Adsorption of calcium at the zinc sulphide-water interface

1977 ◽  
Vol 30 (4) ◽  
pp. 733 ◽  
Author(s):  
MS Moignard ◽  
RO James ◽  
TW Healy
Keyword(s):  
Ion Exchange ◽  
Zeta Potential ◽  
Calcium Ions ◽  
Reasonable Agreement ◽  
Background Electrolyte ◽  
Zinc Sulphide ◽  
Pure Zinc ◽  
Subsequent Decrease ◽  
Ph Dependent ◽  
Direct Adsorption

The uptake of aqueous calcium ions by pure zinc sulphide colloids has been measured by direct adsorption and microelectrophoresis techniques. This uptake is pH dependent, with significant adsorption commencing at approximately pH 7 and increasing up to pH 11. The electrokinetic measurements also reflect the interfacial presence of Ca2+. The zeta-potential of zinc sulphide particles is more positive in the presence of Ca(NO3)2 solutions than in simple background electrolyte (KNO3) solutions. If the concentration of calcium ion is sufficiently high, the zeta-potential changes sign c. pH 8. Adsorption and simple ion-exchange models which have been successfully applied to other oxide and sulphide minerals are not particularly successful. However, reasonable agreement between direct adsorption and electrophoresis data has been obtained from the simple Gouy-Chapman-Stern double layer model, provided that: (i) the surface potential is approximately given by the Nernst equation; (ii) the specific adsorption potential of Ca2+ on ZnS increases from about 0 kBT/ion, at low pH values below pH 7, up to about - 6.5 kBT/ion, at pH 8 and higher. An ion-exchange model could only be used to give reasonable agreement with experiment at low adsorption densities. This exchange reaction is not strongly pH dependent and involves the release of one proton for every three Ca2+ ions adsorbed. These results would indicate that Ca2+ adsorption at the ZnS-H2O interface involves the movement of calcium ions into the Stern plane without the release of an equivalent number of protons into the diffuse layer and bulk solution. The subsequent decrease in zeta-potential caused by Ca2+ adsorption may be related to deteriorating flotation recoveries and grades observed for sphalerite in the presence of Ca2+ solutions when lime is used as a pH modifier and/or suppressant for pyrite.

scholarly journals ADSORBATIVE SEPARATION OF DOXYCYCLINE FROM AQUEOUS SOLUTION WITH N,N-DIETHYL N-METHYL CHITOSAN, GUM AND POLYACRYLIC ACID BASED HYDROGELS

2021 ◽  
Vol 11 (07) ◽  
pp. 44-53
Author(s):  
Mirvari Hasanova Mirvari Hasanova
Keyword(s):  
Aqueous Solution ◽  
Ion Exchange ◽  
Zeta Potential ◽  
Polyacrylic Acid ◽  
Inorganic Materials ◽  
Biologically Active ◽  
Cross Linking ◽  
Separation And Purification ◽  
Inorganic Substances ◽  
The Cross

The separation and purification of antibiotics with sorption by ion-exchange materials, as well as their delivery in biological processes by immobilization, are now widely used in biotechnology. There are many scientific studies in the literature on the sorption of antibiotics by polymer-based sorbents and inorganic materials, as well as the study of thermodynamics and kinetics of the process. In the literature, the acquisition of biologically active systems from the sorption of antibiotics by ion-exchange fibers based on various polymers and inorganic substances was carried out. However, the synthesis of selective gels for the effective separation of doxycycline and its delivery in different pH mediums by sorption with biodegradable, biocompatible polysaccharide-containing composites is one of the topical issues. Gel was synthesized from the cross-linking of N,N-diethyl N-methyl derivative of a natural polyaminosaccharide of chitosan by glutaric aldehyde. Also, pH-sensitive hydrogels that can swollen in water were synthesized from the cross-linking of a graft copolymer of cherry source gummiarabic with N-vinylpyrrolidone, as well as synthetic polymer polyacrylic acid with N,N-methylene-bis-acrylamide. The structure of the gels were identified by FTIR and NMR spectroscopy, and the sorption of doxycycline antibiotic from an aqueous solution was investigated. According to the values of zeta potential, the protonation of functional groups in the main macromolecule in an acidic medium leads to a value of zeta potential of 40÷80 mV on the surface of chitosan-based gel and others. Although the chemical structure is different, the isoelectric point is set around pH=6÷8 for all three hydrogels. The dependences of the sorption process on the amount of gels, antibiotic concentration, temperature, and pH medium were studied. The experimental data were analyzed using two adsorption models, Langmuir and Freundlich, with the later system providing the best fit. Doxycycline is adsorbed on the surface of chitosan, gummiarabic and polyacrylic acid based hydrogel composite through by physical interactions. Also, the results of thermodynamic parameters ΔG40 kJ/mol show that the nature of the adsorption process is physical, and spontaneous, too. Keywords: Chitosan, Gummiarabic-arabinogalactane, polyacrylic acid, hydrogel, sorption isoterms, doxycycline, thermodynamica.

scholarly journals On the Formation of COS from H2S and CO2 in the Presence of Zeolite/Salt Compounds

1998 ◽  
Vol 16 (7) ◽  
pp. 577-581 ◽  
Author(s):  
Wolfgang Lutz ◽  
Andreas Seidel ◽  
Bruno Boddenberg
Keyword(s):  
Carbon Dioxide ◽  
Ion Exchange ◽  
Hydrogen Sulphide ◽  
Calcium Ions ◽  
Gaseous Mixture ◽  
Degree Of Conversion ◽  
Low Level ◽  
Sodium Cations

A gaseous mixture of hydrogen sulphide and carbon dioxide (20% H2S, 80% CO2) was brought into contact at 25°C with NaY and NaX zeolites in an as-synthesized form as well as after modification by the inclusion of salts (NaCl, NaBr) in the small cages of the aluminosilicate framework and ion exchange with aqueous CaCl2 solution. At small contact times (5 h), the degree of conversion of H2S according to the reaction H2S + CO2 → COS + H2O by the various samples was found to follow the sequence NaY/NaCl ≈ NaY/NaBr ≈ NaX/NaCl(CaCl2) < NaY « NaX/NaCl ≈ NaX. Long-term runs with NaY and NaY/NaBr revealed that the latter zeolite retained a very low level of H2S conversion for contact times as long as 250 h. It is concluded that such low H2S conversion requires the absence of low-coordinated sodium cations in the supercages or their replacement by calcium ions, and blocking of the β-cages with salt anions.

Synthesis and Characterization of Pure and Mn Doped Zinc Sulphide Nanoparticles and Nanofluids

2015 ◽  
Vol 1086 ◽  
pp. 101-106
Author(s):  
M. Gopalakrishnan ◽  
Issac P. Nelson ◽  
Solomon Jeevaraj A. Kingson
Keyword(s):  
Morphological Structure ◽  
Blue Shift ◽  
Chemical Precipitation ◽  
Zinc Sulphide ◽  
Precipitation Method ◽  
Average Particle ◽  
Zns Nanoparticles ◽  
Pure Zinc ◽  
Yellow Orange ◽  
Mn Doped

In this work, pure ZnS and Mn doped ZnS nanoparticles are synthesized by simple chemical precipitation method. The structure of pure zinc sulphide and Mn doped zinc sulphide sample are analyzed by X-ray diffraction technique. The morphological structure of zinc sulphide and Mn2+doped zinc sulphide nanoparticles are studied using scanning electron microscope (SEM). The average particle sizes of pure ZnS nanoparticles are determined to be from 29 nm to 44 nm and Mn doped ZnS nanoparticles are determined to be from 99 nm to 135 nm. The optical properties of pure and Mn doped ZnS nanoparticles have been investigated by photoluminescence (PL) spectroscopy. The emission spectrum of Mn2+doped with ZnS particles of the present study shows blue shift of the yellow-orange emission peak at 590 nm. Nanofluids are prepared for six different concentrations by dispersing pure and Mn2+doped ZnS nanoparticles in de-ionized water. Thermal conductivity studies are carried out for both nanofluid systems and the results are discussed.

scholarly journals Theory of the luminosity produced in certain substances by α-rays

1910 ◽  
Vol 83 (566) ◽  
pp. 561-572 ◽  
Keyword(s):  
Preceding Paper ◽  
Zinc Sulphide ◽  
Water Molecules ◽  
Initial Value ◽  
Solid Matter ◽  
Complex Molecules ◽  
Pure Zinc ◽  
Rate Of Decay ◽  
Constant Source ◽  
Active Centres

In the preceding paper, Mr. Marsden has examined the decay of the luminosity excited by α -rays in zinc sulphide, willemite, and barium platinocyanide, when subjected to an intense bombardment by α -particles. He has shown that the luminosity decreases with continued bombardment to a very small fraction of its initial value. For a given bombardment, the rate of decay of luminosity is about the same for zinc sulphide and willemite, but is especially rapid in barium platinocyanide. The action of the α -particles on phosphorescent zinc sulphide is of special interest and importance on account of the marked scintillations observed, and the fact that each α -particle under suitable conditions produces a visible scintillation. Mr. Marsden has brought out the essential fact that the actual number of scintillations observed for a constant source of α -rays changes very little with continued bombardment, but the brightness of the scintillations rapidly diminishes. It is well known that the α -particles exert a marked dissociation effect in complex molecules on which they fall. For example, the α -rays from radium or its emanation, dissolved in water, dissociate the water molecules, producing hydrogen and oxygen at a rapid rate. I have shown elsewhere (‘Radio-active Transformations,’ p. 253), that the magnitude of this effect is in agreement with the view that each α -particle dissociates as many molecules of water as it produces ions in its path in air. The loss of energy of the α -particle in passing through a gas is mainly used up in producing ions in the gas. The laws of absorption of α -particles, which have been so carefully worked out by Bragg, show that no definite distinction as regards absorption can be drawn between a solid and a gas. It is reasonable to suppose that the α -particle produces ions in a solid as well as in a gas, and that the absorption of the α -particle is due mainly to the energy used up in this process. If the solid matter is composed of complex molecules, the latter will be dissociated by the α -particles. As Marsden has pointed out, pure zinc sulphide does not exhibit the scintillation effect, but this only appears in zinc sulphide to which certain impurities have been added. Since the amount of impurity present is of the order of 1 per cent., it is probable that only a small fraction of the total number of molecules give rise to the scintillation effect. These “active centres,” as they will be called, will on the average be uniformly distributed among the inactive molecules.

Sign in / Sign up

Export Citation Format

Share Document