Iodine adsorption test methods

Table 2.7 lists techniques used to characterise carbon-blacks. Analysis of CB in rubber vulcanisates requires recovery of CB by digestion of the matrix followed by filtration, or by nonoxidative pyrolysis. Dispersion of CB within rubber products is usually assessed by the Cabot dispersion test, or by means of TEM. Kruse [46] has reviewed rubber microscopy, including the determination of the microstructure of CB in rubber compounds and vulcanisates and their qualitative and quantitative determination. Analysis of free CB features measurements of (i) particulate and aggregate size (SEM, TEM, XRD, AFM, STM) (ii) total surface area according to the BET method (ISO 4652), iodine adsorption (ISO 1304) or cetyltrimethylammonium bromide (CTAB) adsorption (ASTM D 3765) and (iii) external surface area, according to the dibutylphthalate (DBP) test (ASTM D 2414). TGA is an excellent technique for the quantification of CB in rubbers. However, it is very limited in being able to distinguish the different types of... 

The yields of A-fraction by the above method are substantially higher than the 22-23% previously reported by butyl alcohol fractionation, since the latter method does not give as complete a separation. From the iodine adsorption of raw corn starch and of the purified A-fraction, Bates, French and Rundle have calculated the content of A-fraction in corn starch as 22%. This low value is due to the use of incompletely defatted starch, and its agreement with the yield by butyl alcohol precipitation is purely coincidental. Under preferred methods of testing, exhaustively defatted corn starch adsorbs 5.3% iodine. Dividing this latter value by the 19.0% iodine adsorption for the recrystallized A-fraction, a theoretical content of 28% is calculated for corn starch, in agreement with the yields by Pentasol fractionation. 

No satisfactory method has been found for removing the 3-4% of A-fraction presumably remaining in the Pentasol non-precipitated B-traction. Bates, French and Rundle have suggested that this may be removed by repeated treatment with cotton. Attempts to apply this purification have not been successful. Various grades of cotton, cellulose pulp, charcoal, activated alumina, precipitated aluminum hydroxide, bentonite and fuller s earth have been tested, without any significant improvement in the purity of the B-fraction. It is possible that Bundle s cotton treatment may introduce traces of lipid material (fatty acids or sterols) which mask the iodine adsorption. 

Iodine adsorption it is a simple and quick test, giving an indication of the internal surface area of the carbon in many activated carbons the iodine number (expressed as milligrams of iodine per gram of carbon) is close to the Brunauer-Emmett-Teller (BET) surface area. In this method, the activated carbon is boiled with 5% HCl and, after cooling, a 0.1N iodine solution is added and shaken for 30 s after filtration, the filtrate is titrated with O.IN sodium thiosulfate solution, with starch as indicator. The standard used is AWWA B600-78 (see Section 8.1.2). 

Standard test method for carbon black-iodine adsorption number. 

P rowicz J., Walfga E. PN-83/C-97555.04. Activated carbon. Method of test. Determination of adsorption value of iodine. 

Liquid-phase adsorption methods are also widely used. The adsorption of iodine from potassium iodide solution is the standard ASTM method D1510. The surface area is expressed as the iodine number whose imits are milligrams of iodine adsorbed per gram of carbon blacks. The test conditions such as adsorbate concentration and the amount of carbon black sample used are specified in such a way that the values of iodine numbers turn out to be about the same as the values for surface areas in square meters per gram that is measured by nitrogen adsorption for nonporous and nonoxidized furnace carbon blacks. The iodine number is raised by porosity and decreased by surface oxygen or adsorbed organics. Still it is the most easily measured surface area estimate and is used extensively, especially for process control. 

The selection of the AC for a given application (solutes to be retained, concentration, stream flow, etc.) is made by dynamic tests in pilot adsorption units. However, it is more effectively done, with less time consumption, if the adsorption properties of the candidates are established. Properties such as the surface area and PSD, iodine number, bulk density, particle size, hardness and mechanical strength give an idea of the suitability of the AC. The determination of the adsorption isotherm of a given solute over a wide range of concentrations is the method to obtain the equihbrium capacity of the adsorbent. In this way, the amount of solute it can remove from the solution can be estimated and consequently the suitability of the AC for achieving the required removal of the solute. 

In this work, an adsorption method as a technique of collection in liquid phase, and a vitrification method of iodine toward safekeeping were studied. Here, several kinds of MgO and Mg(OH)2 with different surface areas were tested as adsorbent magnesium compounds for simulated radioactive iodine. Magnesium compounds were reported to be able to adsorb not only iodine physically, but also chemically (as iodide, iodate, etc.) [1]. 

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