Batch equilibrium studies

The sorption behavior of 11 PAH compounds (a training set, Table 11) on various solid phases (e.g., three soils and two sediments) with different properties to relevant sorption (e.g., organic carbon content, clay content, pH, cation exchange capacity CEC Table 12), was determined by batch equilibrium studies [1]. Batch equilibrium tests were designed to determine rates of equilibrium sorption under conditions of high mixing and high surface areas of the solid particles (see Chap. 3). 

Adsorption coefficients may be determined experimentally by batch equilibrium studies (e.g. OECD, 1983). Dispersions with a defined soil/solution ratio, containing each of several initial concentrations of the chemical, are agitated until equilibrium is achieved. The phases are separated by centrifugation and the compound s concentration is determined in the aqueous fraction. The reduction in concentration of the dissolved chemical in water is used as a measure of sorption. A desorption test is conducted consecutively and the adsorption isotherms are determined. Variability in the measured soil sorption coefficients may arise from ... 

Whereas batch equilibrium tests are designed to study equilibrium sorption of solid phase particles with various pollutants, singly or in combination with other pollutants, solid phase column-leaching tests study both sorption and diffusion of organic pollutants through the subsurface environment [10,11,127, 141,142]. 

Batch equilibrium tests are conducted on solid phase suspensions, prepared with previously air-dried solids, ground to uniform powdery texture for mixing with various concentrations of the pollutants of interest in solution. The concentrations of these pollutants or the COMs leachate in the solution are designed to evaluate the capability of the suspended solids to adsorb all the pollutants possible with increasing amounts of available pollutants, consistent with interaction characteristics dictated by the surface properties of the solids and the pollutants [1,16,22-26,66,67,71]. For a successful and proper study of solid particle sorption of pollutants, the requirement for complete dispersion of solid particles in solution is absolute [143 -145]. Common practice is to use a solution to solid ratio of 10 1 [1], together with efficient sample agitation at a constant temperature (e.g.,48 h at 20 °C). 

Isotherms are normally developed to evaluate the capacity of the carbon for the adsorption of different contaminants. Data are obtained in batch tests, which determine the equilibrium relationship between the compound adsorbed on the carbon and that remaining in solution. The isotherms are used as screening tools to determine which carbon is suitable for a given application. Batch equilibrium tests are often complemented by dynamic column studies to determine system size requirements, contact time, and carbon usage rates [19]. Other parameters that are used to characterize activated carbons for water treatment include phenol number, an index of the ability to remove taste and odor, and molas.ses number, which correlates with the ability to adsorb higher molecular weight substances. However, these parameters still do not reflect performance in service, and they can only be considered as guidelines. 

Batch contact studies have shown that both Am(III) and Pu(IV) transfer rapidly at 23 to 25°C between DHDECMP-diluent solutions and aqueous HNO3. In all tests conducted, equilibrium was reached in <30 seconds. 

Whilst practical outdoor uses of PBO are unlikely to lead to significant amounts of the chemical reaching soil, its potential tor leaching has been assessed in a soil batch adsorption equilibrium study and soil column leaching studies using nonaged and aged PBO residues. 

Fig. 13 shows the results of a batch kinetic study (fractional metal uptake vs. time) comparing the parent chelating exchanger with the CIM under otherwise identical conditions. Fractional metal uptake, F t), is dimensionless and is defined as the ratio of the metal uptake q t) after time t and the metal uptake at equilibrium, i.e., F t) = q t)/(P. Although the parent chelating microbeads were bigger in average diameter (50-100 mesh) than the microbeads within the CIM, the copper uptake rate, as speculated, was... 

Korbach, P.F. Stewart, W.E. Kinetic and equilibrium studies of benzene hydrogenation in batch... 

The study of a particular adsorption process requires the knowledge of equilibrium data and adsorption kinetics [4]. Equilibrium data are obtained firom adsorption isotherms and are used to evaluate the capacity of activated carbons to adsorb a particular molecule. They constitute the first experimental information that is generally used as a tool to discriminate among different activated carbons and thereby choose the most appropriate one for a particular application. Statistically, adsorption from dilute solutions is simple because the solvent can be interpreted as primitive, that is to say as a structureless continuum [3]. Therefore, all equations derived firom monolayer gas adsorption remain vafid. Some of these equations, such as the Langmuir and Dubinin—Astakhov, are widely used to determine the adsorption capacity of activated carbons. Batch equilibrium tests are often complemented by kinetics studies, to determine the external mass transfer resistance and the effective diffusion coefficient, and by dynamic column studies. These column studies are used to determine system size requirements, contact time, and carbon usage rates. These parameters can be obtained from the breakthrough curves. In this chapter, I shall deal mainly with equilibrium data in the adsorption of organic solutes. 

Although batch laboratory studies give usefid information on the application of adsorption to tlie removal of specific waste constituents, continuous carbon filters provide the most practical application of tliis process in waste treatment. Indeed, the continuous process enables the use of high capacities in equilibrium with influent concentration rather than effluent concentration and allows biological activity, which may affect adsorption, to be taken into account. 

New silica gel phases were synthesized by a single-step reaction via immobilization of 5-formyl-3-arylazosalicylic acid derivatives on the surface of silica gel. These phases proved to show an excellent improvement in the Fe(III) extraction the determined mmol/g is in the range 1.24—1.32. The process of selective extraction of Fe(III) in the presence of an interfering ion was studied by both column and batch equilibrium techniques. Cr(in) was found to cause interference based on the affinity for binding to the chelation centers of the salicylic acid moiety of the silica gel phase. Mg, Ca, and Mn ions exhibited minimum interference in Fe(III) extraction. A group of six divalent metal ions (Co, Ni, Cu, Zn, Cd, and Pb) were found to show a specific interference based on the availability and participation of arylazo-moiety. The structures of these silica gel phases-immobilized-5-formyl-3-arylazosalicylic acids are shown in Scheme 9. 

A batch equilibrium method, as a function of pH and shaking time, was performed to characterize the metal uptake properties of silica gel-immobiUzed-aminophenol and aminobenzoic acid. Studies were made and evaluated on the basis of column application of immobilized chelating sorbents for the removal of various metal ions from sugar cane molasses. These revealed that they have higher preference toward Mn(II), Fe(III), Co(II), Cu(II), and Zn(n) rather than alkali and alkaline earth metals.The structures of the modified silica gel phases are shown in Scheme 10. 

Selective solid-phase extractors and preconcentrators of Hg(II) were synthesized and studied. These modified silica gel phases are based on chemical immobilization and physical adsorption of dithizone as well as chemical immobilization of dithiocarbamate on some amine-modified silica gel phases. The mmoFg values as the metal capacities of these modified silica gel phases were determined for a series of metal ions under the effect of pH of metal ions and the equilibration shaking times by the batch equilibrium technique. The modified silica gel phases were found to exhibit excellent affinity toward selective extraction of Hg(ll) in presence of other interfering metal ions. The potential applications of these modified silica gel phases as selective solid-phase extractors and preconcentrators for Hg(II) from natural water samples were also studied and the results indicated excellent extraction of Hg(II) with insignificant contributions by matrix effects. " " ... 

Silica gel-chemically immobilized-Eriochrome black T was synthesized and the surface coverage was found to be 0.38 mmol/g. The stability toward hydrolysis of this silica gel phase in various buffer solutions (pH 1.0-10.0) was studied and evaluated. The applicability of silica gel phase-immobilized-Eriochrome black T as a solid-phase extractor for Zn(II), Mg(II), and Ca(ll) was performed by the batch equilibrium technique and was found to show an order similar to the formation constant values of the three metal ions with the indicator. The separation and selectivity of this modified silica gel for these metal ions, based on a column technique, were found to afford a reasonable performance of the three studied metal ions. The structure of silica gel-chemically immobilized-Eriochrome black T is given in Scheme 20. 

Batch equilibrium tests are often complemented by dynamic column studies to determine system size requirements, contact time and carbon usage rates. These parameters can be obtained from the breakthrough curves (Section 4.5.2). 

Hence as the interfacial area or the length of contact time between the bubble and the oil is increased, the vaporization efficiency increases and the vapor-phase partial pressure of the volatile component approaches the value in equilibrium with the liquid phase. Batch deodorizer studies [3] have suggested that practical values for the vaporization efficiency are in the range of 0.7-0.9, which is consistent with values for steam distillation in other industries. 

Because hydrolytic reactions are reversible, they are seldom carried out in batch wise processes [26,28,36,70]. The reactor is usually a double jacket cylindrical flask fitted with a reflux condenser, magnetic stirrer, and thermometer connected with an ultrathermostat. The catalyst is added to the reaction mixture when the desired temperature has been reached [71,72]. A nitrogen atmosphere is used when the reactants are sensitive to atmospheric oxygen [36]. Dynamic methods require more complicated, but they have been widely used in preparative work as well as in kinetic studies of hydrolysis [72-74]. The reaction usually consists of a column packed with a layer of the resin and carrying a continuous flow of the reaction mixture. The equilibrium can... 

In this paper we formulated and solved the time optimal problem for a batch reactor in its final stage for isothermal and nonisothermal policies. The effect of initiator concentration, initiator half-life and activation energy on optimum temperature and optimum time was studied. It was shown that the optimum isothermal policy was influenced by two factors the equilibrium monomer concentration, and the dead end polymerization caused by the depletion of the initiator. When values determine optimum temperature, a faster initiator or higher initiator concentration should be used to reduce reaction time. 

In this work, the waste brewery yeast and Aspergillus niger were used for the adsorption of lead, copper and cadmium, and their cyanide complexes. Biosorption equilibrium was studied in a batch reactor with respect to pH, initial concentration of heavy metal and metal-cyanide complex. Biosorption equilibrium over the temperature range of 288K - 308K was investigated and the biosorption heat was evaluated. 

Alteration is always a cause for concern in geochemical investigations and the best approach will always be to avoid samples with visual or chemical evidence for alteration. The differential fluid mobility of U, Th, Pa and Ra undoubtedly provides the potential for weathering or hydrothermal circulation to disturb the U-series signatures of arc lavas. In a study of lavas from Mt. Pelee on Martinique, Villemant et al. (1996) found that domeforming lavas were in U-Th equilibrium whereas plinian deposits from the same eruptions had small U-excesses which they interpreted to reflect hydrothermal alteration. However, whilst the addition of U could be due to hydrothermal alteration, the plinian deposits were also displaced to lower °Th/ Th ratios which cannot. Instead, the two rock types may just be from separate magma batches. 

The assessment of reaction kinetics by means of batch tests may be strongly affected by dye adsorption on the biophase and supports. The relevance of the adsorption phenomena of dyes on biophase has been addressed in studies regarding free cells [41], granular support biofilm [24], entrapped cells [11, 18], anaerobic sludge [10,24,31,34] and biological activated carbon (BAC) [42,45,47,48]. They have pointed out that the kinetics may be overestimated if the assessment of the adsorption contribution to the dye removal is not taken into account. Under batch conditions, the dye is fastly split between the liquid phase and the biophase, resulting in a sharp reduction of the dye concentration in the liquid phase until adsorption equilibrium is approached. The rate of dye adsorption must be estimated and ruled out in the kinetic assessment. 

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