Journal of Hazardous Materials 403 (2021) 124017 Available online 18 September 2020 0304-3894/© 2020 Elsevier B.V. All rights reserved. Stabilization of hazardous lead glass sludge using reactive magnesia via the fabrication of lightweight building bricks Hamdy A. Abdel-Gawwad a, * , S. Abd El-Aleem b , Aya Zayed b a Raw Building Materials and Processing Technology Research Institute, Housing and Building National Research Center (HBRC), Cairo, Egypt b Chemistry Department, Faculty of Science, Fayoum University, Fayoum, Egypt A R T I C L E INFO Keywords: Lead immobilization Lightweight building bricks Magnesium silicate hydrate Hydrocerussite Hydromagnesite ABSTRACT This study focused on the stabilization of lead glass sludge (LGS) using reactive magnesia (MgO) via the fabri- cation of lightweight building bricks. Two types of MgO with different reactivities were prepared by the thermal treatment of magnesium carbonate at 800 ◦ C and 1200 ◦ C (MgO-800 and MgO-1200, respectively). The fabri- cation of bricks and Pb stabilization were performed by wet mixing LGS with MgO followed by humidity in- cubation. Results showed that the Pb immobilization and performance of the produced bricks were strongly affected by MgO reactivity, curing time, and LGS–MgO weight ratios. Pb immobilization was performed by the transformation of soluble lead into an insoluble hydrocerussite phase, particularly in hydrated mixtures with high MgO content (> 25 wt%). Pb immobilization inside a magnesium silicate hydrate skeleton is the main mechanism in the hydrated samples containing 25 wt% MgO. To achieve “sustainability,” we recommend the use of a hydrated mixture containing 75 wt% of LGS and 25 wt% of MgO-800 in the production of building bricks because this mixture exhibits high compressive strength, high Pb immobilization, low energy demand, and low environmental pollution. 1. Introduction Lead-rich materials are a global concern owing to their serious effects on the environment and public health (WHO, 2019). Therefore, the remediation and transformation of hazardous Pb-rich wastes into safe and inert materials is one the biggest challenges in the world. Pb is mainly present in incinerated municipal solid waste or wastes produced from industrial activities, such as the manufacturing of Pb glass, pig- ments, paint, and ceramic glaze (Sato et al., 2020; ElKersh and Haggar, 2015; Avci et al., 2017). The solidifcation/stabilization of Pb-rich ma- terials is one of the preferred solutions for overcoming the hazardous effects of this heavy metal on the environment and human health. Although portland cement exhibits high effciency in the stabilization of Pb, it is not suffciently safe because the binding capacity of hardened cement is greatly reduced in the long run, which results in the release of considerable amounts of Pb into the surrounding environment (Shen et al., 2018, 2019; Zhan et al., 2020). The alkali-activation process is regarded an eco-effcient method in the remediation of heavy metals (Muhammad et al., 2018; Wan et al., 2018). Alkali-activated materials were prepared by mixing an alkaline solution (e.g., sodium hydroxide, sodium silicate, potassium hydroxide, potassium silicate, and sodium sulfate) with aluminosilicate materials (e.g., fy ash, blast-furnace slag, and metakaolin), and this approach resulted in the formation of alkali-activated materials with high engi- neering properties (Pan et al., 2018; Abdel-Gawwad et al., 2020a). Pb immobilization mainly depends on the chemical composition and physical nature of aluminosilicate materials (Nikoliˇ c et al., 2018), Al/Si ratio (Lee et al., 2016), and type of alkali activator (Zheng et al., 2016; Muhammad et al., 2018). Pb immobilization via the alkali-activation process was performed using three different mechanisms, namely, the neutralization of the negative charge localized on tetrahedral alumina within an aluminosilicate network; the formation of a covalent bond between Pb and aluminosilicate; and/or the formation of Pb hydroxide, carbonate, silicate, and aluminate (El-Eswed et al., 2017). In the last decade, the stabilization of Pb-contaminated materials using reactive magnesia (MgO) has received considerable interest owing to its high effciency in Pb immobilization in a short period of time (Shen et al., 2019). The simulated accelerated aging tests confrmed that Pb immobilized by this method showed high long-term stability (~ 52 years) (Shen et al., 2018). Compared with Portland cement, the use of * Corresponding author: Raw Building Materials and Processing Technology Research Institute, Housing and Building National Research Center (HBRC), Cairo, Egypt. E-mail address: hamdyabdelgawwad@yahoo.com (H.A. Abdel-Gawwad). Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat https://doi.org/10.1016/j.jhazmat.2020.124017 Received 13 June 2020; Received in revised form 7 September 2020; Accepted 13 September 2020