Batch equilibrium tests

Generally, there is no simple and easy theoretical procedure which can provide exact or nearly precise quantitative predictions of what and how much will be adsorbed/desorbed by any solid phase over a period of time [9, 136-139]. Understanding sorption/desorption characteristics of any solid phase materials requires two main laboratory experimental techniques (a) batch equilibrium testing, and (b) continuous solid phase column-leaching testing. These involve... 

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). 

Batch equilibrium tests used for sorption isotherm determinations involve solid suspensions (i. e., the full surface area of the solid particles is exposed to... 

It is important to differentiate between the two different types of sorption/ desorption tests (i. e.,batch and column-leaching), and the sorption characteristics determined from one should not be confused with the other. Sorption isotherms obtained with batch equilibrium tests are applied mainly to solid suspensions. The physical model, assumed with this situation, is one of a completely dispersed solid particle system, where all solid particle surfaces are exposed and available for interactions with the contaminants of concern. In contrast, column-leaching tests are performed with intact solid samples, and the sorption characteristics obtained from them are the results of contaminant interactions with a structured system where not all-solid particle surfaces are exposed or available for interactions with the contaminants. 

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). 

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. 

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. 

Adsorption of surfactant on reservoir rock can be determined by static tests (batch equilibrium tests on crushed core grains) and dynamic tests (core flood) in the laboratory. The units of surfactant adsorption in the laboratory can be mass of surfactant adsorbed per unit mass of rock (mg/g rock), mass per unit pore volume (mg/mL PV), moles per unit surface area (peq/m ), and moles per unit mass of rock (peq/g rock). The units used in field applications could be volume of surfactant adsorbed per unit pore volume (mL/mL PV) or mass per unit pore volume (mg/mL PV). Some unit conversions follow ... 

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). 

The adsorption isotherm obtained through batch equilibrium tests which is generally conducted with soil suspensions cannot be considered to be representative of the sorption characteristics of intact soils. Figure 8 shows the results of sorption of Pb in a leaching column containing a kaolinite soil. For comparison, the adsorption isotherm of the same soil is also shown. The results show that there are differences not only between the adsorption characteristics of the intact soil sample and the adsorption isotherm, but also with the sorption location. The sorption characteristics between near source (source next to the leachate inlet) and away from source (source furthest away from leachate inlet) are distinctly different, and reflect the attenuation of the Pb. 

The microautoclave solvent activity tests measure coal conversion in a small batch reactor under carefully controlled conditions. The tests are described as Kinetic, Equilibrium and SRT. The Kinetic and Equilibrium Tests measure coal conversion to tetrahydrofuran solubles at conditions where conversion should be monotonically related to hydrogen transfer. The Kinetic Test is performed at 399°C for 10 minutes at an 8 to 1 solvent to coal ratio. The combination of high solvent ratio and low time provide a measure of performance at essentially constant solvent composition. The measured conversion is thus related to the rate of hydrogen donation from solvent of roughly a single composition. In contrast, the Equilibrium Test is performed at 399°C for 30 minutes at a 2 to 1 solvent to coal ratio. At these conditions, hydrogen donors can be substantially depleted. Thus performance is related to hydrogen donor... 

Spence, R. D., Delmau, L. H., Klatt, L. N., Sloop, F. V., Jr., Bonnesen, P. V., and Moyer, B. A. Batch-Equilibrium Hot-Cell Tests of Caustic-Side Solvent Extraction (CSSX) with SRS Simulant Waste and... 

Determine the Freundlich and Langmuir isotherm coefficients for the following adsorption test data on granular activated carbon (GAC). The liquid volume used in the batch adsorption tests was 1 L. The initial concentration of the adsorbate in solution was 3.37 mg/L. Equilibrium was obtained after 7 days. 

Adsorption of Strontium in Equilibrium-Type and Column Experiments. Laboratory batch equilibrium experiments were used as a rapid method for selecting ion exchangers for testing in columns. Distribution coefficients were obtained for strontium adsorption by equilibrating 1 g of resin or zeolite in 100 ml of basin water and agitating for 24 hr at ambient temperature. After centrifuging, the concenti ation of strontium-90 in the supernate was determined. Table VI shows the measured dis-... 

Single batch leaching tests (equilibrium based) Multiple batch and percolation/column testst ... 

Granular carbons take much longer periods of time to reach equilibrium. Therefore, when granular and powdered carbons are being evaluated simultaneously in batch-contact tests, granular carbons are usually pulverized and tested in powdered form. 

Batch leaching tests are designed to determine rates of desorption and equilibrium sorption relationships imder conditions of high mixing, high surface areas of the construction material, and continuous surface renewal [1-4,240-... 

The problem here was that the target molecule is very complex and unstable. The results of the rebinding test are shown after 1 and 26 h of equilibration (expressed as peak area values). The absolute absorbance decreased during this time due to template decomposition. 2-Vinyl pyridine appeared to be the most successful monomer based on the equilibrium batch rebinding tests (Fig. 15). The 2-VPY materials prepared on a larger scale and tested as chromatographic stationary phases also exhibited a certain selectivity towards the template (methotrexate, MTX) and its closely related analogues (leucovorin and folic acid) (Fig. 16). 

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 ... 

A simple experiment in which a proposed solvent is mixed with the feed mixture can be used to guide solvent selection even if the equilibrium phases are not analyzed to determine concentrations. If laboratory facilities are available, batch shakeout tests are often the most attractive way to screen solvents and quickly identify a few suitable candidates for further study. 

The adsorbent used in the experiment was zeolite synthesised from fly ash. Dyes solution with a concentration of 1000 mg/L was prepared from analytical-grade reagent and DDW. Adsorption kinetics and isotherm experiments for all samples were undertaken using a batch equilibrium technique. The adsorption of dye was performed by shaking 0.1 g of adsorbent in 100 mL of dye solution with an initial concentration of 50-1000 mg/L at 150 rpm at different temperatures. The determination of dye concentration was done on a spectrophotometer by measuring absorbance at of 464, 630 and 560 nm for methyl orange, methylene blue and safranine T, respectively. In accordance with the Lambert-Beer law, the absorbance was found to vary linearly with concentration, and dilutions were undertaken when the absorbance exceeded 0.6. The data obtained from the adsorption tests were then used to calculate the adsorption capacity, qt (mol/g), of the adsorbent by a mass-balance relationship, which represents the amount of adsorbed dye per amount of dry adsorbent. All experimental runs were conducted at 28 2°C. 

Analysis of batch adsorption tests was limited by the precision of the analytical technique. An error analysis revealed that these uncertainties could produce polymer adsorptions of 0.5 and 3.0 /tgm/gm for equilibrium solutions containing 100-, 250-, and 500-ppm polymer concentrations even when there was no adsorption. 

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