Sodium borosilicate glass, leaching

The slow rate of dissolution of, or leaching from, durable glasses has led to proposals for the vitrification of nuclear waste. Glasses based on the sodium borosilicate system appear to be favoured because of their ability to dissolve the waste, combined with good chemical durability. Intensive development has taken place over recent ycars and a regular journal is devoted to this topic . 

Figure 2. SIMS depth profiles for a sodium borosilicate glass blank sample, air-exposed only (a), and sample exposed to aqueous leaching at 25°C for 30 min (b).

Figure 3. Comparison of SIMS depth profiles of aqueous leaching of a sodium borosilicate glass, for 30 min (a). Key ----------, 0°C and--------, 25°C. Error func-...

Patents [102, 103] describe the preparation of open tubular columns with an inside thickness-fixed porous layer by etching. First, the authors prepared a capillary column from a two-layer workpiece composed of two concentric tubes, one of them (external) being made of sodium borosilicate glass. To obtain an adsorption layer of defined thickness, the inner layer of the two-layer capillary was entirely leached. The method relies on porous glasses as the adsorbents. Porous glasses have been successfully used in gas capillary (see, for example, [104]). 

Figure 6.8 Na (by RBS) and H (by ERD) depth profiles of the surfaces of a sodium borosilicate glass leached in a pH 8 aqueous solution at 70 °C for various times. (From Reference 25.)...

Figure 2 shows the predicted, normalized cumulative mass losses based on the behaviors of silicon and sodium for three different values of the leachant renewal frequency. The physical parameters used refer to the leaching of PNL 76 68 borosilicate glass in deionized water at 90°C, (4) and reference is made to the geometric surface area, SA, of the sample. In particular, the curves corresponding to silicon and sodium tend to have the same, constant slope with increasing flow rate. In particular, the curves corresponding to = 1 day 1 practically coincide, indicative of network dissolution control. 

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