Kinetics and thermodynamics of cadmium ion removal by adsorption onto nano zerovalent iron particles

Nano zerovalent iron (nZVI) is an effective adsorbent for removing various organic and inorganic contaminants. In this study, nZVI particles were used to investigate the removal of Cd(2+) in the concentration range of 25-450 mg L(-1). The effect of temperature on kinetics and equilibrium of cadmium sorption on nZVI particles was thoroughly examined. Consistent with an endothermic reaction, an increase in the temperature resulted in increasing cadmium adsorption rate. The adsorption kinetics well fitted using a pseudo second-order kinetic model. The calculated activation energy for adsorption was 54.8 kJ mol(-1), indicating the adsorption process to be chemisorption. The intraparticle diffusion model described that the intraparticle diffusion was not the only rate-limiting step. The adsorption isotherm data could be well described by the Langmuir as well as Temkin equations. The maximum adsorption capacity of nZVI for Cd(2+) was found to be 769.2 mg g(-1) at 297 K. Thermodynamic parameters (i.e., change in the free energy (ΔG(o)), the enthalpy (ΔH(o)), and the entropy (ΔS(o))) were also evaluated. The overall adsorption process was endothermic and spontaneous in nature. EDX analysis indicated the presence of cadmium ions on the nZVI surface. These results suggest that nZVI could be employed as an efficient adsorbent for the removal of cadmium from contaminated water sources.     

Fabrication of hierarchical structured superhydrophobic Copper surface by in-situ method with micro/nano scaled particles

Chlorofluoro silane (CFSi) decorated Copper doped SiO₂ coated Copper surface was synthesized by an in-situ method and characterized by various analytical tools like Fourier Transform Infrared (FTIR) Spectroscopy, UV-Visible spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and contact angle measurements. In the present investigation, the bulk Copper plate was served as a resource material for the generation of Copper with simultaneous chemical etching reaction in an aqueous acidic and alcoholic medium. The modified Copper surface has a contact angle of 152°.     

Modeling,processing, and characterization of exfoliated graphite nanoplatelet-nylon 6 composite fibers

We present theoretical and experimental studies on the effects of platelet-like filler orientation on the mechanical properties of melt-spun exfoliated graphite nanoplatelet(xGnP)-nylon 6(PA6) composite fibers. In numerical studies, the Mori–Tanaka micromechanics model was employed to formulate analytical models to predict the mechanical properties of xGnP-PA6 composite fibers with varying xGnP orientations in a three-dimensional spatial domain. Simulation results showed that the predicted properties of xGnP-PA6 composite fibers were highly affected by xGnP orientation and were correlated with the measured properties of composite fibers treated with varying draw ratios. The tensile moduli of composite fibers at varying xGnP contents showed significant improvements, which is attributed to the drawing-induced alignment of PA6 molecular chains as well as the alignment of xGnPs. Both as-received and acid-treated xGnPs were incorporated in PA6, and mechanical test results suggested that acid-treated xGnPs provide stronger interfacial bonding with PA6.     

Material and bond properties of ultra high performance fiber reinforced concrete with micro steel fibers

For investigating the effect of fiber content on the material and interfacial bond properties of ultra high performance fiber reinforced concrete (UHPFRC), four different volume ratios of micro steel fibers (V_f = 1%, 2%, 3%, and 4%) were used within an identical mortar matrix. Test results showed that 3% steel fiber by volume yielded the best performance in terms of compressive strength, elastic modulus, shrinkage behavior, and interfacial bond strength. These parameters improved as the fiber content was increased up to 3 vol.%. Flexural behaviors such as flexural strength, deflection, and crack mouth opening displacement at peak load had pseudo-linear relationships with the fiber content. Through inverse analysis, it was shown that fracture parameters including cohesive stress and fracture energy are significantly influenced by the fiber content: higher cohesive stress and fracture energy were achieved with higher fiber content. The analytical models for the ascending branch of bond stress-slip response suggested in the literature were considered for UHPFRC, and appropriate parameters were derived from the present test data.     

Characterization and tensile strength of HPC-PEO composite fibers produced by electrospinning

Hydroxypropylcellulose (HPC) and polyethylene oxide (PEO) were dissolved in water in order to be electrospun. The electrospun membranes showed porous structure with fibers having diameter of 255 ± 65 nm. Synthesized silver nanoparticles of 5-8 nm were embedded into the HPC/PEO matrix to improve the strength. It was seen that the embedding of silver particles into the polymer matrix improved the membrane strength ∼ 4 times.     

ZnO纳米材料改性油漆涂层的制备及其浸润性的研究

采用水浴法生长出蒲公英状的纳米ZnO材料,并将其与油漆混合,制备出改良油漆涂层.分别用场发射扫描电子显微镜(FE-SEM)和接触角测量仪对其表面形貌和浸润性进行了表征.实验结果表明,加入ZnO材料后,不仅增加了油漆涂层的表面粗糙度,油漆涂层的疏水性能也得到显著改善,水滴在油漆涂层上的接触角由改良前的95°增加到改良后的...     

Physical and mechanical properties of SEBS/polypropylene nanocomposites reinforced by nano CaCO3

In present study, styrene‐b‐(ethylene‐co‐butylenes)‐b‐styrene triblock copolymer (SEBS) and polypropylene (PP) are prepared. This mixing is followed by adding 3, 5 and 10 wt% of nano CaCO₃. The morphology and thermal behavior of PP/SEBS/nano‐CaCO₃ compounds are characterized by different methods. Scanning electron microscopy micrographs of cryo‐fractured PP/SEBS/nano‐CaCO₃ nanocomposites show that with increasing nano‐CaCO₃ loading, the aggregation becomes worse. However, followed by adding 5 wt% nano‐CaCO₃ into PP/SEBS nanocomposites, nano‐CaCO₃ is homogeneously dispersed in PP matrix. The photomicrograph of transmission electron microscopy confirms that SEBS/PP/nano‐CaCO₃ nanocomposites are formed, as low aggregations of calcium carbonate were well‐dispersed in polymer matrix. With a rise in nano‐filler content, the tensile and impact strength of PP/SEBS/CaCO₃ nanocomposite are fixed while the elastic modulus of PP/SEBS nanocomposites increases followed by adding nano‐CaCO₃ to polymer blend, which could be due to the acceptable nano‐CaCO₃ dispersion quality.     

有机硅改性丙烯酸树脂乳液的合成及性能研究

采用乳液聚合法,并以种子乳液法分步加料方式,将一定比例丙烯酸酯单体、自制的有机硅大分子单体进行自由基聚合,得到有机硅改性丙烯酸树脂乳液.利用单因素实验和5因素4水平正交实验优化出最佳工艺参数:MM用量为1.2%,有机硅预聚体的用量为9%,单体配比为0.76,异丙醇用量为1.5%,可获得高稳定性乳液,成膜各项性能提高.     

水分散多异氰酸酯交联苯乙烯-丙烯酸酯树脂的制备及性能

以苯乙烯、丙烯酸丁酯、N-羟甲基丙烯酰胺、丙烯酰胺为原料,用聚乙烯醇(PVA)作为胶体保护剂,采用无皂乳液聚合方式,制备苯乙烯-丙烯酸酯树脂乳液;以HDI三聚体和聚乙二醇单甲醚(MPEG500)为主要原料制备水可分散聚异氰酸酯.苯乙烯-丙烯酸酯树脂乳液与亲水改性聚异氰酸酯复合,得到水分散多异氰酸酯交联改性的苯乙烯-丙烯...     

Isotherm, thermodynamic, kinetics and adsorption mechanism studies of methyl orange by surfactant modified silkworm exuviae

This paper reports on the development of organo-modified silkworm exuviae (MSE) adsorbent prepared by using hexadecyltrimethylammonium bromide (HDTMAB) for removing methyl orange (MO), a model anionic dye, from aqueous solution. The natural and modified samples were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and Fourier transform infrared spectroscopy (FT-IR). Batch adsorption experiments were carried out to remove MO from its aqueous solutions using SE and MSE. It was observed that the adsorption capacity of MSE is 5-6 times of SE. The different parameters effecting on the adsorption capacity such as pH of the solution, initial dye concentration, temperature and contact time have been investigated. Analysis of adsorption results obtained at different temperatures showed that the adsorption pattern on the MSE can be described perfectly with Langmuir isotherm model compared with Freundlich and Dubinin-Radushkevich (D-R) isotherm models, and the characteristic parameters for each adsorption isotherm were also determined. The adsorption process has been found exothermic in nature and thermodynamic parameters have been calculated. The adsorption kinetic followed the pseudo-second order kinetic model. The results of FT-IR, EDS and desorption studies all suggest that methyl orange adsorption onto the MSE should be mainly controlled by the hydrophobic interaction mechanism, along with a considerable contribution of the anionic exchange mechanism. The results indicate that HDTMAB-modified silkworm exuviae could be employed as low-cost material for the removal of methyl orange anionic dye from wastewater.     

电火花加工制备铜基微纳层次结构及其疏水性能

利用电火花成型加工技术制备铜基微纳层次结构疏水表面,该微纳层次结构主要由微纳孔洞、熔珠、重熔区和热应力裂纹等微观结构组成,考察了不同脉宽参数对微纳层次结构疏水性的影响。结果表明:随着脉宽的增大,微纳层次结构中微纳孔洞数量增加,各种微观结构的层次分布程度增强,增大“气垫”效应区域,可存储更多的空气在其表面,提高了微纳层次结构的疏水性。固-液界面所占面积分数(f sl)减小,水滴和表面孔洞中的“气垫”接触面积增大,使得微纳层次结构对水滴的物理吸附作用减弱。微纳层次结构接触角可增至(144.7±2.1)°,接触角滞后性范围为(8.46±3.3)°^14.10±1.2°。     

交联改性苯乙烯-丙烯酸酯树脂纸张表面施胶增强剂的制备及应用

以苯乙烯、丙烯酸丁IR,N-羟甲基丙烯酰胺、丙烯酰胺为原料,用聚乙烯醇(PVA)作为胶体保护剂,采用无皂乳液聚合方式,制备苯乙烯-丙烯酸酯树脂乳液.同时以HDI三聚体与聚乙二醇单甲醚500(MPEG 500)为主要原料制备水分散聚异氛酸酯交联剂.用苯乙烯一丙烯酸酯树脂乳液与亲水改性聚异氛酸酯复合,制备纸张表面施胶增强剂...     

Enhancement of conductivity stability of polypyrrole films modified by valence copper and polyethylene oxide in an oxygen atmosphere

The degradations of polypyrrole (PPy)-based films in conductivity are examined in an oxygen atmosphere for 50 days. The results reveal that polymerization potential, solvents used in polymerization, modification of PPy with valence Cu, and introduction of polyethylene oxide (PEO) into PPy influence the conductivities of PPy films and their corresponding stabilities significantly. Pure PPy, prepared in water at an over-oxidized potential, shows a serious decrease in conductivity. However, valence Cu-modified PPy and PEO-modified PPy, resulting in an electron transfer from Cu to N⁺ of PPy and a more compact, dense surface and hydrogen bonds forming, respectively, behave more stable. The changes of surface mean roughness before and after aging are quantitatively measured via atomic force microscopy (AFM) analysis. Meanwhile, SERS experiments provide a deeper insight into the aging mechanism of PPy in conductivity.     

Effect of silica particles modified by in-situ and ex-situ methods on the reinforcement of silicone rubber

In-situ and ex-situ methods were applied to modify silica particles in order to investigate their effects on the reinforcement of silicone rubber. Surface area and pore analyzer, laser particle size analyzer, Fourier-transform infrared spectroscopy (FTIR), contact-angle instrument, and transmission electron microscope (TEM) were utilized to investigate the structure and properties of the modified silica particles. Dynamic mechanical thermal analyzer (DMTA) was employed to characterize the vulcanizing behavior and mechanical properties of the composites. Thermogravimetric analysis (TGA) was performed to test the thermal stability of the composites. FTIR and contact angle analysis indicated that silica particles were successfully modified by these two methods. The BET surface area and TEM results reflected that in-situ modification was more beneficial to preparing silica particles with irregular shape and higher BET surface area in comparison with ex-situ modification. The DMTA and TGA data revealed that compared with ex-situ modification, the in-situ modification produced positive influence on the reinforcement of silicone rubber.     

Friction and wear studies of polyimide composites filled with short carbon fibers and graphite and micro SiO2

Polyimide (PI) composites filled with short carbon fibers (SCFs), micro SiO₂, and graphite (Gr) particles were prepared by means of hot press molding technique. The friction and wear properties of the resulting composites sliding against GCr15 steel were investigated on a model ring-on-block test rig. Experimental results revealed that single incorporation of graphite and SCF significantly improve the tribological properties of the PI composites, but micro SiO₂ was harmful to the improvement of the friction and wear behavior of the PI composite. It is found that a combinative addition of Gr, SCF and micro SiO₂ was the most effective in improving the friction-reducing and anti-wear abilities of the PI composites. Research results also show that the filled PI composites exhibited better tribological properties under higher PV-product.     

Evolution and fractal growth of micro/nano structured wires of ruthenium synthesised by microwave irradiation of ruthenium dioxide

Ruthenium metal wires up to 3 mm long and 10-20 µm diameter, were produced in 20-30 s from anhydrous ruthenium dioxide by irradiation at 600 W in a microwave oven. The irradiation led to decomposition of ruthenium dioxide powder to ruthenium metal particles that sintered together along microwave field lines producing wires. Irradiation over 90 s produced larger features of metallic ruthenium with evidence of molten metal having been present. The evolution of wire growth proceeded in a fractal manner with self-similarity existing from the smallest to the largest wires.     

Kinetic studies of adsorption of Pb(II), Cr(III) and Cu(II) from aqueous solution by sawdust and modified peanut husk

Sawdust and modified peanut husk were used as adsorbents to remove Pb(II), Cr(III) and Cu(II) from aqueous solution. Results of kinetic experiments demonstrated that the adsorption was effective and rapid. Three different kinds of kinetic models (i.e., intraparticular diffusion model, Lagergren-first-order and second-order equations) were used to investigate the adsorption mechanisms. The adsorption of heavy metals on sawdust and modified peanut husk is not an intraparticular diffusion control. The kinetic adsorption data can be described by the second-order equation and the adsorption might be a rate-limiting control. The suitability of the adsorbent was tested by fitting the adsorption data with Langmuir and Freundlich isotherms, which gave good fits with both isotherms.     

Surface properties and interfacial adhesion studies of aramid fibres modified by gas plasmas

The surface of aramid (Kevlar 49) fibre was modified by NH₃, O₂ or H₂O plasmas in order to improve the adhesion to epoxy resin. Electron spectroscopy for chemical analysis (ESCA) and static secondary ion mass spectroscopy (SSIMS) were used to identify the chemical compositions and functional groups of the plasma-treated fibre surface, respectively. The surface topography and mechanical properties of plasma-treated fibres were also investigated. After plasma treatments, the interfacial shear strength (IFSS) of aramid-fibre/epoxy-resin composites, as measured by the microbond pull-out technique, was markedly improved (43–83% improvement) and the fibre strength was only little affected (less than 10% loss). Significant improvement in the IFSS principally resulted from forming the covalent bonds between the newly reactive functionalities at the modified fibre surfaces and the epoxides of the resin.     

Physical properties of carbon nanotubes radiated by proton beams: Gas adsorption and electron microscopy studies

Single walled carbon nanotues (SWCNTs) of high purity and multi walled carbon nanotubes (MWCNTs) were radiated by high energies of proton and electron beams. The surface physical properties were examined by XRD and TEM for both irradiated and non-radiated samples to compare the effect of radiation. The possible changes of surface characteristics were investigated by isotherm gas adsorption technique using Ar which can probe the local structure in an order of atomic scale. A series of Ar gas adsorption results measured below 77 K revealed significant changes in surface properties of carbon nanotubes by the bombardment of proton beams, which may induce the local surface defects. It is speculated that reactions on carbon nanotubes radiated by beams were led by kinetic energy transfer of the bombardments.