THERMODYNAMIC AND KINETIC STUDY OF ADSORPTION OF Ni(II) IONS ON CARBON ANODE DUST

In this study the use of carbon anode dust (CAD), which is the solid residue from aluminum production, as a low-cost adsorbent for the removal of Ni(II) ions from wastewater was investigated. A mechanism of adsorption kinetics and thermodynamics was proposed. In order to investigate the adsorption process of nickel ions on CAD three kinetic models were used: Lagergren's pseudo-first-order model, pseudo-second-order model, and the intra-particle diffusion model. Various thermodynamic parameters, such as the energy of activation (E_a), activation enthalpy (ΔH*), activation entropy (ΔS*), and free energy of activation (ΔG*), were evaluated. Observation of the value of the energy of activation suggests that the process uptake of Ni(II) ions can be described as activated chemisorption. The positive values of enthalpy of activation and free energy of activation, as well as negative values of entropy of activation, mean that the process of removal of Ni(II) ions is endothermic, non-spontaneous, and without structural changes in the solid carbon anode dust particles.     

Skeletal maturity of the hand and wrist in Oaxaca school children

Skeletal maturity of the hand and wrist (Tanner-Whitehouse II system) was assessed in a sample of 394 school children 5 to 18 years of age, in the city of Oaxaca, Mexico. The socio-economic background of the sample was relatively poor and the group appeared to have a poor nutritional history (via height and weight measurements). At most ages, the mean skeletal ages of Oaxaca school children are below the British means, and about 60 per cent of the children have skeletal ages below their chronological ages.     

Two-parameter Fisher criterion.

This paper proposes further generalization of a multiclass Fisher's criterion. A formula describing the dependence between the generalized multiclass Fisher's criterion F(Theta) and the variance criterion F(v)Theta has been obtained. Using this formula, it has been shown that the feature extraction methods based on the Karhunen-Loeve (K-L) expansions are special cases of the discriminant method. A full evaluation of heuristic methods for feature extraction based on the K-L expansion with regard to discriminant methods has been presented. A new algorithm for sequential feature extraction has been proposed and is illustrated with an example.     

Viral association with suspended solids

Laboratory models and field sewage samples were used to study viral association with particulates in suspension. Poliovirus and coliphages T2, T7 and f2 were tested for their adsorption to and elution from both organic and inorganic suspended solids at a variety of pH values and in both the presence and absence of a divalent cation. The results indicate that no one of the viruses tested can be used to describe a general pattern of adsorption. T2 and f2 readily associated with the clays used in the presence of divalent cation, while T7 and poliovirus adsorbed equally well to both organic and inorganic particulates. All viruses varied in the degree to which they associated with naturally-occurring suspended solids in primary and final sewage effluents; maximal association occurred at the pH extremes of 4.0 and 10.0 for all systems. Regardless of the conditions used to effect adsorption, all viruses tested, with the exception of f2, were infective by plaque assay in their adsorbed form. These data suggest that no one coliphage system can acceptably model the behavior of poliovirus in laboratory or field conditions. Furthermore, the results reaffirm and broaden the findings that viruses associated with suspended particulates are infective. Therefore, any system used to monitor virus levels in the environment must adequately account not only for free virus, but also for those which are solids-associated.     

Morphology of Co–Cr–Mo dental alloy surfaces polished by three different mechanical procedures

The present study aims at characterizing the three‐dimensional (3‐D) morphology of a Co–Cr–Mo dental alloy surface as a result of three different procedures used for polishing it. The sample surface morphology of the sampled surface was examined employing atomic force microscopy (AFM), statistical surface roughness parameters, and fractal analysis. An extra‐hard dental alloy of cobalt–chromium–molybdenum (Co–Cr–Mo) (Wironit^®, from BEGO, Bremen, Germany) was prepared and moulded. Different polishing treatments were carried out on three groups of six samples each—a total of 18 samples. The first group contained six electropolished (EP) samples. The second group containing six samples went through a mechanical polishing process employing green rubber discs and a high shine polishing paste applied by a rotating black brush (BB). The third group comprising six samples as well went through a mechanical polishing process by means of green rubber discs, high shine polishing paste, and a rotating deer leather brush (DL). Fractal analysis on the basis of a computational algorithm applied to the AFM data was employed for the 3‐D quantitative characterization of the morphology of the sampled surfaces. The fractal dimension D (average ± standard deviation) of 3‐D surfaces for BB samples (2.19 ± 0.07) is lower than that of the DL samples (2.24 ± 0.08), which is still lower than that of the EP samples (2.27 ± 0.09). The results indicated the BB samples as presenting the lowest values of statistical surface roughness parameters, thus the best surface finish, while the EP samples yielded the highest values. Microsc. Res. Tech. 78:831–839, 2015. © 2015 Wiley Periodicals, Inc.