Stabilization/solidification of hazardous lead glass by geopolymers

Abstract

Stabilization/solidification (S/S) of lead in hazardous waste cathode ray tube (CRT) glass by using geopolymers is a promising disposal method for further construction use. In this study, the effects of fly ash addition and waste CRT glass aggregate on the properties of slag-based geopolymers were investigated. Results show that the addition of 50 wt% fly ash into the geopolymer containing 50 wt% waste CRT glass can mitigate the alkali-silica expansion by 61%, slightly decrease the compressive strength by 1.5 MPa and promote the generation of mullite. On the other hand, the PbO released from waste CRT glass can retard the hydration process, but without changing the crystalline phase composition and the aluminosilicate structure of geopolymers. Therefore, the S/S of waste CRT glass by geopolymers mainly depends on the physical encapsulation effect. Furthermore, fly ash addition can degrade the S/S performance of geopolymers due to the increase of the total porosity representing the channel number. Finally, based on the requirements of volume stability, compressive strength, and leaching concentration of Pb, a mix proportion of 50 wt% fly ash and 50 wt% slag can be proposed for recycling waste CRT glass in a non-hazardous way. Overall, this study is an innovative attempt to reveal the feasibility of utilizing waste CRT glass in geopolymers as fine aggregate.