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Since the glass is matastable from the viewpoint of thermodynamics, the highlevel liquid waste glass may crystallize during the process of production, storage, and disposal. Borosilicate glass is used as the matrix for immobilization of highlevel liquid waste in China. It is worth noting that pyroxene phase is easy to crystallize in borosilicate waste glass. In order to suppress the crystallization of pyroxene phase, it was proposed that MgO and CaO in the borosilicate glass formula were partially replaced by P2O5 in this study. The effect of P2O5 content (mass fraction of 08%) on the crystallization characteristics and leaching resistance of borosilicate waste glass was mainly investigated. The results show that the waste glass possesses amorphous phase when the content of P2O5 is 03%. For the samples after heating at 850 ℃ for 6 h, the main crystalline phases are pyroxene when P2O5 content is 02%. In addition, a small amount of calcium silicate phase appears for the heat treated samples with 3% P2O5 content, and pyroxene phase almost disappears. When the content of P2O5 is higher than 3%, spherical Na3Ca6(PO4)5 crystals precipitate in the glass, and the crystallinity increases with P2O5 content. The analyses of 29Si and 11B MAS NMR show that with the increase of P2O5 content from 0 to 6%, the total content of Q3 and Q4 structural units in the glass network gradually increase from 5304% to 8356%, and the content of BO3 structural units increases from 2943% to 3822%. The increase of P2O5 content improves the densification of the overall network structure of the waste glass. The results of the static leaching method (MCC1) show that the normalized leaching rates LRSi, LRB, LRNa and LRCs of the waste glasses gradually decrease with the increase of P2O5 content. After 28 d, LRSi, LRB, LRNa and LRCs of the waste glass with 3% P2O5 content are 0508, 0468, 0533 and 0280 g/(m2·d), respectively, which can satisfy the requirements ( |
