HCl Concentration (hcl + concentration)

Distribution by Scientific Domains


Selected Abstracts


Palladium and platinum sorption on a thiocarbamoyl-derivative of chitosan

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
A. Butewicz
Abstract Immobilizing thiourea onto chitosan allowed using the polymer for the recovery of platinum groups metals (PGMs) in acidic solutions (up to 1,2M HCl concentrations). At low HCl concentration protonated amine groups may sorb chloroanionic metal species (electrostatic attraction mechanism); however, most of sorption proceeds through chelation on sulfur containing groups (less sensitive to acidic conditions). The bi-site Langmuir equation was used for fitting sorption isotherms. The sorption of PGMs was weakly affected by the composition of the solution (presence of high concentration of anions and base metals). Maximum sorption capacities for Pd(II) and Pt(IV) ranged between 274 and 330 mg g,1 in 0.25M HCl solutions and decreased to 150,198 mg g,1 in 2M HCl solutions: Pd(II) sorption was systematically higher than Pt(IV) sorption. The pseudo-second rate equation was used for modeling the uptake kinetics. Agitation speed hardly affected uptake kinetics indicating that external diffusion resistance is not the rate controlling step. Desorption yield higher than 85% were obtained using thiourea in 0.1M HCl solution. The adsorbents could be reused for at least three cycles. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]


Control of Phase and Pore Structure of Titania Powders Using HCl and NH4OH Catalysts

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2001
Ki Chang Song
Porous titania powders were prepared by hydrolysis of titanium tetraisopropoxide (TTIP) and were characterized at various calcination temperatures by nitrogen adsorption, X-ray diffraction, and microscopy. The effect of HCl or NH4OH catalysts added during hydrolysis on the crystallinity and porosity of the titania powders was investigated. The HCl enhanced the phase transformations of the titania powders from amorphous to anatase as well as anatase to rutile, while NH4OH retarded both phase transformations. Titania powders calcined at 500C showed bimodal pore size distributions: one was intra-aggregated pores with average pore diameters of 3,6 nm and the other was interaggregated pores with average pore diameters of 35,50 nm. The average intra-aggregated pore diameter was decreased with increasing HCl concentration, while it was increased with increasing NH4OH concentration. [source]


Site-selective anodic etching of InP substrate using self-organized spheres as mask

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2010
Takayuki Yokoyama
Abstract Ordered microstructures were formed on an InP substrate by metal-assisted chemical etching or anodic etching using a layer of colloidal crystals consisting of polystyrene spheres as a mask. When the metal-assisted chemical etching of the InP substrate was carried out in a mixed solution of H2SO4/H2O2 using a Pt honeycomb pattern as a catalyst, obtained by ion sputtering through the mask on the substrate, InP column arrays with a close-packed configuration having an ordered periodicity were formed. Furthermore, by anodic etching at the optimum HCl concentration with a layer of colloidal crystals as a mask, InP disk arrays or pillar arrays were fabricated. [source]


Predicting HCl concentrations in fire enclosures using an HCl decay model coupled to a CFD-based fire field model

FIRE AND MATERIALS, Issue 7 2007
Z. Wang
Abstract The amount of atmospheric hydrogen chloride (HCl) within fire enclosures produced from the combustion of chloride-based materials tends to decay as the fire effluent is transported through the enclosure due to mixing with fresh air and absorption by solids. This paper describes an HCl decay model, typically used in zone models, which has been modified and applied to a computational fluid dynamics (CFD)-based fire field model. While the modified model still makes use of some empirical formulations to represent the deposition mechanisms, these have been reduced from the original three to two through the use of the CFD framework. Furthermore, the effect of HCl flow to the wall surfaces on the time to reach equilibrium between HCl in the boundary layer and on wall surfaces is addressed by the modified model. Simulation results using the modified HCl decay model are compared with data from three experiments. The model is found to be able to reproduce the experimental trends and the predicted HCl levels are in good agreement with measured values. Copyright 2006 John Wiley & Sons, Ltd. [source]


Palladium and platinum sorption on a thiocarbamoyl-derivative of chitosan

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
A. Butewicz
Abstract Immobilizing thiourea onto chitosan allowed using the polymer for the recovery of platinum groups metals (PGMs) in acidic solutions (up to 1,2M HCl concentrations). At low HCl concentration protonated amine groups may sorb chloroanionic metal species (electrostatic attraction mechanism); however, most of sorption proceeds through chelation on sulfur containing groups (less sensitive to acidic conditions). The bi-site Langmuir equation was used for fitting sorption isotherms. The sorption of PGMs was weakly affected by the composition of the solution (presence of high concentration of anions and base metals). Maximum sorption capacities for Pd(II) and Pt(IV) ranged between 274 and 330 mg g,1 in 0.25M HCl solutions and decreased to 150,198 mg g,1 in 2M HCl solutions: Pd(II) sorption was systematically higher than Pt(IV) sorption. The pseudo-second rate equation was used for modeling the uptake kinetics. Agitation speed hardly affected uptake kinetics indicating that external diffusion resistance is not the rate controlling step. Desorption yield higher than 85% were obtained using thiourea in 0.1M HCl solution. The adsorbents could be reused for at least three cycles. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]