Study On The Structure And Property Of Iron Borophosphate Glass-ceramic Wasteforms

In this paper, the effect of Cr₂O₃ and ZrO₂ on the structure and resistance to divitrification property of the basic glass36Fe₂O₃-10B₂O₃-54P₂O₅?mol%? is investigated firstly, then monazite iron borophosphate glass-ceramic wasteforms which have the good chemical durability were prepared through controlled heat treatment for crystallization. In order to understanding the structure, phases and surface microstructure, the glass-ceramic samples were examined by XRD, FTIR, Raman and SEM-EDS. And the chemical durability was examined by MCC-1 leaching experiment. Here are main conclusions were summarized as follows:?1? Effect of Cr₂O₃ on the structure and properties of the iron borophosphate glass?glass-ceramic? shown that: Cr₂O₃ shows weak glass forming ability and has strong ability to make the36Fe₂O₃-10B₂O₃-54P₂O₅ glass crystallize, when the content of Cr₂O₃ is more than 1.0 wt.%, the ?-Cr PO₄ and Fe2?HPO₃?₃-based glass-ceramic was made. The structure of the studied Cr₂O₃-doped iron borophosphate glasses predominantly consists of orthophosphate?Q⁰? units and pyrophosphate?Q¹? units along with [BO₄] units. And with the increase of Cr₂O₃, Q⁰ units gradually transform to Q¹ units. The glass transition temperature is improved by Cr₂O₃ doping in the glass forming range.From the annealed samples, which annealed at 650°C⁸50°C, it can be concluded that the main crystalline phases are Fe2?HPO₃?₃,Fe PO₄?H₂O?₂ and Fe PO₄. And Cr₂O₃ promotes the crystallization of Fe2?HPO₃?₃, but restrain Fe PO₄?H₂O?₂ or Fe PO₄ crystallized from the glass.?2? 6mol% ZrO₂ can be immobilized in the36Fe₂O₃-10B₂O₃-54P₂O₅ glass. Partial crystallization occurs in the glasses doping with more than 6 mol% ZrO₂, and the main precipitated phase is Zr P₂O₇. The main structure units of the prepared glasses/glass-ceramics are also orthophosphate?Q⁰? units and pyrophosphate?Q¹? units along with [BO₄] units. Moreover, Zr-O-P bonds are formed, with the addition of ZrO₂, ZrO₂ enhances the strength of the glass network. From the samples annealed at 650°C⁸50°C, the main crystalline phases are Fe4?PO₄?2O, Zr P₂O₇ and Fe PO₄. And ZrO₂ promotes the crystallization of the glass to produce Zr P₂O₇ and Fe PO₄.?3? The 36Fe₂O₃-10B₂O₃-54P₂O₅ glass can immobilize 60 wt.%the designed wastes, and the main crystal phase is monazite and the main structure units of glass-ceramic wasteforms are orthophosphate?Q⁰? units, along with many O-Me-O-P bonds?Me represent metal cations?, which improve the chemical durability of wasteforms. The dissolution rate of the glass-ceramic wasteforms is 10-8¹0-9g/cm2·min,and decrease gradually with the time going on, and the leaching rate of the ion Al³⁺is about 1?g/ml, but La³⁺and Ce⁴⁺is under 0.005?g/ml,which indicates the iron borophosphate glass-ceramic wasteforms samples have good chemical durability, and the glass-ceramic samples immobilized 60 wt.% the designed wastes are excellent chemical durable.