Ion-exchangers silicates

Methanol Conversion over Copper Ion-Exchanged Silicate Minerals"... 

T1 Ion-exchange Silicate rocks, marine sediments, sea water Fluorimetry, neutron activation 0.1 ppm 151)... 

Metals Ion-exchange Silicate rocks Different methods ppm-Range 177, 178)... 

Physical Properties. Physical properties of importance include particle size, density, volume fraction of intraparticle and extraparticle voids when packed into adsorbent beds, strength, attrition resistance, and dustiness. These properties can be varied intentionally to tailor adsorbents to specific apphcations (See Adsorption liquid separation Aluminum compounds, aluminum oxide (alumna) Carbon, activated carbon Ion exchange Molecular sieves and Silicon compounds, synthetic inorganic silicates). 

Greensands Naturally occurring materials, composed primarily of complex silicates, which possess ion-exchange properties. 

Voids The space between the resinous particles in an ion-exchange bed. Zeolite Naturally occurring hydrous silicates exhibiting limited base exchange. 

Engelhard s in-situ FCC catalyst technology is mainly based on growing zeolite within the kaolin-based particles as shown in Figure 3-9A. The aqueous solution of various kaolins is spray dried to form micR)spheres. The microspheres are hardened in a high-temperature l,3f)(TF/704°C) calcination process. The NaY zeolite is produced by digestion of the microspheres, which contain metakaolin, and mullite with caustic or sodium silicate. Simultaneously, an active matrix is formed with the microspheres. The crystallized microspheres are filtered and washed prior to ion exchange and any final treatment. 

The most important minerals of the lanthanide elements are monazite (phosphates of La, Ce, Pr, Nd and Sm, as well as thorium oxide) plus cerite and gadolinite (silicates of these elements). Separation is difficult because of the chemical similarity of the lanthanides. Fractional crystallization, complex formation, and selective adsorption and elution using an ion exchange resin (chromatography) are the most successful methods. 

Zeolites are naturally occurring hydrous aluminum-sodium silicates in porous granule form. They are capable of exchanging their sodium base for calcium or magnesium and of expelling these alkaline earth metals for sodium by treatment with salt. Thus, they are a type of ion-exchange media. (Some zeolites act as molecular sieves by adsorption of water and polar compounds.)... 

A natural ion-exchange material used for softening water and other purposes. Typically minerals of hydrated aluminum or sodium silicates. 

The measured potential is thus a linear function of pH an extremely wide (10-14 decades) linear range is obtained, with calibration plots yielding a slope of 59 mV per pH unit. The overall mechanism of the response is complex. The selective response is attributed to the ion-exchange properties of the glass surface, and in particular the replacement of sodium ions associated with the silicate groups in the glass by protons ... 

Kuhn Jones (1982) examined various models for fluoride release and showed that release did not fit the membrane and homogenous monolith model. Instead, they concluded that the cement behaved as a porous granular monolith, as described by Kydonieus (1980). The release of fluoride appears to be an ion exchange phenomenon, as dental silicate cement takes up rather than releases fluoride from solution if it is present in sufficient concentration (Kuhn, Lesan Setchell, 1983). 

Adsorption (including both physical adsorption and ion exchange) by clay minerals and silicates... 

The higher intensities /3 measured for ion exchanged gels (gels prepared by procedure b) comparing to /3 of gels prepared by procedure a, are probably the result of the different silica source used. It was found that gels prepared from sodium silicate contain... 

The category of builders consists predominantly of several types of materials -specific precipitating alkaline materials such as sodium carbonate and sodium silicate complexing agents like sodium triphosphate or nitrilotriacetic acid (NTA) and ion exchangers, such as water-soluble polycarboxylic acids and zeolites (e.g., zeolite A). 

As mentioned in the historical synopsis (Section 5.1), Levine121 perfected the compendial partition column procedure in which aspirin in chloroform is first trapped in an immobile phase of sodium bicarbonate on a column of siliceous earth (celite) then eluted with a solution of acetic acid in chloroform and measured spectrophotometrically. This has been also used for separation in combination products.80 For the determination of salicylic acid in presence of aspirin by this method, see Section 5.61. Ion exchange columns filled with strongly or weakly basic anion exchange resin in the acetate or chloride cycle have also been used for separation of aspirin in combination products. 122 123/l2lf This has also been adapted for a student experiment.125 A Sepha-dex-G25 column has been used for the separation of aspirin from salicylic acid.126... 

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