Liquid-phase adsorptions iodine adsorption

Liquid-phase adsorption methods are widely used for quaUty control and specification purposes. The adsorption of iodine from potassium iodide solution is the standard ASTM method D1510-83 (2). The surface area is expressed as the iodine number whose units are milligrams of iodine adsorbed per gram of carbon. It is quite fortuitous that the values of iodine numbers turn out to be about the same as the values for surface areas in square meters per gram by nitrogen adsorption for nonporous carbon blacks. 

The proportion of total soil iodine partitioning into the liquid phase of a soil is often considered to be low due to high levels of adsorption onto solid-phase components. For example, Johnson (1980) analyzed 183 soil samples from the United Kingdom and found that water-extractable values could be <0.1mg-kg representing <0.1% of total soil iodine. However, the full range of values for this set of soil samples extended to 13.6mg-kg in the liquid phase, equivalent to around 25% of total iodine. Similarly, Hou et al (2003) found that readily available (the most environmentally mobile) I (water-soluble and exchangeable fractions) accounted for around 20% of total I in Chernobyl soil and around 10% of total I in Irish Sea sediment (Figure 11.2). Therefore, appreciable quantities of iodine... 

The liquid-phase materials are usually characterized by sorption tests using phenol, iodine, or "molasses number." The vapor-phase activated carbons are usually characKiized by carbon tetrachloride or benzene adsorption tests. The adsorption capacity and the bulk density define the volumetric treatii capability of the material. 

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]. 

Figure 11.1 Schematic of potential transfers of iodine in the soil-plant-air system. Transfers, illustrated by arrows, between the solid, liquid and gas soil phases are (a) volatilization (b) dissolution (c) adsorption and (d) desorption and dissolution.

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