Addition of waste glass for improving the immobilization of heavy metals during the use of electroplating sludge in the production of clay bricks

A novel strategy for improving the immobilization of heavy metals during the use of electroplating sludge in the production of clay bricks, was proposed by the addition of waste glass. Waste glass addition reduced open porosity and surface area, and enhanced compressive strength remarkably. With the adding amount of waste glass powder up to 30 wt.%, surface area and open porosity declined from 0.84 to 0.05 m2/g and from 10.69 to 1.16%, respectively. Compressive strength increased from 20 to 32.7 MPa. Moreover, the leaching concentration of heavy metals decreased considerably and met the regulation standard. Heavy metals, Cu and Zn, have been incorporated into stable spinels phase and adding waste glass was favored to the formation of spinel. It was regarded that waste glass and andesine melted and formed liquid phase during firing process, which improved the mass transfer and the reaction kinetic of spinels formation. The liquid phase filled in the pores and densified bricks body, which also play a important role in preventing heavy metals from releasing. Overall results suggested the addition of waste glass powder was a promising method in improving immobilization of heavy metals during the use of electroplating sludge in production of clay bricks.