| Chromium slag is a kind of poisonous solid waste. It not only does harm to people's health but also pollutes the ecological environment seriously. The pollution brought by chromium slag is arousing high attention of national environmental protection department, so it is very urgent to deal with the pollution of chromium slag. In addition to Cr2O3 and the poisonous water-solubility Cr6+ ion, the chromium slag contains a great deal of calcium oxide, magnesia, alumina and silica, which are useful compositions of glass-ceramics. Furthermore, Cr2O3 is an effective nucleating agent in the glass system. So it is a promising method to realize the detoxification and the resourceful utilization of chromium slag to prepare glass-ceramics by using chromium slag. Besides chromium slag and blast-furnace slag (two kind of industrial residue), quartz, dolomite, calcite, and talcum were also used as raw materials. SiC was used as reductant. The slag glass-ceramics was prepared by melting method. The effects of the content of chromium slag and diffirent CaO/MgO ratio on the melting performance, the major crystalline and the material properties were discussed. The mechanism of Cr6+ detoxification under high temperature was studied. When the content of chromium slag in the batch was 3050wt%, the flowing property of the melted glass was good. There is hardly no scruff and the glass was transparency. When the content of chromium slag was 55%, there was a lot scruff on the melted glass and the glass was opaque after moulding. When the content of chromium slag was 58%, there was yellow matter suspended on the melted glass, which is K3Na(CrO4)2 identified by XRD. In order to obtain the different CaO/MgO ratio, both chromium slag and blast-furnace slag were used in the glasses. With the CaO/MgO ratio changed, the crystallization temperature of glass, the main crystalline, the activation energy, the density, bending strength and microhardness of glass-ceramics were all changed. When the content of chromium slag was 40wt% and 45wt%, the major crystalline of the glass-ceramics was diopside (CaMg(SiO)3)2, and magnesiochromite (MgCr2O4); when the content of chromium slag increased to 50wt%, the major crystalline of glass-ceramics was diopside, and melilite((Ca1.53Na0.51)(Mg0.39Al0.41Fe0.16)(Si2O7)). The concentration of residual Cr6+ ion in specimens was determined by diphenylcarbazide(DPC) spectrophotom. When the content of chromium slag was between 4050wt%, the concentration of residual Cr6+ ion in the samples was 00.4mg/L, which is lower than the national standard of 0.5mg/L for vent. When the content of chromium slag was above 50wt%, the concentration of residual Cr6+ ion in the sample was higher than the national standard.
|
PDF Full Text Request