Continuous adsorption

Figure 15. Comparison of curves Jm (a) and /u (b) versus t predicted by different submodels for a system with linear adsorption. Continuous line rigorous solution of transientwithboundaryconditioncM(/o + 0 = V7 dashedline rigorous(transient)...

According to Groot (2000), the mechanism of interaction between a polymer and surfactant may be deduced by considering parameters such as polymer size, mode of surfactant adsorption (continuous or discrete micelles), and possible sites of interaction (head group or tail). For the case of the mechanism of the interaction between chitosan and sorbitan esters, the polymer concentration (dilute, semi-dilute, concentrated) of... 

II Figure 1). Adsorption continually occurs around the bubbles to replace protein in areas of the interface where coagulation or stretching of the film is occurring. The actual bubble size in the foam depends upon the rate of protein adsorption as well as upon the ease of film rupture. The protein films on adjacent bubbles come in contact and trap the liquid, preventing it from flowing freely. This restriction is governed by the viscosity of the colloidal solution. The polypeptides of denatured proteins situate to positions where their hydrophobic side chains are directed outward toward each other. Because liquid... 

N diffuses into the structural pores of clinoptilolite 10 to 10 times faster than does CH4. Thus internal surfaces are kinetically selective for adsorption. Some clino samples are more effective at N2/CH4 separation than others and this property was correlated with the zeolite surface cation population. An incompletely exchanged clino containing doubly charged cations appears to be the most selective for N2. Using a computer-controlled pressure swing adsorption apparatus, several process variables were studied in multiple cycle experiments. These included feed composition and rates, and adsorber temperature, pressure and regeneration conditions. N2 diffusive flux reverses after about 60 seconds, but CH4 adsorption continues. This causes a decay in the observed N2/CH4 separation. Therefore, optimum process conditions include rapid adsorber pressurization and short adsorption/desorp-tion/regeneration cycles. 

Figure 5 illustrates the mixed gas diffusion data for a pair of runs using 60% CH4/4OX N2 as the feed gas. Note that N adsorption is a maximum at about 10 seconds for ZBS-15 while CH4 adsorption continues even after 15 minutes. It is important to realize that since N2 diffusion reverses after 10 seconds, Q in... 

Ishihara, A., Wang, D.H., Dumeignil, F., Amano, H., Qian, E.W.H., and Kabe, T. Oxidative desulfurization and denitrogenation of a light gas oil using an oxidation/adsorption continuous flow process. Applied Catalysis. A, General, 2005, 279, 279. 

Curve 2 indicates that above a certain relative pressure, negative deviation from the straight line occurs. The straight line portion of the curve is an indication of unhindered multilayer adsorption. As the adsorption continues. 

It chemisorbs oxygen from the air at room temperature, the adsorption continuing for extended periods of time. 

Behenic Ac id-n-Hexadecane Series. The general pattern of the adsorbed acid in this series (Figure 5) can perhaps best be described as a monolayer with well-defined holes, which become smaller as adsorption continues. This structure is clearly shown in BH-3, where the holes at that stage of adsorption range from approximately 200 to 1000 A. in diameter. This mode of adsorption is opposite to that observed for all the preceding acid-solvent pairs, where the polar molecules adsorbed initially in patches which increased in size and perhaps number to form the complete monolayer. The small projections in BH-2 are thought to be from the substrate and not part of the acid structure, because similar projections were occasionally observed on untreated microscope slides. 

In most techniques for studying adsorption on metals, xmiform, clean, and reproducible metal surfaces are difficult to prepare and the adsorption process cannot be followed continuously [2, 3,4,7,10,11,16, 18,2l]. Clean and reproducible metal surfaces are also difficult to prepare and maintain in methods that measure adsorption continuously and directly on a metal-coated window of a Geiger tube [l, 6,7,13]. A recently developed apparatus and technique provide controlled conditions for the production and maintenance of relatively clean metal films and the precise measurement of adsorption [20j. Metal is evaporated onto a mica window supported within a high-vacuum apparatus adsorption onto the metal film is measured directly and continuously by a counter tube below the window. 

The theoretical model described by Eqs. (2.124)-(2.128) predicts for n> 20-25 mN/m a subsequent unrealistically sharp increase of surface pressure with a weak increase of protein concentration, and simultaneously a slight increase in adsorption. This contradicts with experimental data which show, starting from some protein concentration, that n remains almost constant, while the adsorption continues to increase. This results in an increased... 

In Fig. 9a), isotherms for nitrogen gas adsorption at 77 K are compared for three ACFs [23,24] the coiTespondii PSDs are shown on F. 10. For activated carbon liber AS, the adsorption of nitrogen gas reached almost saturation at P/Po below 0.05. For A20, however, a gradual increase in adsorption continues up to P/Pg of 0.3, after an abrupt initial increase in adsorption. These abrupt initial adsorptions are due to filling of micropores with size <1 nm. 

After long and successful use in the drinking water treatment industry, activated carbon adsorption continues to gain popidarity in the wastewater treatment field to remove organics that are resistant to conventional biological treatment processes. To date, most appUcations are for more than secondary treatment and use granular activated carbon raftier than the powdered version. 

Adsorption Kinetics. Figures 2A and 2B show the FN adsorption kinetics on the three surfaces from 0,07 and 0,21 mg/ml FN solutions respectively. Each line is the average of two experiments on a given polymer. At each protein concentration, the initial rate of adsorption is independent of the type of polymer substrate, and adsorption from 0,21 mg/ml is nearly 3 times faster than from 0,07 mg/ml FN, The initial adsorption rates are linear in time until adsorption exceeds 0.06 ug/cm on PEO-PEUU and 0.10 ug/cm on the other polymers (data not shown). This suggests that the adsorption is diffusion controlled up to the above surface concentrations, after which point the adsorption rate decreases and becomes dependent upon the polymer surface chemistry. The amount of FN adsorbed does not reach a plateau within 120 minutes, nor does it reach a plateau when adsorption continues for 18 hours (data not shown). 

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