Effect of temperature on the removal of lead(II) by adsorption on China clay and wollastonite

The removal of Pb(II) from aqueous solution by adsorption on china clay and wollastonite is an attractive process. The amount of Pb(II) removed by adsorption is highly dependent on the temperature of the adsorbate solution and favours low temperature. The equilibrium times were noted, i.e. 90 min for china clay and 120 min for wollastonite. The various rate parameters of the adsorption process have been determined at different temperatures. The activation energies were determined and found to be ?5.345 kJ mol^?1 and ?8.730 kJ mol^?1 for Pb(II)-china clay and Pb(II)-wollastonite systems, respectively. The adsorption isotherm was measured experimentally at various temperatures. The negative values of enthalpy change (ΔH = ?77.95 kJ mol^?1 and ?16.40 kJ mol^?1 for china clay and wollastonite, respectively) indicate the exothermic nature of the adsorption processes for both systems. The isosteric heats of the adsorption process have been determined at various surface coverages of the adsorbents used. The various thermodynamic parameters have been calculated to elucidate the mechanism involved in the adsorption process.     

DC electrical conduction in solution-grown pure and iodine-doped poly(butylene terephthalate) films

DC electrical conduction in poly(butylene terephthalate) films sandwiched between planar aluminium electrodes was investigated. The films were grown by the isothermal immersion technique. The conduction process was studied in the temperature range 300–450K, with an applied electric field of 0.22 × 10⁷?6.66 × 10⁷ Vm^?1. It was found that the Richardson-Schottky type of conduction mechanism was dominant throughout the temperature range of study. The values of the Schottky field lowering constant β, the effective metalinsulator potential barrier and the activation energy were evaluated. The value of the activation energy (U = 0.7 eV) indicates the predominance of electronic conduction. The effect of impurities like iodine on electrical conduction was also investigated.     

~(252)Cf中子活化元素分析技术在工业过程控制中的应用前景

本文综述了利用~(252)Cf中子活化元素分析技术在工业过程控制中的应用现状、特点、前景和我国面临的任务。     

Electron transport in non-crystalline garnet films

Thin films of yttrium iron garnet (yig) and Gd-substitutedyig of different thickness have been prepared by flash evaporation. The surfacedc andac electrical resistivity and thermopower in these films have been studied. The results are explained on the basis of Mott and Davis model in which narrow tails of localised states exist at the extreme valence and conduction bands and a band of localised levels near the middle of the gap. For the temperature range studied, the main conduction mechanism is on account of excitation of carriers into localised states at the band edges and hopping at energies close to the band tails.     

Fusion-fission hybrids: Environmental aspects and their role in hybrid rationale

The rationale for developing hybrids depends on real or perceived liabilities of relying on pure fission to do the same job. Quite possibly the main constraint on expanded use of fission will be neither lack of fuel nor high costs, but perceived environmental liabilities—radioactive wastes, reactor safety, and links to nuclear weaponry. The environmental characteristics of hybrid systems and pure-fission systems are compared here in detail. The findings are that significant environmental advantages for hybrids cannot now be demonstrated and may not exist. Therefore, if environmental drawbacks constrain the application of pure fission, hybrids probably also will be thus constrained.     

Kinetic studies on dehydrogenation of butanol to butyraldehyde using zinc oxide as catalyst

Butyraldehyde is an important chemical for many industrial applications, especially in the production of polyvinylbutyral. A systematic study of its synthesis by catalytic dehydrogenation of butanol, using zinc oxide as catalyst has been carried out. The effect of the method of preparation of zinc oxide on its catalytic activity for the title reaction has also been studied. The optimum conditions for maximum yield have been worked out and on the basis of secondary electron micrograms the reasons for higher activity/selectivity in the case of zinc oxide calcined from zinc hydroxide is attributed to the presence of hexagonal morphology. A kinetic study for the best zinc oxide catalyst has been carried out and the rate equation has been determined.     

Effect of phase transformation on nonisothermal synthesis in mechanically activated heterogeneous systems

A mathematical model of nonisothermal synthesis in a mechanically activated system with allowance for the phase transition in one reagent is constructed. Results of studying the influence of the phase transition on the kinetics of nonisothermal chemical interaction of a pre-activated mixture for two different limiting synthesis regimes (wave and volume synthesis) are presented. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 1, pp. 56–67, January–February, 2009.     

超声细化粉煤灰性能试验研究

通过对粉煤灰进行超声细化处理 ,分析研究了超声处理的不同时间、不同超声强度对粉煤灰活性的激发影响 ,讨论比较了加入细化后的粉煤灰试块的强度变化规律     

Recycled waste paper—A new source of raw material for electric double-layer capacitors

For the first time, a new carbon–carbon composite electrode material for supercapacitors is prepared by simple KOH activation of waste newspaper. The amorphous nature and surface morphology of the carbon composite are investigated by X-ray diffraction (XRD), N₂ adsorption/desorption and scanning electron microscopy. The surface area and pore diameter are 416 m² g⁻¹ and 5.9 nm, respectively. Electrochemical characteristics are evaluated by cyclic voltammetry (CV) and charge–discharge tests in 6.0 M KOH at a 1 mA cm⁻² current density. The CV results reveal a maximum specific capacitance of 180 F g⁻¹ at a 2 mV s⁻¹ scan rate and the data explore a development of new use for waste paper into a valuable energy storage material.