Hypoxic preparation of solid wastes derived ceramsite for enhanced Cd(II) removal

Solid waste derived ceramsites are a typical representative of the "treat waste by waste" concept, however, they have not been given enough attention due to high energy consumption, large carbon emissions and low efficiency. In this work, a hypoxic roasting method was used to prepare industrial solid derived ceramsite for the removal of heavy metal Cd(II) from aqueous solution. Compared with conventional ceramsite (CC), the novel hypoxic ceramsite (HC) exhibited higher specific surface area, more hydroxyl and aromatic functional groups, and more developed pore structure. It could effectively adsorb Cd(II) from aqueous solution in a wide pH range of 2-8, and the adsorption rate was 3 times that of CC. The maximum adsorption capacities of Cd(II) by CC and HC were 22.9 and 32.2 mg/g at 25 °C respectively. The adsorption mechanisms included electrostatic interaction, hydrogen bond reaction and complexation reaction. After five regeneration cycles, the removal efficiency of HC maintained 86.9 %. Furthermore, about 60 % of carbon was retained in HC, largely reducing carbon emissions. These findings reveal the energy conversation and environmental friendliness of this ceramsite, which strongly supports the development and popularization of hypoxic preparation methods for ceramsites.