# Coal Gangue Recycling in Construction Materials: Strategies for Environmental Risk Mitigation via Heavy Metal Immobilization and Resource Utilization

## TL;DR

This paper reviews strategies to recycle coal gangue in construction materials to reduce environmental risks and heavy metal pollution.

## Contribution

The paper introduces a novel approach for transitioning from heavy metal solidification to active utilization in coal gangue recycling.

## Key findings

- Recycling coal gangue in building materials reduces stockpiling and mitigates heavy metal leaching.
- Heavy metals like Cr, Cu, and Pb in coal gangue can be immobilized through solidification and adsorption mechanisms.
- Over five billion tons of coal gangue remain in China, with heavy metal pollution still a major concern.

## Abstract

Coal gangue represents the predominant solid waste in the coal industry and poses significant risks to both the ecological environment and human health. It has been demonstrated that recycling it in building materials effectively reduces stockpiling, mitigates environmental harm, and minimizes heavy metal leaching. However, a comprehensive review systematically focusing on the recycling of coal gangue and the behavior of its associated heavy metals in building materials is still lacking. This work introduces the physicochemical properties and environmental hazards of coal gangue, including spontaneous combustion, land occupation, and pollution risks. It also summarizes the leaching patterns, speciation, and immobilization mechanisms of heavy metals such as Cr, Cu, and Pb in gangue-based building materials, and reviews adsorption behaviors, solidification pathways, and microstructural interactions at the molecular scale. Despite ongoing efforts, over five billion tons of coal gangue remain accumulated in China, with secondary pollution from heavy metals continuing to pose serious concerns. To address these challenges, recommendations are proposed for establishing standardized leaching evaluation methods, and a novel approach for transitioning from heavy metal solidification to active utilization is introduced. This review aims to provide strategic direction for the green and sustainable recycling of coal gangue.