| The categories and amounts of pollution stuff have continuously increased as the economy and the society develop.Producing new filtration materials by solid wastes plays a significant role in environment-protection.This study used sintered red mud,Bayer red mud and East-lake sediments as the main raw materials to prepare excellent series porous ceramic filtration materials with some additives added to improve forming and sintering properties,which has carried out exploitation and utilization of varied solid wastes.The chemical compositions,crystal phases,high-temperature properties and microstructure of the solid wastes sintered red mud,Bayer red mud and East-lake sediments have been tested by XRFA,XRD,TG-DTA and SEM.The results indicated that sintered red mud was suitable to produce low temperature and fast firing Ca-Al-Si system ceramics,Bayer red mud was suitable to produce ceramics with high quality and a large amount of quartz(SiO2)existed in East-lake sediments could endue samples with higher strength and durability.The performances and microstructure of the porous ceramic filtration materials made by red mud were tested by SEM,XRD and EPMA.The results showed that porous ceramic filtration materials could be prepared by either of sintered red mud (S)or Bayer red mud(B),while usage of both two kinds of them was superior to that of either of them.The porosity(Pa)was 37.58%,water absorption(Wa)was 20.44%, bulk density(D)was 1.84kg/m3,crushing strength was 26.6MPa,acid resistance was 89.17%and alkali resistance was 99.76%,when the optimal sample BS5-2 was fired at 1100℃with 50 wt%total content of red mud in which S:B(sintered red mud to Bayer red mud)was 1:1.2.The low-temperature pore-forming material coal powder and the high-temperature pore-forming material graphite were added into the optimal sample BS5-2 to control the porosity and the corresponding performances of as-received samples were measured by SEM and XRD.The results showed that addition of the low-temperature pore-forming material coal powder and the high-temperature pore-forming material graphite could both contribute to control the porosity while the series with graphite added was superior to the other.The porosity(Pa)was 48.21%,water absorption(Wa)was 31.33%,bulk density(D)was 1.54kg/m3, crushing strength was 10.50MPa,acid resistance was 86.55%and alkali resistance was 97.87%,when the optimal sample G2 was fired at 1120℃with 20 wt% additional content of graphite added.The East-lake sediments were used to prepare porous ceramic filtration materials while the high-temperature pore-forming materials dolomite and graphite were added into the optimal sample made by East-lake sediments to control the porosity and the corresponding performances of as-received samples were measured by SEM and XRD.The results showed that addition of the pore-forming materials dolomite and graphite could both contribute to control the porosity while the series with graphite added was superior to the other.The porosity(Pa)was 36.97%,water absorption(Wa)was 20.34%,bulk density(D)was 1.82kg/m3,crushing strength was 13.50MPa,acid resistance was 96.76%and alkali resistance was 97.38%,when the optimal sample YC2 was fired at 1080℃with 20 wt%additional content of graphite added.The reaction mechanism of the porous ceramic filtration materials made by red mud was discussed in this study.It was found that varied crystal phases in raw materials produced liquid phase or solid phase in sintering process and the resultant of reaction depended on factors such as crystal phases of raw materials,sintered temperatures,reaction activity and sintered atmosphere.There was a tendency to generate mullite(3Al2O3·2SiO2)with clay added in the system.There was also a tendency to generate cordierite(2MgO·2Al2O3·5SiO2)with Bayer red mud added. The reaction mechanism in high temperature of this system corresponded to the rule of Mg-Ca-Al-Si system. |
