Abstract:

Porous SiC ceramics with different mass fractions of Y₂O₃ （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 Y₂SiO₇ and Y₅Si₃C_0.5 increases with the increase of Y₂O₃ 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 2.5 μm. As the increase of Y₂O₃ 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/cm³ with a Y₂O₃ content of 6%， and the thermal conductivity increases first and then decreases with the increase of the Y₂O₃ content. The filtration test of metal Cd²⁺ in the wastwater shows that with the increase of Y₂O₃ content， the residual concentration， the trend of the membrane flux of SiC thin film， and the removal rate of Cd²⁺ first decrease and then increase. When the doping concentration is 4%， the minimum residual mass concentration of Cd²⁺ 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 Cd²⁺ gradually decreases and the removal rate gradually increases， and both stabilize under alkaline conditions when pH ≥9. On the whole， the best content of Y₂O₃ for porous SiC ceramics is 4%.

Key words: Silicon carbide, Micro-oxidation sintering, Ceramics, Sintering aid, Y₂O₃, pH, Wastewater treatment