The recovery of Zn and Pb and the manufacture of lightweight bricks from zinc smelting slag and clay

Novel lightweight bricks have been produced by sintering mixes of zinc smelting slag and clay. A two-stage sintered process has been proposed to recovery of Zn and Pb and reutilization of the zinc smelting slag. In the first stage of the process, called reduction and volatilization procedure, zinc and lead were reduced by the carbon contained in the zinc smelting slag and volatilized into the dust, and the dust can be used as a secondary zinc resource. In the second stage of the process, called oxidation sintering procedure, a lightweight brick was produced. Samples containing up to 60 wt.% zinc smelting slag and 40 wt.% kaolin clay were reduced at 1050 °C for 6 h, and then sintered at 1050 °C for 4 h. The recoveries of Zn and Pb from the brick are 94.5 ± 0.6% and 97.6 ± 0.2%, respectively. Low bulk density (1.42 g cm−3) and relatively high compressive strength (22 MPa) sintered bricks were produced, and the leaching toxicity of the sintered bricks was below the regulatory thresholds of Chinese National Standards.