Silicon nitride (Si₃N₄) combines high mechanical strength with excellent thermal shock and corrosion resistance. Moreover, its elongated β-Si₃N₄ grains can provide abundant surface reactive sites. In this study, porous Si₃N₄ ceramics with low bulk density, high porosity, and high specific surface area (SSA) were fabricated via a gelcasting-assisted Pickering emulsion templating method. In this process, the Pickering emulsion was used to construct a microporous structure, while gelcasting shortened the preparation cycle and improved the mechanical integrity of the green bodies. The prepared ceramics were further applied to the adsorption and removal of malachite green (MG), a typical dye pollutant, from industrial wastewater. At a ceramic dosage of 100 g·L^-1, the porous Si₃N₄ ceramics achieved a removal efficiency of 98.9% for 100 mg·L^-1 MG within 12 h. In addition, the material exhibited excellent regeneration performance, maintaining a regeneration efficiency of 97.9% after three cycles. The adsorption process followed the pseudo-second-order kinetic model. The favorable adsorption performance was mainly attributed to hydrogen bonding, van der Waals interactions, and electrostatic attraction between the ceramic surface and MG molecules. These results indicate that porous Si₃N₄ ceramics have promising potential for filtration and adsorption applications.

Si₃N₄ porous ceramics possess light weight, high specific mechanical strength, excellent specific surface area, low thermal conductivity and low dielectric constant, making them to be promising candidates as high-temperature structural components, adsorbent, filters, catalyst supports, wave transparent materials, bio-scaffolds and so on. The comprehensive performance of Si₃N₄ porous ceramics is closely dependent on the processing. Herein, based on the design of raw materials, the fabrication of Si₃N₄ porous ceramics will be reviewed. Furthermore, the general pore-forming techniques for Si₃N₄ porous ceramics will be analyzed, thus providing guidelines for the microstructure design and performance regulation of Si₃N₄ porous ceramics.