Preparation of the high-quality ceramsite from red mud and industrial solid wastes for Pb(II) adsorption from wastewater

High-quality ceramsite is prepared from solid waste (red mud, phosphogypsum, copper slag and poplar sawdust), and subsequently modified with nitric acid for removal of Pb
2+
from wastewater. The microstructure and phase composition of the ceramsite before and after modification are systematically characterized, and the corresponding Pb
2
⁺ adsorption performance is thoroughly investigated. Characterization analysis reveals that modification ceramsite possesses a well-developed pore structure and abundant surface functional groups with specific surface area of 50.68 m
2
/g, which is larger than original ceramsite. Pb
2+
adsorption amount of modification ceramsite is 175.73 mg/g at pH of 5, which is 1.24 times higher than that of the original ceramsite. Coexisting ions in wastewater exhibit minimal interference with Pb
2
⁺ adsorption. In addition, the Pb
2+
adsorption amount remains at 62.11mg/g after three cycles, demonstrating good cyclic stability. The adsorption mechanism analysis shows that the removal of Pb
2+
by modification ceramsite mainly involves ion exchange, electrostatic adsorption, surface complexation and precipitation.