Biosorption potential of the mediterranean plant (Posidonia oceanica) for the removal of Cu2+ ions from aqueous media : Equilibrium,kinetic, thermodynamic and mechanism analysis

The biosorption characteristics of copper(II) ions using Posidonia oceanica biomass were investigated. Experimental parameters affecting the biosorption process such as pH level, contact time, biosorbent dosage and temperature were studied. The equilibrium data were applied to the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. The Langmuir model fitted very well the equilibrium data, and the maximum uptake of Cu(II) by Posidonia oceanica was found to be 76.92 mg/g. The mean free energy E (10.78 kJ/mol) from the D-R isotherm indicated a chemical ion-exchange mechanism. Kinetic results showed that the pseudo-second-order kinetic model was well fitted to the experimental data. Thermodynamic parameters depicted the exothermic nature of biosorption and the process was feasible and spontaneous. The results of FTIR (Fourier-transform infrared spectroscopy) revealed that carboxyl, amine, and hydroxyl groups on the biomass surface were involved in the biosorption of Cu(II) ions.     

Thermal Analysis of Non-linear Convective–Radiative Hyperbolic Lumped Systems with Simultaneous Variation of Temperature-Dependent Specific Heat and Surface Emissivity by MsDTM and BPES

With the advent of temperatures near absolute zero, it is often claimed that at very low temperatures the effect of thermal wave propagation must be included by the hyperbolic heat conduction equation (HHCE). In this paper the non-linear convective–radiative HHCE is investigated. Opposite to common numerical analyses, analytical expressions are obtained for the temperature variations by the multi-step differential transformation method. Some conclusions about alteration of the specific heat of the material, temperature steeping, and Vernotte number have been formulated.     

SnxSy compounds growth by controlled sulfurisation of SnO2

In this work, thin layers of semiconducting tin sulfide Sn_xS_y compounds have been prepared by sulfrisation of tin oxide SnO₂ on glass substrate. Structural studies showed that, depending on sulfur supply concentration, a mixture of SnS₂ and Sn₂S₃ is obtained at an annealing temperature of 550 °C for 2 h. From the transmission and reflectance spectra, the extinction coefficient and refractive index were calculated as guides to understanding crystal growth kinetics. On the other hand, the exploitation of these optical measurements along with optothermal investigations showed that the electronic transitions in these layers were of allowed direct type and exhibit two gaps indicating the presence of two competent sulfide phases: SnS₂ and Sn₂S₃.     

Effect of Cu/Sn Concentration Ratio on the Phase Equilibrium-Related Properties of Cu-Sn-S Sprayed Materials

Copper tin sulfide Cu-Sn-S compounds have been grown by the spray pyrolysis technique at 360 °C using SnCl₂·2H₂O, CuCl₂ and thiourea (SC(NH₂)₂ as precursors. Structural, morphological, and optical properties were studied showing that the obtained films crystallized in tetragonal and orthorhombic structures in terms of the Cu/Sn concentration ratio in the starting solution. Moreover, the deposited films showed a relatively high optical absorption coefficient of around 10⁴ cm⁻¹ and exhibited indirect transition gaps which lie within 1.17-1.38 eV domain.     

Boubaker polynomials expansion scheme (BPES) solution to Boltzmann diffusion equation in the case of strongly anisotropic neutral particles forward–backward scattering

A polynomial expansion scheme is used to solve Boltzmann neutron transport equation in the case of strongly anisotropic neutral particles forward–backward scattering.     

A method for measuring the specific heat capacity of layered structures using the Boubaker polynomials expansion scheme

An original method is used to measure the specific heat capacity of some layered structures. The conjoint theoretical–experimental measurement protocol is based on photothermal data and polynomial expansion mathematical analysis. The obtained value of the specific heat capacity for a solar cell buffer material is compared to recently reported results.     

A review on renewable energy conceptual perspectives in North Africa using a polynomial optimization scheme

In this review, general features of the renewable energy sources in the North African upper zone have been studied. The primal renewable sources of energy have been identified in Algeria, Morocco and Tunisia. Taking into account concordances and divergences of the different actors in the region, a polynomial optimization scheme has been performed in order to predict future potentials and perspectives.     

Dispersed phase morphology and fractionated crystallization of high-density polyethylene in PET/HDPE blends

The fractionated crystallization of high density polyethylene dispersed in a poly(ethylene terephthalate) matrix at composition of 15 wt-% was studied. The effect of the molecular weight of polyethylene with and without compatibilization was particularly addressed regarding its influence on the morphology of the blends. For non-compatibilized blends, the dramatic influence of the molecular weight of the polyethylene on the viscosity ratio and therefore on the dispersion is reflected on the relative intensities of the twin crystallization peaks of polyethylene that are developed upon cooling. These peaks reflect two sets of particles that are nucleated by more or less active heterogeneities. The influence of the addition of an ethylene-glycidyl methacrylate copolymer on the morphology and on the crystallization of the blends was also investigated. For a high molecular weight polyethylene, the compatibilizer shows less efficiency as far as dispersion is concerned.     

Morphology development in polyethylene/polystyrene blends: the influence of processing conditions and interfacial modification

The influence of processing conditions and interfacial modification on the morphology evolution and the composition range within which fully co‐continuous high density polyethylene/polystyrene blend structures can exist during blending in a single screw extruder was studied. Blends ranging from pure A to pure B component, with and without compatibilizer, were prepared under two different shear rates. It was found that high shear rates displaced the breakdown–coalescence balance of the dispersed nodules to the side of coalescence, narrowing the percolation domain and the critical composition for full co‐continuity decreased with increasing shear rates. The addition of a tri‐block compatibilizer induced the percolation threshold of the polystyrene phase to begin at lower percentages of polyethylene but the phase inversion point did not change. The experimental results are discussed in the light of various theoretical models. Copyright © 2005 Society of Chemical Industry