Fabrication of porous mullite‐based ceramic bricks from Al‐rich water treatment sludge and kaolinitic‐based clay

Abstract

A large quantity of water treatment sludge (WTS) is generated yearly from Ghana's Weija water treatment plant. The sludge contains some heavy metals and other toxic chemicals, which must be managed to minimize environmental impact. In the current work, WTS was mixed with varying quantities of kaolinitic-based clays (kaolin and lithomargic clays) to produce porous mullitebased bricks. The bricks were fired at 1200 • C for 1 h, and their properties were determined. Lithomargic clay-based mixtures had less dimensional variation and were suitable to produce near-net shape bricks compared to WTS-based bricks. The addition of WTS increased the linear firing shrinkage and apparent porosity whilst decreasing bulk density and compressive strength. Porous mullite-based bricks fabricated from lithomargic clay exhibited high compressive strength (6.3 MPa) at 10 wt.% WTS addition. The highest apparent porosity of 27% was attained at 40 wt.% WTS addition with compressive strength of 5.1 MPa and thermal conductivity of .5 W/m K.