微氧化烧结制备掺杂Y_(2)O_(3)的SiC陶瓷及含镉模拟废水处理

Preparation of Y_(2)O_(3)-Dopped SiC Ceramics by Micro-oxidation Sintering and Removal of Cd^(2+) in Mimic Wastewater

采用了微氧化烧结制备了不同Y_(2)O_(3)质量分数(0%、2%、4%、6%)的多孔SiC陶瓷,通过对陶瓷的晶体结构、微观形貌、物理性能和Cd^(2+)的去除率测试发现:添加了Y_(2)O_(3)的SiC陶瓷出现了较多的第二相Y_(2)SiO_(7)、Y_(5)Si_(3)C_(0.5),随着Y_(2)O_(3)的质量分数增加逐渐升高,主相的衍射峰的强度有降低。扫描电子显微镜测试发现,SiC陶瓷的尺寸在2.5μm,Y_(2)O_(3)引入后,SiC陶瓷的晶粒尺寸降低,高温烧结时液相的含量增加,熔体粘度降低,晶粒结合更加紧密,Y_(2)O_(3)的引入提高了多孔陶瓷的体积密度,Y_(2)O_(3)质量分数为6%SiC的体积密度最大为2.21 g/cm^(3)。热导率随着Y_(2)O_(3)质量分数的增加呈现出先升高后降低的趋势。金属Cd^(2+)的过滤测试表明:随着Y_(2)O_(3)质量分数增加,Cd^(2+)的残留质量浓度、膜通量和去除率先降低后升高,当掺杂质量分数为4%时,Cd^(2+)残留质量浓度最低为0.042 mg/L,膜通量达到了最大值572 L/(m2·h),去除率最大为99.95%,相比未掺质量分数杂体系的去除率提高了0.14%。随着溶液pH值的逐渐增大,金属Cd^(2+)的残留质量浓度逐渐降低、去除率逐渐升高,pH≥9时最终均趋于稳定。综合来看,多孔SiC陶瓷的助烧剂Y_(2)O_(3)最佳掺量为4%。

Porous SiC ceramics with different mass fractions of Y_(2)O_(3)(0%,2%,4%,6%)were prepared by micro-oxidation sintering.The crystal structure,micro morphology,physical properties and metal Cd removal rate of the ceramic were characterized.The second phases Y_(2)SiO_(7) and Y_(5)Si_(3)C_(0.5) increases with the increase of Y_(2)O_(3) content,and the intensity of the diffraction peaks of the main phase decreases.Scanning electron microscopy analysis shows that the size of SiC ceramics is 2.5μm.As the increase of Y_(2)O_(3) content,the grain size of SiC ceramics is reduced,the content of liquid phase increases during high-temperature sintering,the melt viscosity is reduced,and the crystal grains are more tightly bonded.Considering the bulk density of porous ceramics,the maximum bulk density of SiC is 2.21 g/cm^(3) with a Y_(2)O_(3) content of 6%,and the thermal conductivity increases first and then decreases with the increase of the Y_(2)O_(3) content.The filtration test of metal Cd^(2+)in the wastwater shows that with the increase of Y_(2)O_(3) content,the residual concentration,the trend of the membrane flux of SiC thin film,and the removal rate of Cd^(2+)first decrease and then increase.When the doping concentration is 4%,the minimum residual mass concentration of Cd^(2+)is 0.042 mg/L,the maximum membrane flux is 572 L/(m2·h),and the maximum removal rate is 99.95%,compared with the undoped system,the removal rate is increased by 0.14%.As the pH of the solution gradually increases,the residual concentration of metal Cd^(2+)gradually decreases and the removal rate gradually increases,and both stabilize under alkaline conditions when pH≥9.On the whole,the best content of Y_(2)O_(3) for porous SiC ceramics is 4%.