Recycling of harmful waste lead-zinc mine tailings and fly ash for preparation of inorganic porous ceramics

The porous ceramics were prepared by directly sintering of lead-zinc mine tailings and fly ash as the raw materials without any additional sintering and foaming agent. The effects of fly ash addition on the crystalline phases, pore structure, physical-chemical porosities and mechanical strength were investigated. The results showed that the bulk density decreased firstly and then increased while the porosity and water absorption presented the opposite tendency with the increase of fly ash content. Meanwhile, the chemical stability improved and the flexural strength had the same variation tendency of the bulk density. The phase evolution of sample with 60 wt% fly ash addition indicated that anorthite phase was formed at low temperature (1000 °C). The thermal behavior illustrated that the foaming process was initiated by the reaction of internal constituents in the lead-zinc mine tailings. Different pore structures indicated different foaming mechanisms that probably occurred at different temperatures. The porous ceramics with 60 wt% fly ash addition exhibited excellent properties, including bulk density of 0.93 g/cm3, porosity of 65.6%, and flexural strength of 11.9 MPa.