Filter Paper, Adsorption

A less specific type of adsorption can sometimes be used if the required product forms insoluble hydroxides but the target element does not. In this case, the solution is made alkaline, and the carrier-free radio-colloidal product is readily absorbed on to filter paper in good yield, when, after washing, it can subsequently be dissolved in acid. This has been used for the separation of magnesium from aluminium, scandium from calcium and for several other elements (17), (26), (42), (44), (66), (103), (104), (105), (106). 

Batch adsorption tests were done at five different particle sizes 300, 425, 600, 710 and 850 pm. 0.1 g of the sumac leaves was weighed and 8 ttiL of ion solution was added. The volume was completed 50 ttiL. After stirring 2 h, the reaction mixtures were filtered through a filter paper to remove particulates and the filtrate was analyzed with an AAS. 

Phosphate must be applied as fertilizer to the soil. Ideally it is added in quantities sufficient to guarantee optimal yields, but not in excess in order to avoid P transportation into other compartments of the ecosystem. The amount added should be based on an accurate estimation of the plant-available fraction of P already present in a soil.This is an old and difficult task and a large number of extraction methods have been used since intensive land use was practised. Recently methods have been worked out in which a strip of filter paper impregnated with an Fe oxide (2-line ferri-hydrite) is dipped into a soil suspension and the amount of P adsorbed by the paper is taken as being plant-available (Sissingh,1988 Van der Zee et ah, 1987 Sharpley, 1993 Sharpley et ah,1994 Kuo and Jellum, 1994 Myers et ah 1997). Anion and cation resins extracted more P from four heavily fertilized soils than from goethite (Delgado Torrent, 2000). Other oxyanions adsorbed by soil Fe oxides are silicate, arsenate, chromate, selenite ( ) and sulphate. Adsorption of sulphate led to a release of OH ions and was substantially lowered once the Fe oxides were selectively removed (Fig.16.17). 

C. Paper Chromatography(Papyrography or Partography). In this method, filter paper is used as an adsorbent in lieu of materials used in chromatographic columns. Although the principle of selective adsorption by paper (such as papyrus) was known for centuries and... 

Errors occur in transfer of the two solutions, to glassware, on the filter paper, on washing, on heating, on transfer to and on the balance including adsorption effects of moisture or C02, perhaps forming Sr(OH)2 or... 

Figure 2. The effect of PEG-modification on the lignin model compound, dehydro-diisoeugenol (dimer). Solvent = acetonitrile, t =0 is the brightness recorded immediately after adsorption of compound on filter paper. The brightness of untreated filter paper is 80.1%. (Cole, B.J.W. Huth, S.P. Runnels, P.S., /. Wood Chem. Technol., in press.)...

In gravimetric analysis, definite crystalline precipitates are desired and the procedure thus adopted aims to get sufficiently bigger particles, because extremely small particles may pass through the filter paper. To prevent adsorption of the undesirable molecules with the desired precipitate, it is necessary to precipitate the solution at the boiling point and fairly dilute solution should be used. 

The term reactive filtration may be used in a variety of applications. A simple search of the internet provides results such as reactive filter paper [1], adsorption filters for removing heavy metals from water [2], solid matrices used in organic synthesis [3], membranes for wastewater treatment, or even dialysis machines, filters for deep-frying pans and devices for the dechlorination of shower water by reaction with vitamin C. Most of the applications termed reactive filtration would be named heterogeneous catalysis or adsorption from a chemical engineer s point of view. 

A. Place about 3 g of powdered sample in a glass-stoppered Erlenmeyer flask containing 10 mL of dilute hydrochloric acid (5%), boil for 30 s, and cool to room temperature. Add 100 mL of iodine TS, stopper, and shake vigorously for 30 s. Filter through Whatman No. 2 filter paper, or equivalent, discarding the first portion of filtrate. Compare 50 mL of the subsequent filtrate with a reference solution prepared by diluting 10 mL of iodine TS to 50 mL with water, but not treated with carbon. The color of the carbon-treated iodine solution is no darker than that of the reference solution, indicating the adsorptivity of the sample. 

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