Internal diffusion in a biporous adsorbent with a rectangular adsorption isotherm

1977 ◽  
Vol 26 (5) ◽  
pp. 899-904 ◽  
Author(s):  
P. P. Zolotarev ◽  
V. M. Starov ◽  
V. I. Ulin
Keyword(s):  
Adsorption Isotherm ◽  
Internal Diffusion

Modeling Trienzyme Biosensor at Internal Diffusion Limitation

2004 ◽  
Vol 9 (2) ◽  
pp. 139-144 ◽  
Author(s):  
J. Kulys
Keyword(s):  
Immobilized Enzymes ◽  
Internal Diffusion ◽  
Significant Response ◽  
Diffusion Limitation ◽  
Enzyme Reactions ◽  
Substrate Conversion ◽  
Apparent Stability ◽  
Biosensor Response

A model of biosensor containing three immobilized enzymes utilizing consecutive substrate conversion in the chain was developed. The modeling was performed at an internal diffusion limitation and a steadystate condition. The calculations showed that significant response of biosensors was produced if diffusion modules were larger than 1 for all enzyme reactions. Due to diffusion limitation the apparent stability of biosensor response increased many times in comparison to stability of the most labile enzyme of the chain.

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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