Preparation of SiO2/Si3N4 ceramics with step gradient porosity and heavy metal ion adsorption

Abstract Microporous ceramics with slag gradient distribution were prepared by interlayer bonding methods, using silicon dioxide and silicon nitride as the main raw materials. The material performances of gradient ceramics and uniform ceramics were discussed, and the adsorption effects of Cd (Ⅱ), Pb (Ⅱ) between them were compared. The experimental results show a flexural strength of gradient ceramics of 10.67 MPa, bonding strength of the bonding layer of 15.28 MPa, and only a 0.89% difference in the line shrinkage of the gradient layer of different slag contents, indicating that it is feasible to utilize interlayer bonding methods to prepare gradient ceramics. The maximum adsorption quantity of Cd (II), Pb (II) of gradient ceramics can reach 3.48 mg/g and 4.40 mg/g, respectively. For an average slag content of 17.5 wt%, gradient ceramics exhibited high permeability flux equivalent to ceramic with 25 wt% slag content and heavy metal adsorption amount equivalent to ceramic with 20 wt% slag content. Overall, the gradient ceramics prepared by interlayer bonding method can effectively improve the removal efficiency of adsorbent and the overall filtration efficiency.