Journal of Radioanalytical and Nuclear Chemistry | Year: 2013
The adsorption of erbium (Er) ions on activated charcoal (AC) is investigated at temperatures 10-40 C from aqueous solutions to understand the kinetics behavior. The intra-particle diffusion, the pseudo-first order kinetic and pseudo-second order kinetic models were used to describe the kinetic data. Results shows that the adsorption of Er ions on AC occurs in two stages and the surface adsorption and diffusion phenomena are operative in the adsorption process. The result also reveals that intra-particle diffusion is not only the main rate determining step through out the adsorption process, but the boundary layer diffusion also play significant role in rate determination. Values of the intra-particle diffusion rate constant and the extent of the boundary layer diffusion were calculated. A comparison of the kinetics models on the overall adsorption rate indicates that the Er/AC system is best described by the pseudo-second order kinetic model than the pseudo-first order model, and the overall rate of the Er ions adsorption on AC appears to be controlled by more than one step, i.e., external mass transfer and diffusion mechanism. © 2012 Akadémiai Kiadó, Budapest, Hungary.
Journal of Radioanalytical and Nuclear Chemistry | Year: 2013
Large deposits of coal are abundantly available in Pakistan. An attempt has been made to check its efficacy for the cobalt ions from aqueous solutions in order to exploit the locally available naturally occurring cheaper material for the decontamination/removal of metal ions from nuclear and industrial effluents. The adsorption behavior of cobalt ions on coal powder has been studied as a function of various physicochemical parameters i.e., stirring speed, shaking time, pH, concentration of cobalt ions, temperature, etc. Conditions for the uptake of cobalt ions were established. Adsorption dynamics models such as intra-particle diffusion model, pseudo-first order kinetic model (Lagergren's equation) and pseudo-second order kinetic model were applied to the adsorption data to elucidate the adsorption process and its mechanism. Results reveal that the adsorption mechanism is predominantly diffusion and both intra-particle and boundary layer diffusion seem significant in the rate controlling step. The adsorption process is best accounted for using pseudo second order kinetic model and the overall rate of adsorption process appears to be controlled by more than one step, namely the external mass transfer and intra-particle diffusion mechanism. The existence of two slopes in the Freundlich plot also confirms the surface diffusion and intra-particle diffusion modes of adsorption. The Langmuir isotherm equation was obeyed well in the whole range of cobalt ions concentration with high value of correlation coefficient (r 2 = 0.999). The adsorption energy (E a) calculated from D-R isotherm was 6.756 kJ/mol indicating physical nature of adsorption. The adsorption of cobalt ions increased with the increase of temperature and thermodynamic parameters such as ΔH, ΔS and ΔG were calculated. Results suggested that the cobalt ions adsorption on coal powder is endothermic (ΔH 33.90 kJ/mol) and spontaneous (negative ΔG values) process. The adsorption of other metal ions on coal powder was studied at optimized condition for cobalt ions to check its selectivity. Consequently, cobalt ions can be removed from Zr, Ru Eu, Er, Sm, Gd, Dy, Ce, U, and Th ions, where as Cs, Cr and Sr ions reduces the adsorption of cobalt ions by co-adsorption and their reducing affect is in the order of Sr > Cr > Cs. © 2012 Akadémiai Kiadó, Budapest, Hungary.
Ashfaq M.,National Institute for Biotechnology and Genetic Engineering NIBGE |
Ashfaq M.,University of Guelph |
Asif M.,National Institute for Biotechnology and Genetic Engineering NIBGE |
Anjum Z.I.,Central Cotton Research Institute |
Molecular Ecology Resources | Year: 2013
Although two plastid regions have been adopted as the standard markers for plant DNA barcoding, their limited resolution has provoked the consideration of other gene regions, especially in taxonomically diverse genera. The genus Gossypium (cotton) includes eight diploid genome groups (A-G, and K) and five allotetraploid species which are difficult to discriminate morphologically. In this study, we tested the effectiveness of three widely used markers (matK, rbcL, and ITS2) in the discrimination of 20 diploid and five tetraploid species of cotton. Sequences were analysed locus-wise and in combinations to determine the most effective strategy for species identification. Sequence recovery was high, ranging from 92% to 100% with mean pairwise interspecific distance highest for ITS2 (3.68%) and lowest for rbcL (0.43%). At a 0.5% threshold, the combination of matK+ITS2 produced the greatest number of species clusters. Based on 'best match' analysis, the combination of matK+ITS2 was best, while based on 'all species barcodes' analysis, ITS2 gave the highest percentage of correct species identifications (98.93%). The combination of sequences for all three markers produced the best resolved tree. The disparity index test based on matK+rbcL+ITS2 was significant (P < 0.05) for a higher number of species pairs than the individual gene sequences. Although all three barcodes separated the species with respect to their genome type, no single combination of barcodes could differentiate all the Gossypium species, and tetraploid species were particularly difficult. © 2013 John Wiley & Sons Ltd.
Haider S.,King Saud University |
Al-Masry W.A.,King Saud University |
Bukhari N.,King Saud University |
Polymer Engineering and Science | Year: 2010
Electrospinning is an interesting technique, which provides a facile and an effective mean in producing nonwoven fibrous materials; however, for producing nanofibers, investigation of the electrospinning conditions is very important. In this study, chitosan, gelatin, and their polyelectrolyte complexes (PECs) were electrospun to prepare nonwoven nanofibrous mats. The concentrations of chitosan and gelatin solutions and electric field (kV/cm) were optimized. The solutions were then blended in different ratios (0-100%) to get electrospun nanofibrous mats. Solution concentration and electric field showed pronounced effect on the electrospinnability and fiber diameter of these systems. Mostly large beads coexisted with the fibers were observed for chitosan at 1 wt% solution concentration, which then showed good electrospinnability at 2 wt% (nanofiber diameter was 145 and 122 nm at 15 and 20 kV/10 cm, respectively), whereas gelatin showed no electrospinnability below 15 wt% solution concentration and a homogenous fibers network at 15 wt% (149 nm at 20 kV/10 cm). The morphology and diameter of chitosan-gelatin PEC nanofibers varied with the chitosan/gelatin ratio. The crystallinity of chitosan was also observed to reduce with electrospinning and addition of gelatin. © 2010 Society of Plastics Engineers.
Bumbac G.,Polytechnic University of Bucharest |
Revista de Chimie | Year: 2015
The recent energy and environmental issues urge the need to revamp the existing plants in order to minimize the energy requirements and consequently decreases environmental pollution. This paper represents an application of methods for performance analysis of existing processes and finding of retrofit solutions through the application of techniques for process modeling and simulation and process integration. An in atmospheric and in vacuum conditions crude oil distillation unit (AVCODU) from a typical refinery [Kaes G., 2002] is considered as the case study for above mentioned scope of this work. Various Heat exchanger Networks (HENs) has been developed by applying the process heat integration (HI) pinch approach. However, it has been estimated that 16.2 MW not utility and 16.22 MW of cold utility can be saved in a year by revamping of pre-heating train of AVCODU. Furthermore, capital cost of revamping can be recovered within 2.3 year of plant operation.