Reuse of lead glass sludge in the fabrication of thermally insulating foamed glass with outstanding properties and high Pb-stabilization

Hamdy A Abdel-Gawwad,Mohammed A Arif,Hamada Shoukry,Mona S Mohammed

doi:10.1007/s11356-022-19184-0

Abstract

This study represents the sustainable/safe consumption of lead glass sludge (LGS) in the fabrication of thermally insulating foamed glass via sintering (750–950º C) and chlorination processes. The impact of selected additives including calcium chloride (CaCl2) and sodium hydroxide (NaOH) on the foaming efficiency and Pb-stabilization has been deeply investigated. LGS is mainly lead silicate material with considerable content of calcium carbonate, which acts as foaming agent during sintering process. The newly developed foamed-materials exhibited thermal conductivity of 0.054–0.136 W/m.K, density of 0.23–1.10 g/cm3, porosity of 63.3–92.6%, and compressive strength of 0.10–2.69 MPa. X-ray diffraction proved that the immobilization mechanism was attributed to the transformation of free Pb within LGS into insoluble ganomalite Pb9Ca5MnSi9O33 phase. Adding NaOH enhanced the foaming process accompanied by a significant reduction in Pb-leaching. Incorporating CaCl2 has resulted in a retardation in Pb-leaching, which associated with Pb-stabilization and Pb-vaporization. In an attempt to reduce CO2-emission, the potential use of alkali-rich-wastewater (AW) as eco-friendly alkali source in lieu of NaOH was studied. Regardless of the variation in Pb-concentrations in leachates, all samples recorded Pb-concentrations lower than the safe limit (≤ 5 mg/l), achieving Pb-immobilization of 95.98–99.87%. The significantly reduced thermal conductivity and enhanced Pb-immobilization efficiency along with the reasonable compressive strength summarize the major innovation presented in this study.

Highlights

Lead (Pb)-bearing-wastes are categorized as accumulative hazardous pollutants, which cause serious problems to the human health and environment (WHO, 2019)
X-ray diffraction (XRD) shows (Fig. 1) that lead glass sludge (LGS) exhibits amorphous pattern with the appearance of crystalline peaks affiliated to calcium carbonate (CaCO3) and silicon. SiO2 and PbO
As identified by TG-curve, the weight loss affiliated to organic matter equals 10.12%, representing 71% of the total weight loss of LGS

Summary

Introduction

Lead (Pb)-bearing-wastes are categorized as accumulative hazardous pollutants, which cause serious problems to the human health and environment (WHO, 2019). Thermal treatment of Pb-bearing-wastes is one of the most effective methods for stabilization and removal of. Pb. Adding chloride salt before thermal treatment greatly enhanced the removal of Pb via chlorination/evaporation process (Yu et al 2013; Nowak et al 2010; Nowak et al 2012). Calcium chloride, and sodium chloride salts are the main chloride salts used in the chlorination of Pb (Nowak et al 2012). Nowak et al 2010, 2012) found that the chlorination/evaporation of Pb via calcium chloride is more efficient than sodium chloride. Calcium oxide was found to exhibit a retardation effect on PVC-induced Pb-volatilization; whereas it has no effect on the direct chlorination of sodium chloride-containing-system (Wang et al 2017)

Methods

Results

Discussion

Conclusion