Separation of lignosulfonate from its aqueous solution using supported liquid membrane

This paper presents an experimental and theoretical study on facilitated transport of lignosulfonate (LS) through a flat sheet supported liquid membrane using trioctylamine (TOA) as carrier and dichloroethane as diluent. The studies were carried out with various support materials and operating conditions (viz. carrier concentration, strip phase concentration, salt concentration, etc.) and their effects on the transport of LS. The results were analyzed to identify a suitable combination of support and operating condition that would yield best performance of the supported liquid membrane (SLM) in terms of fast and efficient transport of LS. The stability of the SLM was assessed in terms of loss of liquid from the pores of membrane support. The SLM is found to be stable till 10 h. Co-transport mechanism has been adopted in this work by using NaOH as the strip phase. It was observed that extraction of LS is increased with increase in concentration of NaOH up to a limiting value of 0.5 M NaOH. Difference of salt concentration between feed and strip phase considerably affect the separation process. The diffusional resistances of organic membrane (Δorg) and aqueous solution (Δaq) calculated from the permeation model, which is again a combination of three unique mechanisms viz., diffusion through a feed aqueous layer, a fast interfacial chemical reaction, and diffusion of carrier–complex through the organic membrane, are found to be 609.9 and 176.6 s cm⁻¹, respectively. The values of the diffusion coefficient in the membrane (D_org) and in the bulk organic phase (D_complex) are 1.67×10⁻⁹ and 6.68 × 10⁻⁸ m²s⁻¹, respectively. The extraction of LS is about 90%. Nearly 43% of LS can be recovered at optimum condition.     

Simultaneous separation of mercury and lignosulfonate from aqueous solution using supported liquid membrane

This paper presents an experimental investigation on facilitated and simultaneous transport of mercury and lignosulfonate (LS) through a flat sheet supported liquid membrane (SLM) having Nylon 6,6 as support, trioctylamine (TOA) as carrier and dichloroethane as solvent. The experiments were performed at various operating conditions such as strip phase concentration, feed pH, carrier concentration and feed concentration to find the best set of parameters that would yield the maximum separation of pure mercury as well as its mixture with LS. The experiments were performed in co-transport mode using NaOH as the strip phase. It was observed that extraction of mercury as well as its mixture increases with increase in concentration of NaOH up to a certain limit 0.1 M NaOH in case of pure solution and 0.2 M NaOH in case of mixture). Feed phase pH significantly affects the mercury separation process. However, initial feed concentration does not affect the extraction process appreciably. Separation of mixture of mercury and LS behaves in a similar way as their pure solution; however the extraction is low in comparison to pure solution. The extraction of mercury from its pure solution is about 81% in 1 h. The extraction of mercury and LS from their mixture is about 52.6% and 50.2%, respectively at optimum condition and in a period of 2 h.     

Diffuse ultrasonic backscatter at normal incidence through a curved interface

Diffuse ultrasonic backscatter techniques are useful for probing heterogeneous materials to extract microstructural parameters and detect flaws which cannot be detected by conventional ultrasonic techniques. Such experiments, usually done using a modified pulse-echo technique, utilize the spatial variance of the signals as a primary measure of microstructure. Quantitative ultrasonic scattering models include components of both transducer beams as well as microstructural scattering information. Of particular interest for interpretation of many experiments is the propagation through a liquid-solid interface. Here, a recent single-scattering model is expanded to include components needed for comparison with experiments. In particular, the Wigner distribution of the displacement profile is derived to model the beam pattern of an ultrasonic transducer through a curved liquid-solid interface. A simple Gaussian beam is used to model the transducer beam pattern. This expression is then used in conjunction with an appropriate scattering operator to complete the derivation. The theory developed is then compared with experimental results for a fine-grained steel using both a planar and a cylindrical interface. These results are anticipated to impact ultrasonic nondestructive evaluation and characterization of heterogeneous media with arbitrary curvatures.     

Positron annihilation spectroscopic studies of solvothermally synthesized ZnO nanobipyramids and nanoparticles

Zinc oxide (ZnO) samples in the form of hexagonal-based bipyramids and particles of nanometer dimensions were synthesized through solvothermal route and characterized by x-ray diffraction and transmission electron microscopy. Positron annihilation experiments were performed to study the structural defects such as vacancies and surfaces in these nanosystems. From coincidence Doppler broadening measurements, the positron trapping sites were identified as Zn vacancies or Zn-O-Zn trivacancy clusters. The positron lifetimes, their relative intensities, and the Doppler broadened lineshape parameter S all showed characteristic changes across the nanobipyramid size corresponding to the thermal diffusion length of positrons. In large nanobipyramids, vacancies within the crystallites also trapped positrons and the effects of agglomeration of such vacancies due to increased temperatures of synthesis were reflected in the variation of the annihilation parameters with their base diameters. The sizes of the nanoparticles used were all in the limit of thermal diffusion length of positrons and the annihilation characteristics were in accordance with the decreasing contribution from surfaces with increasing particle size.     

Kinetics of the oxidation of phosphinic,phenylphosphinic, and phosphorous acids by N-bromoacetamide

The oxidation of phosphinic, phenylphosphinic, and phosphorous acids by N-bromoacetamide (NBA) in acid solution, results in the formation of corresponding higher oxyacids of phosphorus. The reaction is first order with respect to NBA, second order in the oxyacid and inverse first in hydrogen ions. The oxidation of deuteriated phosphorus oxyacids showed the presence of a substantial primary kinetic isotope effect. The reaction failed to induce polymerization of acrylonitrile. Added acetamide has no effect on the reaction rate. It has been shown that the ‘inactive’ tautomer of the phosphorus oxyacids, RHP(O)OH, participates in the oxidation process. A rate-determining step involving transfer of a hydride ion from the P? H bond to the oxidant has been proposed.     

The Consensus Problem in Polities of Agents with Dissimilar Cognitive Architectures

Agents interacting with their environments, machine or otherwise, arrive at decisions based on their incomplete access to data and their particular cognitive architecture, including data sampling frequency and memory storage limitations. In particular, the same data streams, sampled and stored differently, may cause agents to arrive at different conclusions and to take different actions. This phenomenon has a drastic impact on polities—populations of agents predicated on the sharing of information. We show that, even under ideal conditions, polities consisting of epistemic agents with heterogeneous cognitive architectures might not achieve consensus concerning what conclusions to draw from datastreams. Transfer entropy applied to a toy model of a polity is analyzed to showcase this effect when the dynamics of the environment is known. As an illustration where the dynamics is not known, we examine empirical data streams relevant to climate and show the consensus problem manifest.     

Photodetachment of the Positronium Negative Ion with Exponential Cosine-Screened Coulomb Potentials

We have made an investigation to study the photodetachment of positronium negative ion (Ps ⁻) interacting with exponential cosine-screened Coulomb potentials (ECSCP) within the framework of dipole approximation. The dipole transition matrix elements are calculated using the asymptotic form of highly accurate initial wave function of the bound ionic state and plane wave for final electron–positronium state. Results for photodetachment cross section in ECSCP are reported for the screening parameter in the range [0.0,0.35] (in a₀^-1{a_0^{-1}}). Our results for the unscreened case agree nicely with some of the most accurate results available in the literature. Furthermore we make a comparative study of the photodetachment of Ps ⁻ in ECSCP with the photodetachment of Ps ⁻ in screened Coulomb potential. To the best of our knowledge, such a study on the photodetachment of Ps ⁻ in ECSCP is carried out for the first time in the literature.     

One dimensional flow of a plasma with an external magnetic field

Zusammenfassung Eine Lösung der Gleichungen der eindimensionalen Plasmaströmung in Anwesenheit eines externen magnetischen Feldes senkrecht zur Strömungsrischtung wird entwickelt im speziellen Fall: (i)P _r =3/4, (ii)c _p -constant und (iii)T=T(u).     

3-d Model for strain ordering in steel: II Relaxational effects

The spring-defect model developed by us in the accompanying paper I to discuss ferroelasticity, exhibited in the BCT phase of α-iron (BCC metals), is used to analyse anelastic relaxation across the paraelastic to ferroelastic phase transition. The kinetics of the underlying Hamiltonian representing strain-strain interactions is treated within mean-field theory. The relaxation-response relation of the linear response theory is employed to derive explicit expressions for the anelastic strain, the frequency-dependent compliance and the internal friction in terms of the basic parameters of the spring-defect model.