Kinetics adsorptives

The ODE-model was solved numerically during the estimation of the kinetic, adsorption, and deactivation parameters. 

The proposed mechanism of the effect of water can be supported by two other findings (i) the calculations of Maatman et al. [410] revealed that the active sites could be identified with surface silanol groups [Sect. 4.1.2.(a)] and(ii) independent studies of other authors [424—426] showed that silica gel could actually adsorb two layers of water the first layer is strongly chemisorbed whereas the second is less strongly adsorbed and retains much of the character of free water. The standard enthalpy and entropy changes on adsorption determined from kinetic adsorption coefficients, Kr and Kr, for the first and second layer, respectively [411], are consistent with this observation. 

Figure 3 shows that SC-100 has lower kinetic adsorption performance than AC-ref and SC-155, and that SC-155 has higher kinetic adsorption performance than the AC-ref in spite of its lower carbon level. As commercial activated carbons are obtained at temperatures near 1000°C, then AC-ref and SC-100 perhaps have quite the same texture of carbon microdomains, but as it is above mentioned the carbon level of the two materials is very different, then, this justifies the lower performance of SC-100. 

Cameron, D. R., and Klute, A. (1977). Convective-dispersive solute transport with a combined equilibrium and kinetic adsorption model. Water Res. 13, 183-188. 

Our main focus for this review is to briefly and critically describe some of the defluoridation techniques as a means of getting a basis to support the adsorption technique, to evaluate the defluoridation adsorbents now being utilized and those novel defluoridation adsorbents reported in literature over the last two decades, with special reference to drinking water. Emphasis is laid toward the adsorbents availability, fluoride sorption capacity and where applicable their kinetic adsorption characteristics and column performances are reported. Detailed characteristics of fluoride adsorption onto surface-tailored zeolite are provided. In addition, various adsorber configurations are reexamined and challenges to and prospects for their application to less developed countries (LDCs) are discussed. 

Note. tb is the breakthrough time at the outlet concentration cx = 10-5 mg/dm3 Wc is the kinetic adsorption capacity / e is effective overall adsorption rate coefficient m0 is the weight of bed, and ph is the bulk density of carbon bed. 

For DMMP, the effect of NaCl on the kinetic adsorption capacity is similar to TBB. However, the NaCl effect on the th for DMMP is stronger than that for TBB, especially at CNaci 5 wt.%. The DMMP breakthrough curves at 5 wt% and 15 wt% of NaCl are displaced toward shorter time (Table 1, Figure 5), in comparison with the curve for the sample without NaCl. It was not possible to measure the effect of RH because of experimental difficulties with the DMMP/water vapour mixtures. 

Langmuir-Hinshelwood kinetics adsorption v = fcac(l - ), desorption v = kd . 

Jantti suggested to use triple points of kinetic adsorption curves. He showed that this could result in a fast determination of the equilibrium value w,. To get such a quick estimate of the values of the parameters from measured values of m, he introduced equation (2) ... 

The kinetic adsorption studies in different types of adsorbers were performed with two phenolic compounds of PNP and PCP on activated carbon. A technique of isotherm stepwise linearization has been proposed and applied to approximate nonlinear isotherms for GAC adsorption. The results showed that pore and surface diffusivity are estimated satisfoctorily using this stepwise linearization technique. This study also showed that the apparent diffusivity (De), which possesses concentration dependence, could be estimated on LCB by applying the technique in high-adsorption region. 

Static Kinetic Adsorption. This study was carried out in 60 mg % solutions which had been degassed by aspiration before the protein was... 

The determination of the adsorption of gases on solids can be a time consuming matter. Already in 1969 Jantti suggested to measure three points of the initial course of the kinetic adsorption curve and to extrapolate the equilibrium value (3PM). When the specific molecular model of the adsorption of a gas on a solid surface is known and when it can be expected that only one kind of adsorption is at stake, this method delivers good results and allows a very fast stepwise measurement of adsorption isotherms-. ... 

The extended liquid-solid BET isotherm describes well the adsorption behavior corresponding to types II or III isotherms of the van der Waals classification of isotherms (see Figure 3.1). Its expression parallels that of the BET isotherm model which is often applied in gas-solid equiUbtia [3]. It assiunes the same molecular description the solute molecules can adsorb from the solution onto either the bare surface of the adsorbent or a layer of solute already adsorbed. The equation of the model is derived from kinetic adsorption-desorption relationships, assuming first order kinetics [10,85]. The expression obtained after a rather lengthy derivation is... 

Once the model atomic structure of an amorphous oxide adsorbent is created, one may proceed to simulate physical adsorption on (or in) this material. The peculiarity of oxide adsorbents (compared to carbon adsorbents for example) is that one has to take account of the highly inhomogeneous electrostatic field at their surfaces. The problem of the reliable calculation of the effect this field upon the adsorption energy is not yet totally resolved. However, an effective adsorption potential is typically used in such situations, with parameters that are adjusted by, for example, fitting the calculations to the temperature dependence of the experimental Henry s Law constants. Such potentials generally give reasonable values for other simulated equilibrium and kinetic adsorption properties. There is even an indication that the effective parameters of the gas-solid adsorption potential are sometimes transferrable from one (oxide) adsorption system to another. 

Semiconductor photoeffects in a complex redox electrolyte are greatly affected by such solution properties as solution redox level and stability, interfacial kinetics (adsorption), conductivity, viscosity, ionic activity, and transparency within a crucial wavelength region. Suitable redox electrolytes are known to inhibit unfavourable phenomena such as surface recombination and trapping (McEvoy et al, 1985). In... 

Hachiya, K., Takeda, K., and Yasunaga, T, Pressure-jump method to adsorption-desorption kinetics. Adsorption Sci. Technol.. 4. 25, 1987. 

For designing and developing catalysts, the focal point of all research, the pay-off, is correlation between catalyst properties on the one hand and mechanisms on the other. Choice of the active components, type of support and promotion, method of preparation, pretreatment, and formulation must be related to mechanism, kinetics, adsorption, or mass transfer. Often data are incomplete or speculative. Correlations may be empirical but prove... 

Kinetic coefficients. The kinetic adsorption and desorption coefficients can be estimated [82, 219, 412] if the form of the potential (Z) of interaction between a particle (a surfactant molecule) and the solution surface is known here Z is the coordinate measured from the surface into the bulk of liquid. If the function (Z) has the form of a potential barrier with a potential well, then the saddle-point method [261] implies... 

Many adsorption experiments on long chain fatty acids and other amphiphiles at the liquid/air interface and the close agreement with the von Szyszkowski equation is logically one proof of the validity of Langmuir s adsorption isotherm for the interpretation of y - log c -plots of typical surfactants in aqueous solutions (cf. Appendix 5D). This evidence is also justification for use of the kinetic adsorption/desorption mechanism based on the Langmuir model for interpreting the kinetics and dynamics of surface active molecules. 

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