| Bauxite tailings are a type of industrial waste residue produced during the process of bauxite exploitation and mill run.With the continual development of the national economy,the consumption of bauxites is being increased year and year during the recent years,the capacity of aluminum production companies has continuously expanded and a large number of the bauxite tailings are stockpiled,which has brought environmental pollution,land appropriation and even safety problem.Therefore,it is certainly necessary to find more available methods for the utilization of bauxite tailings,in order that the integrated utilization problem of bauxite tailings can be solved reasonably.The porous ceramic sample was prepared by using bauxite tailings as the bone material of porous ceramic and the process of adding pore-forming agents in this paper.The influences of the multi-factors such as the particle granularity of bauxite tailings,the category and capacity of pore-forming agents,sintering temperatures,molding pressures,temperature preservation times and sintering additive etc on bending strength,apparent porosity,water absorption and volume density of porous ceramic sample made by bauxite tailings were researched.The main research contents are as follows:1.Testing of the performances of bauxite tailings.The performances of bauxite tailings were tested by using D/Max-2200 X-Ray Diffractometer,NETZSCH STA449F3 Synchronous Thermal Analyzer,LS603 Laser Particle Size Tester and GYS-2 Photoelectric Liquid Plastic Limit Joint Meter etc.The testing results showed that,the main mineral compositions of bauxite tailings were Al2O3,SiO2 and Fe2O3,the average particle granularity size of bauxite tailings was 60.88?m,the plasticity index of bauxite tailings was 16.3,bauxite tailings had better plasticity and sintering suitable for the preparation of porous ceramic.2.Selection of pore-forming agents and sintering additives.Carbon powder,graphite powder,starch and sodium bicarbonate were originally selected as the four types of pore-forming agents,the performances of porous ceramic sample prepared by the four types of pore-forming agents added with different capacities were tested.The experimental testing results showed that,with the increase of the added capacity of the four types of pore-forming agents,the apparent porosity and water absorption of porous ceramic sample were gradually increased,but the bending strength and volume density of porous ceramic sample were decreased.After the integrated consideration of various performance indexes,carbon powder was finally selected as the pore-forming agent,at the same time sodium dihydrogen phosphate was also selected as a sintering additive in order to enhance the bending strength and maintain the apparent porosity.3.Selection of sintering temperatures,molding pressures and temperature preservation times.The performances of the porous ceramic sample prepared by different sintering temperatures,molding pressures and temperature preservation times as well as carbon powder selected as the pore-forming agent were tested,the testing results showed that,along with the increase of sintering temperature,molding pressure and temperature preservation time,the bending strength and the volume density were increased while the apparent porosity and the water absorption were decreased,in which its sintering temperature range was 1050°C-1200°C,the optimal molding pressure was 9MPa and the optimum temperature preservation time was 60 min.4.Analyses of crystal phase structures and microstructures of the porous ceramic sample.The crystal phase structures and microstructures of the porous ceramic sample prepared by bauxite tailings were tested and analyzed by using D/Max-2200 X-Ray Diffractometer and VEGA 3 SBU Scanning Electron Microscopy.The testing and analysis results showed that,the main crystal phases were corundum and quartz,and small capacities of phases were hematite and sodium salt.The cross section SEM morphology analysis results showed that,the micro-pores in the porous ceramic sample were plentiful,and the porous ceramic sample had higher specific surface area whose distribution was uniform,and good connectivity to each other.5.Research on the optimal prescriptions and technical parameters of the porous ceramic as well as the relationship between its bending strength and apparent porosity.The performances of the porous ceramic sample prepared by different sintering temperatures,and different addition capacities of carbon powder under the determined process conditions were researched by using TYA-100C Electro-hydraulic Bending Test Machine and the boiling method.The experimental research results showed that,the main factors influenced the performances of the porous ceramic sample were firstly sintering temperature and adding capacity of carbon powder,and secondly the adding capacity of sodium dihydrogen phosphate,temperature preservation time,molding pressure and granularity size.The optimum prescriptions and technical parameters were respectively like that:the distribution of granularity size was 61?m-75?m,and the mixture moisture was 13%,the adding capacity of carbon powder was 18%,the capacity of sodium dihydrogen phosphate was 16%,the capacity of bentonite was 10%,the sintering temperature was 1100°C,the molding pressure was 9 MPa,the temperature preservation time was 60 min.Based on these conditions,the porous ceramic sample was prepared with the apparent porosity of 50.54%,the bending strength of 16.83 MPa,the water absorption of 40.33%and the volume density of 1.12 g/cm3.The relationship between the bending strength and the apparent porosity was obtained by using the measured experimental data and related software.The research work and achievements in this paper can provide a new approach for the integrated utilization of bauxite tailings,and effectively solve the problem of the lower utilization degree of bauxite tailings,which will afford comparatively reliable experiment evidence and technical foundations for the preparation of porous ceramics made by bauxite tailings. |
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