Sorption studies

Schwarzenbach, R. P., Westall, J. (1981) Transport of nonpolar compounds from surface water to groundwater. Laboratory sorption studies. Environ. Sci. Technol. 11, 1360-1367. 

M. J. Kontny, in Water Vapor Sorption Studies on Solid Surfaces, Ph.D. Thesis, University of Wisconsin—Madison, 1985. 

Recent sorption studies tend to support this interpretation. Based on sorption studies on USY-zeolites, Lohse et al. (36) concluded that whole sodalite units are destroyed during the dealumination and rebuilding of the framework in USY-zeolites. Such sodalite units provide the silica necessary to fill the large number of framework vacancies left by dealumination. The consumption of whole sodalite cages leads to the formation of "secondary" pores (vide infra). 

Acid properties. The acid properties of zeolites, including those of aluminum-deficient zeolites, have been described in several reviews (e.g. 33-35). The methods used to study the acidity of aluminum-deficient Y zeolites include infrared spectroscopy (primarily pyridine and ammonia sorption studies), n-butylamine titrations in the presence of Hammett or arylmethanol indicators, and to a lesser extent potentiometric titrations and calorimetric measurements. 

Pyridine sorption studies have shown the presence of both Bronsted and Lewis acid sites in USY zeolites, although to a lesser extent than in the corresponding HY zeolite (51,53). Acidity is maintained even after strong dehydroxylation of USY-B at 820°C. Rehydration of the calcined material did not regenerate significantly Bronsted acid sites, due to irreversible changes in the zeolite framework (51). 

Pyridine sorption studies on EDTA-dealuminated Y zeolites at various temperatures (54,58), as well as measurements of differential heats of adsorption of ammonia on aluminum-deficient Y zeolites (57,59) have led to the conclusion that aluminum-deficient Y zeolites have stronger acid sites than the parent zeolite. 

Numerous laboratory sorption studies have been conducted for the most common surfactants non-ionics, such as AE and alkylphenol ethox-ylates (APEOs) anionics such as LAS, secondary alkane sulfonates (SASs) and sodium dodecylsulfates (SDS) and on different natural sorbents [3,8,15-17], Until now, cationic and amphoteric surfactants have received less study than the other types, probably because they represent only 5 and 2%, respectively, of the total surfactant consumption in Western Europe (1998) [18]. 

Schwartzenbach, R. P. and Westhall, H., 1981, Transport of Nonpolar Organic Compounds from Surface Water to Groundwater, Laboratory Sorption Studies Environmental Science and Technology, Vol. 15, pp. 1350-1367. 

An important and significant task in sorption studies is the effort to identify the chemical form(s) of the sorbed metal ion. 

The experimental basis of sorption studies includes structural data (SANS, SAXS, USAXS), isopiestic vapor sorption isotherms,i and capillary isotherms, measured by the method of standard porosimetry. i 2-i44 Thermodynamic models for water uptake by vapor-equilibrated PEMs have been suggested by various groupThe models account for interfacial energies, elastic energies, and entropic contributions. They usually treat rate constants of interfacial water exchange and of bulk transport of water by diffusion and hydraulic permeation as empirical functions of temperature. 

A requirement for application of Equation 1, however, is that the polymer be uncrosslinked. Most vapor sorption studies on coal have been conducted on the covalently crosslinked portion of coals. Under this condition, simultaneous evaluation of x and M. must be made. Two groups of researchers have adopted this approach.(S 2) We have adopted an alternative approach by conducting vapor sorption studies on the uncrosslinked portion of the coal, x parameters can thus be directly calculated from the pressure-sorption data using Equation 1. 

SAMPLE PREPARATION. Dry Illinois No. 6 (Herrin seam, -60 mesh) was used in the sorption studies. Analysis Found C, 74.37 H, 4.83 N, 1.76 S, 1.76 O (by difference), 8.74 Ash, 8.33 (duplicate). Approximately 10 g of the sample was exhaustively Soxhlet extracted with pyridine. Extractability was 18.7% (wt). The pyridine solution was then filtered through a 0.4 /xm filter to insure removal of particulates and colloidal material. The filter did not plug. Most of the pyridine was removed by rotovaporization under reduced pressure at 70-80 C. Approximately 200 mL of a methanol/water (80/20 vol) mixture and 2 mL of cone. HCl were added to the flask and the mixture was stirred under nitrogen for two days. The solid extract was then filtered and dried under vacuum at 105 "C for 24 hours. Analysis Found C, 80.0 H, 5.64 N, 1.85 S, 0.70 Ash, 0.30 (duplicate). 

Mandjiny, S., Zouboulis, A. I. Matis, K. A. 1995. Removal of cadmium from dilute solutions by hydroxyapatite. I. sorption studies. Separation Science and Technology, 30, 2963-2978. 

Ziegler, F., Giere, R. Johnson, C. A. 2001a. The sorption mechanisms of zinc to calcium silicate hydrate Sorption studies and microscopic investigations. Environmental Science and Technology, 35, 4556-4561. 

It was necessary to prepare an aqueous electrolyte solution for the sorption study. To simulate sorption processes which occur in natural systems, the electrolyte solution should fulfill two criteria ... 

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