除砷的限速步骤.pH值偏酸性有利于吸附的进行,水体中SiO32-、PO43-对两者吸附砷酸盐有显著影响.     

A simplified adsorption model for water vapor adsorption on activated carbon

A simplified model was developed to describe the water vapor adsorption on activated carbon. The development of the simplified model was started from the original model proposed by DO and his co-workers. Two different kinds of carbon materials were prepared for water vapor adsorption, and the adsorption experiments were conducted at different temperatures（20-50 °C） and relative humidities（5%-99%） to test the model. It is shown that the amount of adsorbed water vapor in micropore decreases with the temperature increasing, and the water molecules form larger water clusters around the functional group as the temperature is up to a higher value. The simplified model describes reasonably well for all the experimental data. According to the fitted values, the parameters of simplified model were represented by the temperature and then the model was used to calculate the water vapor adsorption amount at 25 °C and 35 °C. The results show that the model can get relatively accurate values to calculate the water vapor adsorption on activated carbon.     

活性炭对钌基氨合成催化剂活性的影响

研究了不同活性炭的表面性质与钌基氨合成催化剂活性的关系.以不同种类的活性炭为载体制备的钌基催化剂,其活性有很大的不同.活性炭的表面结构和表面化学性质均会对催化剂性能产生重要影响.研究发现催化剂活性与活性炭比表面积,总孔容之间并没有直接的依赖关系,而活性炭载体的灰分,pH值及中孔的孔容对催化剂活性影响较大.对活性炭进行适当的氧化改性处理可以提高催化剂的活性.促进剂与载体及活性组分之间存在强相互作用,当促进剂的含量改变时钌基催化剂的活性也产生明显变化,并且研究表明适当增大助剂K的含量可以提高催化剂的低温活性.     

活性炭吸附／Fenton试剂氧化法处理造纸厂污冷凝水的研究

采用活性炭吸附过滤／Ｆｅｎｔｏｎ试剂氧化法,对硫酸盐木浆造纸厂污冷凝水中的难降解有机物的去除效果进行了研究。并对Ｆｅｎｔｏｎ试剂氧化法对ＣＯＤ去除率的各种实验条件及影响因素进行了详细研究。结果表明,当Ｈ２Ｏ２与Ｆｅ＾２＋的社量比在８：１－１０：１之间时,ｐＨ３－５,反应时间为１ｈ,Ｈ２Ｏ２投量为６．６ｍＬ／Ｌ污冷凝水时,即去除每ｍｇ／Ｌ ＣＯＤ需要Ｈ２Ｏ２ ０．２ｍｍｏｌ,Ｆｅ＾２＋０．０２ｍｍｏ