The correct interpretation of tetramethylthiourea electrosorption data in 3 M NaClO4 solution

2011 ◽  
Vol 76 (12) ◽  
pp. 1879-1893
Author(s):  
Jolanta Nieszporek
Keyword(s):  
Adsorption Isotherm ◽  
Mercury Electrode ◽  
Correct Interpretation ◽  
Naclo4 Solution

Tetramethylthiourea (TMTU) electrosorption behaviour at the mercury electrode in 3 M NaClO4 has been examined. Using a new concept of adsorption isotherm, new theoretical expressions have been proposed. The application of these equations shows evident influence of the electrode charge on the TMTU adsorption. It can be concluded that TMTU molecules are largely specifically bonded and at zero electrode charge the change of adsorbed TMTU molecules orientation is observed.

Cellulose Acetate Reverse Osmosis Membrane Structure

1972 ◽  
Vol 30 ◽  
pp. 528-529
Author(s):  
H. K. Plummer ◽  
E. Eichen ◽  
C. D. Melvin
Keyword(s):  
Cellulose Acetate ◽  
Reverse Osmosis ◽  
Membrane Structure ◽  
Freeze Drying ◽  
Dense Layer ◽  
Water Removal ◽  
Reverse Osmosis Membrane ◽  
Correct Interpretation ◽  
Electron Image ◽  
Scanning Electron

Much of the work reported in the literature on cellulose acetate reverse osmosis membranes has raised new and important questions with regard to the dense or “active” layer of these membranes. Several thickness values and structures have been attributed to the dense layer. To ensure the correct interpretation of the cellulose acetate structure thirteen different preparative techniques have been used in this investigation. These thirteen methods included various combinations of water substitution, freeze drying, freeze sectioning, fracturing, embedding, and microtomy techniques with both transmission and scanning electron microscope observations.It was observed that several factors can cause a distortion of the structure during sample preparation. The most obvious problem of water removal can cause swelling, shrinking, and folds. Improper removal of embedding materials, when used, can cause a loss of electron image contrast and, or structure which could hinder interpretation.

Computers and diffraction analysis

1989 ◽  
Vol 47 ◽  
pp. 44-45
Author(s):  
J. A. Eades
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Diffraction Analysis ◽  
Electron Diffraction Analysis ◽  
Image Simulation ◽  
Correct Interpretation ◽  
High Profile ◽  
High Resolution Images ◽  
Image Simulations

For well over two decades computers have played an important role in electron microscopy; they now pervade the whole field - as indeed they do in so many other aspects of our lives. The initial use of computers was mainly for large (as it seemed then) off-line calculations for image simulations; for example, of dislocation images.Image simulation has continued to be one of the most notable uses of computers particularly since it is essential to the correct interpretation of high resolution images. In microanalysis, too, the computer has had a rather high profile. In this case because it has been a necessary part of the equipment delivered by manufacturers. By contrast the use of computers for electron diffraction analysis has been slow to prominence. This is not to say that there has been no activity, quite the contrary; however it has not had such a great impact on the field.

Competitive adsorption of organic solvents using modified and unmodified calcium bentonite clay mineral

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Adsorption Isotherm ◽  
Adsorption Capacity ◽  
Organic Solvents ◽  
Competitive Adsorption ◽  
Correlation Factor ◽  
Isotherm Model ◽  
Isotherm Models ◽  
High Concentration ◽  
Dual Purpose ◽  
Calcium Bentonite

Dodecyltrimethylammonium bromide (DTAB)–modified and unmodified calcium bentonite were both used for the competitive adsorption of aromatics (xylene, ethylbenzene and toluene) and petroleum products (gasoline, dual purpose kerosene and diesel) from their aqueous solution. Infrared spectroscopy (IR) and expansion tests (adsorption capacity and Foster swelling) measurement were performed in order to evaluate the performance of the adsorbents. The Foster swelling index and adsorption capacity of the DTAB modified calcium bentonite in the organic solvents follow the trend: xylene > ethylbenzene > toluene > gasoline > dual purpose kerosene (DPK) > diesel > water. However, the adsorption capacity of the adsorbent in diesel outweighed the adsorption capacity in DPK at high concentration of DTAB indicating that diesel has higher affinity for high DTAB concentration than DPK. The percentage removal of the solvent is directly proportional to the concentration of DTAB used in modifying the bentonite as well as the contact time between the adsorbent and the solvent, hence modified calcium bentonite adsorbed a higher percentage of organic solvents than the unmodified calcium bentonite. The adsorption characteristics of both adsorbents improved remarkably after proper agitation of the organic solvents, the unmodified calcium bentonite however adsorbed more water than the modified bentonite. Data obtained from adsorption isotherm models confirms that Freundlich adsorption isotherm model was favored more than Langmuir adsorption isotherm model with the correlation factor (R2) of the former tending more towards unity. The adsorption of ethylbenzene using DTAB modified and unmodified calcium bentonites follow a pseudo second order kinetics mechanism, suggesting that the rate determining step of adsorption involves both the adsorbent and the organic solvent.

Gasoline Desulphurization by Reactive Adsorption on ZnO /Bentonite

2019 ◽  
Vol 70 (1) ◽  
pp. 50-53
Author(s):  
Constantin Sorin Ion ◽  
Mihaela Bombos ◽  
Gabriel Vasilievici ◽  
Vasile Matei
Keyword(s):  
Zinc Oxide ◽  
Adsorption Isotherm ◽  
Operating Temperature ◽  
Continuous System ◽  
Particle Sizes ◽  
Textural Characteristics ◽  
Reactive Adsorption ◽  
Atmospheric Distillation ◽  
Increased Pressure

Desulfurization of atmospheric distillation (DA) gasoline was performed by reactive adsorption on ZnO/ bentonite. The adsorbent was characterized by determining the distribution of particle sizes of zinc oxide powdered, adsorption isotherm and textural characteristics of granulated adsorbent. Adsorption experiments of atmospheric distillation gasoline were performed in continuous system at 280-320oC, 5-25 bar and volume hourly space velocities of 1-1.5 h-1. The adsorption on ZnO/ bentonite has been favored by increased pressure and operating temperature.

Desorption of Cationic Polyacrylamide from Bleached Kraft Pulp Fibers

1987 ◽  
Vol 19 (5-6) ◽  
pp. 939-951 ◽  
Author(s):  
Clifton F. Warren ◽  
R. Gehr
Keyword(s):  
Adsorption Isotherm ◽  
Total Nitrogen ◽  
Kraft Pulp ◽  
Detection System ◽  
Cationic Polyelectrolyte ◽  
Chemiluminescence Detection ◽  
Pulp Fibers ◽  
Paper Manufacturing ◽  
Bleached Kraft Pulp ◽  
Receiving Water

The adsorption and desorption behaviour of a cationic polyelectrolyte contacted with wood pulp fibers was determined by total nitrogen analysis using a pyrolysis/chemiluminescence detection system. Dialysed polymer generated an adsorption isotherm of higher affinity than did non-dialysed polymer. Capacity adsorption was maximized at pH 7, but decreased in the presence of alum depending on the dosage. Desorption of non-dialysed polymer was caused by changes in pH above or below 7.0 as well as by addition of alum. However for the alum doses typically encountered in paper manufacturing, significant desorption is unlikely. Nevertheless, the contaminants in non-dialysed polymers do hinder adsorption, and effluents from those processes using both alum and polymer may contain quantities of unadsorbed or desorbed polyelectrolytes which could be damaging to receiving water bodies.

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