A review on arsenic removal from coal combustion: Advances, challenges and opportunities

Arsenic is extremely toxic and its release has caused great environmental concerns. Coal combustion is considered to be one of the major anthropogenic emission sources. Arsenic removal technology from coal combustion can be divided into three categories: pre-combustion removal, removal during combustion and post-combustion removal. The post-combustion removal is also called removal from flue gas, which includes several technological developments, namely, the removal using existing air pollutant control devices (APCDs), adsorption, traditional oxidation and advanced oxidation based on removal principle. This review summarizes the latest advances of these arsenic removal technologies. The performance, mechanism and characteristics of arsenic removal technologies were overviewed and analyzed. The merits and drawbacks, and the challenges and prospects of each arsenic removal technologies were discussed. It was found that pre-combustion removal, removal during combustion and removal using APCDs can achieve arsenic removal to a degree, but their removal efficiencies are usually low. Injection of adsorbent into the flue gases can achieve higher arsenic removal efficiency. Calcium-based adsorbents were found to be one of the most efficient ones for arsenic removal. Their shortcoming is the high-temperature sintering and deactivation caused by competitive adsorption of acidic gases. Other adsorbents suffer from low activity, small specific surface area, high cost, or/and little recovery. Further development of advanced adsorbents that are anti-sintering, anti-deactivation, large specific surface area, low-cost, separable, and recyclable should be the main focus in future research. Collaborative control of multiple systems such as removal during combustion, removal using APCDs or/and tail adsorption/oxidation is a promising strategy. Advanced oxidation technologies (AOTs) can achieve high arsenic removal efficiency (90–100%), recovery of arsenic resources and potential simultaneous removal of multi-pollutants, possessing good prospect.