Study On The Preparation Of Glass-ceramics Using A Waste Water Flocculate

The utilization of industrial solid wastes to prepare glass-ceramics can reduce thepressure of environmental protection on industrials and the production cost of glass-ceramics.A large quantity of waste water flocculate (WWF) is produced in the producer offluidized-bed catalytic cracking (FCC) catalysts. In this work, the composition andvitrification of a WWF were investigated. Other mineral raw materials were added to adjustthe properties of the prepared glass. Glass-ceramics with excellent performance were preparedvia sintering and bulk crystallization methods.XRF，DTA, XRD, SEM, IR etc. were used to test and analyse the WWF, glass andglass-ceramics. The influences of composition and preparation conditions on themicrostructure and physical, chemical properties of the products have been dissussed. Basedon a lot of experiments, the processing parameters were determined to make glass-ceramicswith the WWF have been optimized.Analysis shows that the WWF contains large amounts of SiO2, Al2O3and otheringredients, which can be used as raw materials for CaO-Al2O3-SiO2glass. Glass from pureWWF can be prepared in1350oC for2hours. The density and chemical stability of thesample is close to ordinary plate and container glass. However, the viscosity of the glass meltis too high, making the shaping impossible. In order to improve the workability of theglassmelt, some mineral materials such as limestone, dolomite, fluorite were added to adjustthe composition and viscosity characteristics of the glass. The influence of MgO contents onthe formation of glass has been emphasized. It is found that with the increase of MgO, thedensity of the glass increases, chemical stability and crystallization peak temperature decreaseand the tendency of phase separation and crystallization increase.Glass-ceramics with gehlenite as main crystalline phase can be successfully prepared bythe sintering method. The influences of binder, sintering temperature, soaking time, hatingrate, glass powder size, basic glass composition on the microstructure and properties of thesintered products have been discussed. Kaolin was chosed as a binder, and the optimumsintering conditions are as follows: glass powder sized smaller than75μm,4wt%of kaolin, heated to700oC at a rate of5oC/min, and then to900oC with a heating rate of3oC/min andsoaking for60min.Surface crystallization was the main crystallination mechanism of CaO-Al2O3-SiO2glasses. In order to obtain glass-ceramics via bulk crystallization, appropriate nucleating agentis necessary. In this experiment, the influence of TiO2, Cr2O3, P2O5and composite nucleatingagent on the crystallization of the sample were compared. The results revealed that the samplewith P2O5as a nucleating agent can achieve bulk crystallization and the crystal growth indexcan be larger than3. Optimized heat treatment process and parameters can effectively improvethe performance of the prepared glass-ceramics. The sample containing9%P2O5was firstheated to700°C,1h for nucleation and then to850°C for crystallization. The obtainedglass-ceramics is dense and uniform, with main crystalline phase of hydroxyapatite. The resultshows that P2O5not only plays a role as a nucleating agent but also becomes the composition ofthe crystal phase.The use ratio of this waste water flocculate exceeds55%, which can consume a lot ofsolid wastes and turn waste into treasure, at the same time, it protect the environment and hasgood social and economic benefits.