Biosorption kinetics, thermodynamics and isosteric heat of sorption of Cu(II) onto Tamarindus indica seed powder

Biosorption of Cu(II) by Tamarindus indica seed powder (TSP) was investigated as a function of temperature in a batch system. The Cu(II) biosorption potential of TSP increased with increasing temperature. The rate of the biosorption process followed pseudo second-order kinetics while the sorption equilibrium data well fitted to the Langmuir and Freundlich isotherm models. The maximum monolayer Cu(II) biosorption capacity increased from 82.97 mg g(-1) at 303 K to 133.24 mg g(-1) at 333 K. Thermodynamic study showed spontaneous and endothermic nature of the sorption process. Isosteric heat of sorption, determined using the Clausius-Clapeyron equation increased with increase in surface loading showing its strong dependence on surface coverage. The biosorbent was characterized by scanning electron microscopy (SEM), surface area and porosity analyzer, X-ray diffraction (XRD) spectrum and Fourier transform infrared (FTIR) spectroscopy. The results of FTIR analysis of unloaded and Cu(II)-loaded TSP revealed that -NH(2), -OH, -C=O and C-O functional groups on the biosorbent surface were involved in the biosorption process. The present study suggests that TSP can be used as a potential, alternative, low-cost biosorbent for removal of Cu(II) ions from aqueous media.     

多功能热管型二级吸附制冷的循环特性研究

设计了一台以氯化钙/活性炭复合吸附剂和氨作为吸附工质对的多功能热管型吸附制冷机组,采用一种新型的基于二次回热的二级循环方式来降低驱动热源的温度梯度,吸附床的加热解吸、冷却吸附及回热过程均由无外加驱动力的多功能热管工作完成.研究结果表明:当解吸温度为103℃及冷却水温度为30℃时,回热型二级循环相对传统二级循环可显著提高机组的工作性能,制冷系数COP及单位质量吸附剂制冷功率SCP提高幅度均在23%以上;相对单级循环,二级吸附循环的最大优点在于能有效利用更低品位的余热和可再生能源作为驱动热源进行制冷,吸附制冷技术在低温热源场合的应用提供了有效途径.     

Cobalt sorption properties of MgO prepared by solution combustion

Water effect on the combustion preparation of MgO is presented. The obtained materials are characterized through their specific surface area, morphology, particle shape, fractal dimension and Co²⁺ sorption. The surface fractal dimension of the combustion prepared sample was 2.0 but in those where water was included it decreased to 1.8. In the sample prepared by calcination it was 2.3. A linear correlation between the fractal dimension and Co²⁺ sorption was found.     

Self-assembly in ternary systems: cross-linked polyelectrolyte,linear polyelectrolyte and surfactant

The competitive interactions in ternary systems consisting of a slightly cross-linked polyelectrolyte hydrogel and the mixture of linear polyelectrolyte and micelle forming surfactant both oppositely charged relative to the polyelectrolyte network were studied. It was shown that the equilibrium in the competitive reactions depends on the linear polyion charge density and the length of the surfactant aliphatic radical. Dependency on these characteristics the interpolyelectrolyte complex formed by cross-linked and linear polyelectrolytes can uptake surfactant ions from water solution transforming into the cross-linked polyelectrolyte-surfactant complex and releasing the linear polyelectrolyte or vice versa. The ternary systems of this kind are perspective to design the novel family of delivery constructs.     

Diffusion of Organic Vapors in Materials for Gas Sensing Application

Mass-variation measurements were carried out on carbon black (CB)-poly(vinyl chloride) (PVC) composite film with 40% by weight of di(2-ethylhexyl)-phthalate (DOP), cast on resonant piezo-layer (RPL) elements of lead zirconat titanate (PZT). Even if anomalous diffusion is predicted by fitting the data with M_t/M_∞=kt^α, the fractional uptake M_t/M_∞ is linear with the square root of the time up to M_t/M_∞=0.6, suggesting Fickian behavour. The anomalous values of α are probably due to experimental time lag. A dependence of the diffusion on the morphology of the material and the penetrant shape and flexibility has been found.     

Water sorption properties of poly(ethyl acrylate-co-hydroxyethyl methacrylate) macroporous hydrogels

Synthetic porous hydrogels are becoming more and more important in the field of biomaterials. Different studies demonstrate that the porous structure promotes the colonisation of living cells and improves the biocompatibility of the implants. The macroporous structure allows not only the control of cellular ingrowth morphology but also the mechanical integration and the regulation of nutrient and hydraulic flow in the hydrogel. In this work poly(ethyl acrylate-co-hydroxyethyl methacrylate) (PEA/PHEMA) copolymers were polymerized using 2% of ethylene glycol dimethacrylate as cross-linking agent and azoiso-botyronitrile as initiator. Five samples were prepared with the EA/HEMA weight ratios of 75/25, 50/50, 25/75 and pure PEA and PHEMA polymers, obtaining different degrees of hydrophilicity. The macroporous structure was obtained by adding poly(acrylonitrile) fibres to the monomers. After polymerization the fibres were eliminated by dissolution in dimethyl formamide. The holes are cylinders of approximately 40μm diameter and are all, more or less, in the same direction, although they are not uniformly distributed. Water sorption isotherms and diffusion properties of the macroporous samples are compared with the samples without holes.     

Water sorption and electrical/dielectric properties of organic-inorganic polymer blends

Organic-inorganic polymer blends (OIPB) were obtained by reaction of organic and inorganic oligomers. The organic oligomer was synthesized with 2,4-toluene diisocyanate (TDI) and oligooxypropylene glycols (OPG) with various molecular weights (MW). The inorganic component was a water solution of sodium silicate. The OIPB obtained are hydrophilic and have great water sorption ability (the relative weight of sorbed water reaches 2000 %). The kinetics of water sorption and the changes of electrical conductivity during sorption were studied. Sorption ability, and mechanical, electrical and dielectric properties of OIPB depend on molecular weight of OPG: conductivity increases with increasing MW, whereas the sorption ability correlates with the mechanical properties. The influence of the inorganic phase content on the electrical and dielectric properties was studied as well.