China's Refractories

Abstract: The recycling of waste activated carbon is of great significance in environmental protection. Porous mullite ceramics were prepared by impregnating the mullite precursor with activated carbon, adding a pore-forming agent, and adopting aluminum sulfate octahydrate, ammonia and silica micropowder as raw materials, waste activated carbon after heat treatment as the pore-forming agent, and sodium polyacrylate (PAAS) as the dispersant. The effects of the activated carbon additions (1.5%, 3.0%, 5.2%, and 7.8%, by mass) and PAAS additions (1%, 2%, and 3%, extra adding, by mass) on the physical properties, phase composition and microstructure of the porous ceramics were studied. The results show that: (1) as a pore-forming agent, activated carbon promotes the formation of pores inside the samples, while the apparent porosity of the samples increases significantly with the increasing activated carbon addition; when the activated carbon addition is 7.8%, the apparent porosity of the sample is 65.7%, the cold compressive strength is 4.62 MPa, the peak pore size is around 3.5 μm, and the pore size distribution is uniform; (2) appropriate PAAS helps to improve the dispersion of activated carbon in the samples and the comprehensive performance of the porous mullite ceramics; when the PAAS addition is 2%, the apparent porosity of the sample is 71.8%, the cold compressive strength is 5.53 MPa, the peak pore size is around 3 μm, and the pore size distribution is optimized; however, excessive PAAS increases the liquid phase in the system, resulting in over sintering of mullite and a decrease in the porosity.

Key words: waste activated carbon, porous mullite ceramics, impregnating precursor, dispersant