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…     

Removal of aqueous Ni(Ⅱ) with carbonized leaf powder: Kinetics and equilibrium

Nickel is a heavy metal which has the potential threaten to human's health and attracts public concern recently. The carbonized leaf powder is expected as suitable adsorbent for Ni(II) removal became of the composition of some beneficial groups. In this work, carbonized leaf powder was evaluated for its adsorption performance towards Ni(II). According to the results, adsorbent component, dosage, initial solute concentration, solution p H, temperature and contact time can significantly affect the efficiency of Ni(II) removal. Sips model fits the test results best, and the adsorption capacity towards Ni(II) is determined around 37.62 mg/g. The thermodynamic behaviors reveal the endothermic and spontaneous nature of the adsorption. The free adsorption energy(fluctuate around 8 k J/mol) predicted by D-R model indicates that the adsorption capacity originated from both physical and chemical adsorption. Room temperature(15-25 °C) is suitable for Ni(II) removal as well as low energy consumption for temperature enhancement. Further conclusions about the mechanism of chemical adsorption are obtained through analysis of the FT-IR test and XRD spectra, which indicates that the adsorption process occurs predominantly between amine, carbonate, phosphate and nickel ions.     

Oxygen adsorption on pyrite （100） surface by density functional theory

Pyrite (FeS2) bulk and (100) surface properties and the oxygen adsorption on the surface were studiedby using density functional theory methods. The results show that in the formation of FeS2 (100) surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe^2 and S^2- have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.     

Equilibrium and kinetics of adsorption of Ca(Ⅱ) ions onto KCTS and HKCTS

The adsorption of Ca(Ⅱ) ions from aqueous solution by chitosan α-ketoglutaric acid(KCTS) and hydroxamated chitosan α-ketoglutaric acid(HKCTS) was studied in a batch adsorption system.The Langmuir and Freundlich adsorption models were applied to describing the equilibrium isotherms,and isotherm constants were determined.The kinetics of the adsorption with respect to the initial Ca(Ⅱ) ions concentration,temperature and pH was investigated.The pseudo-first-order and second-order kinetic models were used to describe the kinetic data and the rate constants were evaluated.The results show that the experimental data fit well to the Langmuir isotherms with a high correlation coefficient(R2).The pseudo-second-order rate expression provides the best fitting kinetic model.The pseudo second-order kinetic model is indicated with the activation energy of 26.22 kJ/mol and 6.16 kJ/mol for KCTS and HKCTS,respectively.It is suggested that the overall rate of adsorption of Ca(Ⅱ) ions is likely to be controlled by the chemical process.     

Adsorption behavior of Pb^2＋ and Cd^2＋ ions on bauxite flotation tailings

The adsorption behavior of Pb^2＋ and Cd^2＋ ions on bauxite flotation tailings was investigated to demonstrate the adsorptivity of the bauxite flotation tailings. The adsorption percentage of Pb^2＋ and Cd^2＋ ions as a function of adsorbent dosage, solution pH value and shaking time were determined by batch experiments. The maximum adsorption percentage of 99.93% for Pb^2＋ ions and 99.75% for Cd^2＋ ions were obtained by using bauxite flotation tailings as adsorbent. The methods, such as zeta potentials, specific surface area measurements and the analysis of adsorption kinetics, were introduced to analyze the adsorption mechanisms of the Pb^2＋ ions on bauxite flotation tailings. The isoelectric point of bauxite flotation tailings shifts from 3.6 to 5.6 in the presence of Pb^2＋ ions. The specific surface area of bauxite flotation tailings changes from 12.57 to 20.63 m^2/g after the adsorption of Pb^2＋ ions. These results indicate that a specific adsorption of the cation species happens on the surface of bauxite flotation tailings. Adsorption data of Pb^2＋ ions on the surface of bauxite flotation tailings can be well described by Langmuir model, and the pseudo-second-order kinetic model provides the best correlation for the adsorption data of Pb^2＋ and Cd^2＋ ions on bauxite flotation tailings.     

Fabrication and adsorption property of novel adsorbent for potential application to wastewater with Fe（Ⅲ） ions

The spherical macroporous cellulose（SMC） was fabricated using medical absorbent cotton as raw material and nano CaCO3 as porogenic agents.And then,the phenylglycine was grafted onto the SMC to obtain the novel spherical macroporous cellulose derivative adsorbent（PSMC）.FT-IR and scanning electron microscope（SEM） were employed to characterize the adsorbents and Fe3＋ ions served as model solute to evaluate the adsorption property of the adsorbents.The experimental results show that the amount of porogenic agents and the value of pH have obvious influence on adsorption capacity of the adsorbents.The data of adsorption kinetic and isotherm display that the adsorbents possess excellent equilibrium adsorption capacity（348.94 mg/g） and have a bright prospect and considerable potential in the treatment of Fe3＋ ions in wastewater.     

First-principles study on adsorption of Au atom on hydroxylated SiO<Subscript>2</Subscript> surface

Adsorption of single gold (Au) atom at three kinds of sites (hollow, bridge and top) on the hydroxylated β-cristobalite SiO2 (1 1 1) surface was studied using the first-principles calculations with general gradient approximation (GGA). The results of adsorption energies and density of electronic states (DOS) suggest that the hollow and bridge sites have the basically equal capability of binding Au, while the ability of the Top site is weaker. Two new energy levels emerge after the adsorption at all sites; i...     

Pore structure of SWNTs with high hydrogen storage capacity

This paper reveals, by analyses of nitrogen cryo-adsorption isotherm, the energetic and structural heterogeneity of single-walled carbon nanotubes (SWNTs) which has a high hydrogen storage capacity. It was found that SWNTs had manifold pore structures and distributed surface energy. By comparison of the pore structures and energy distributions of SWNTs before and after hydrogen adsorption, it is preliminarily indicated that hydrogen adsorption occurred in micropores and mesopores with smaller diameter, and that the pores of different diameters determined different hydrogen adsorption processes and underwent different structure changes during hydrogen adsorption.     

Microstructure and Characterization of Capric-stearic Acid/Modified Expanded Vermiculite Thermal Storage Composites

In order to improve the thermal storage capacity of expanded vermiculite(EV) based formstable composite PCM(FS-PCM) via organic modification of EV, first, EV was modified with a sodium stearate(Na St) as surface modifier, and organic EV(OEV) with hydrophobicity and higher adsorption capacity for fatty acid was obtained. A novel capric-stearic acid eutectic(CA-SA)/OEV FS-PCM with high thermal storage capacity was then developed. OEV and CA-SA/OEV were characterized by scanning electron microscopy(SEM), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), differential scanning calorimetry(DSC), thermal gravimetry(TG), and thermal cycling test. Results showed that OEV has obvious hydrophobicity and a higher adsorption capacity for fatty acid. Its adsorption ratio has increased by 48.71% compared with that of EV. CA-SA/OEV possesses high thermal storage density(112.52 J/g), suitable melting temperature(20.49 ℃), good chemical compatibility, excellent thermal stability and reliability, indicating great application potential for building energy efficiency. Moreover, organic modification of inorganic matrix may offer novel options for improving its adsorption capacity for organic PCMs and increasing heat storage capacity of corresponding FS-PCMs.     

Influences of soluble salts on adsorption properties of polycarboxylate superplasticizers

Polycarboxylate(PC) superplasticizers with different chemical structures were synthesized through free radical co-polymerization reaction.A total organic carbon analyzer was used to investigate adsorption behaviors of PCs,and to evaluate influences of soluble salts on absorption properties of PCs.It is found that adsorption ratios of PCs on cement particles decrease greatly with the addition of Na2SO4;the adsorption ratio of ethers PC with Hydroxyethyl methacrylate(HEMA) group first increases then decreases with the addition of NaCl;the adsorption ratio of esters PC with short side chains first decreases then increases,while the adsorption ratio of ethers PC with HEMA group decreases with the addition of CaCl2;the adsorption ratio of esters PC with short side chains decreases with the addition of Ca(NO3)2;AlCl3 causes the decrease of the adsorption ratio of ethers PC with HEMA group.     

Adsorption performances and refrigeration application of adsorption working pair of CaCl<Subscript>2</Subscript>−NH<Subscript>3</Subscript>

The adsorption performance of CaCl₂−NH₃ is studied under the condition of different expansion spaces for adsorbent, and the relationships between adsorption performance of CaCl₂−NH₃ and the phenomena of swelling and agglomeration during adsorption are researched. It is found that the performance stability is related to the ratio of expansion space to the volume of adsorbent r _as, and the performance attenuation is serious in the case of large r _as. Severe adsorption hysteresis exists in the process of adsorption and desorption at the same evaporating and condensing temperatures, which is related to the stability constant of chemical reaction. This phenomenon cannot be explained by the theory of physical adsorption. Moderate agglomeration will be beneficial to the formation of ammoniate complex; the magnitude of expansion space will affect adsorption performance. Analysis shows that the activated energy needed in the process of adsorption for the sample with r _as. of 2∶1 is less than that for the sample with r _as of 3∶1. The refrigeration performance of CaCl₂−NH₃ is predicted from experiments. The cooling capacity of one adsorption cycle is about 945.4 kJ/kg for the adsorbent with an r _as of 2∶1 at the evaporating temperature of 0°C.     

离子交换改性斜发沸石用于分离性能研究N2/CH4

抽放煤层气的主要成分为氮气和甲烷,采用以N2为强吸附组分的天然斜发沸石进行变压吸附分离(PSA),CH4成为塔顶产品,其回收率和纯度会大大提高.首先对4种国内不同地区的斜发沸石进行筛选,结果表明1#斜发沸石氮气吸附量大于甲烷,为氮气选择性吸附剂.为了进一步提高1#斜发沸石的氮气选择性能,对其进行离子交换改性研究,发现在室温下交换3次的Na-Cp-1分离效果最好,氮气/甲烷分离因子达5.48,是非常好的氮选择性吸附剂;而Li+、K+、NH4+、Ca2+、Mg2+、Sr2+离子交换后斜发沸石对N2和CH4的吸附差异较小.     

The theoretical study of O<Subscript>2</Subscript> adsorption on NiTi (100) and (110) surfaces

The discrete variational Xa method (DV-Xα) within the framework of density-functional theory was applied to study O₂ molecule adsorption on NiTi (100) and (110) surfaces. The bond order and charge distribution between Ti and O atoms for two possible O₂ molecule adsorption ways on NiTi (100) and (110) surfaces were calculated. It is found that the adsorption way for O−O bond perpendicular to NiTi surface is preferred to that for O−O bond parallel to NiTi surface, and O₂ molecule only interacted with one nearest surface titanium atom during the adsorption process. Mulliken population and the partial density of state analysis show that the interaction between Ti and O atoms is mainly donated by O 2p and Ti 4s electrons on NiTi(110) surface, O 2p and Ti 4s, 4p electrons on NiTi(100) surface, respectively. The total density of state analysis shows that NiTi(100) surface is more favorable for O₂ molecule adsorption. HUA Ying-jie: Born in 1966. Funded by the National Natural Science Foundation of China (No. 50081001)     

Study on H atoms diffusion and adsorption properties of MgH<Subscript>2</Subscript>-V systems

Based on experimental results that VH_0.81/MgH₂ interface was found during the process of mechanically milling MgH₂+5at.%V nanocomposite, H atoms diffusion and adsorption properties of MgH₂-V systems have been investigated by using a first-principles plane-wave pseudopotential method based on the density functional theory. The results are as follows. When VH/MgH₂ interface is formed due to V alloying MgH₂ phase, the vacancy formed by H atoms near VH phase region is more stable than that without V alloying, while vacancy near MgH₂ phase region is less stable than that without V alloying. During the process of H atoms diffusion after V alloying, the max migration barrier energy of H atoms in MgH₂-V systems is reduced compared with that of MgH₂ phase, which means that H atoms diffuse easily. When H diffuses into VH from MgH₂ across VH/MgH₂ interface, among three substitutions such as the replacement of H for V vacancy, or interstitial site or V atoms, the replacement of H for V vacancy has the strongest diffusion ability, next interstitial site, and finally V atoms site. As far as H adsorbed on different surfaces of VH phase is concerned, physical adsorption is carried out more easily than chemical adsorption, and the behavior of H atoms adsorbed on the surface near VH phase region can be found more easily than that near MgH₂ phase region. Supported by the Ministry of Science and Technology of China (Grant No. 2006CB605104) and the National Natural Science Foundation of China (Grant No. 50771044)     

分子印迹型CO_2吸附剂的改性及吸附性能研究

基于前期研究工作,通过同时提高模板分子比例和溶剂中添加甲苯的方法,改性分子印迹吸附剂,并通过N2吸附和红外光谱分析两种实验手段,对吸附剂的孔结构和表面官能团的情况进行了表征,对吸附剂改性前后的CO2的吸附性能进行了对比。实验结果表明,同时提高模板分子比例和添加甲苯溶剂的方法,增加了吸附剂的比表面积和表面胺基团密度,提高了吸附剂的吸附容量。本文同时研究了温度对吸附剂CO2的吸附性能的影响,结果表明,随着温度的增加CO2的吸附容量明显降低。     

固胺负载SBA-15的石墨烯改性及其CO2吸附性能

为了提高固胺负载SBA-15的CO₂吸附性能及稳定性,推进其在燃烧后CO₂捕集中的实际应用,采用湿法浸渍制备新型石墨烯掺杂超支链聚合物（HBP）负载SBA-15（G/SBA-15/HBP）固胺负载吸附剂用于CO₂捕集. 通过SEM、TEM、N₂吸附、XRD、FTIR对吸附剂的微观结构和化学组成进行表征,研究分析HBP负载量、吸附温度和脱附温度对CO₂吸附性能的影响并优化反应条件,探讨石墨烯改性前、后吸附剂的热稳定性和循环性能. 结果表明,当HBP负载量达到50%时,G/SBA-15/HBP的CO₂吸附量为1.50 mmol/g,相较传统SBA-15/HBP提升了51.51%. 石墨烯掺杂能减少颗粒团聚,有利于气体扩散;增加载体12%比表面积及31%孔隙容积,有利于负载HBP的均匀分散,暴露更多的吸附位点. 石墨烯掺杂提升了固胺负载吸附剂的热稳定性,提高了吸附剂的使用寿命及循环稳定性.     

Chemieal Strueturcs and Adsorptive Behaviors of Superplastieizers on β-C2S

The chemical structures of four types of superplasticizers （SPs） and their adsorptive behaviors on β-C2S were investigated. The adsorption properties of SPs on β-C2S were measured and the relationship between the adsorption quantity and the specific surface of β-C2S was analyzed. The experimental results show that the adsorption quantity increases with the surface area increase of β-C2S, but the adsorption quantity per surface area is similar, which means that the main adsorbent is β-C2S itself. Polycarboxylic ester （PCE） showed the highest adsorption amount on β-C2S, followed by β-naphthalene sulfonates （NSF） and formaldehyde-acetone condensates sulfonates （FAS）, amino sulphonate （AS） showed the least adsorption amount on β-C2S. PCE affected the surface potential of β-C2S particles in water differently in comparison with other types of SPs. The adsorption capacity of SPs on β-C2S is determined by factors such as molecular structure, functional groups and molecular weight of SPs.     

Dispersing and doping of BaTiO<Subscript>3</Subscript> powder by adsorption

Dispersing and doping of BaTiO3 powder by adsorption method were investigated. Ultrafine BaTiO3 powders were dispersed in the aqueous with ammoniumized citrate （NHa-CA） or ammoniumized citric lanthanum chelate （NH4-La-CA） as dispersant by ultrasonic bath. Better dispersion of BaTiO3 slurry was obtained in the aqueous with NH4-La-CA than that of NH4-CA when the mass ratio of citric acid （CA） to BaTiO3 was less than 0,007. The pH value hardly affects the dispersion property of BaTiO3 suspension dispersed by NH4-La-CA. BaTiO3 powder could be well dispersed （median size D50=0.45 μm） and also doped with high uniformity of added components by adsorbing citric acid chelate on surface. Compared with solid mixing, better microstructure and properties of La/Mn codoped ceramics were obtained by adsorption method.     

Preparation and adsorption property of hydrophobic SiO<Subscript>2</Subscript> aerogels modified by methyl triethoxysilane

The hydrophobic SiO2 aerogels were prepared by in-situ polymerization sol-gel method and supercritical drying of ethanol method with tetraethylorthosilicate(TEOS) as silica source, methyl triethoxysilane (MTMS) as modifier, ethanol as solvent. Moreover, the structure and adsorption property of SiO2 aerogels were also studied. As results, the surface area of SiO2 aerogels was 863.59 m2/g, the pore volume was 3.57 cm3/g, and the contact angle was 150 °. Adsorption intensity of silica aerogels for organic liquid (alkanes, benzene compounds, and nitro-compounds) is bigger than that of activated carbon. The mass of the liquid absorbed increased linearly with the surface tension of the liquid. The lower surface tension and boiling point are, the shorter desorption time is. After regenerating 10 times, nitromethane regeneration rate remain the same, and almost more than 94%. So SiO2 aerogels have good absorption and regeneration property.