title: The role of ammonia on mercury leaching from coal fly ash.
abstract: The Federal Clean Air Interstate Rule issued in March 2005 will result in many power plants employing ammonia-based technologies to control NO(x) emission. The Clean Air Mercury Rule, issued at the same time, will encourage many power plants to use various technologies to remove mercury from flue gas, generating fly ashes that contain elevated concentrations of mercury. Ammonia forms relatively strong complexes with mercury compared to most other cationic elements and, therefore, may change the leaching characteristics of mercury. Understanding the impact of ammonia on the leaching of mercury from fly ash is critical in predicting the potential environmental impact of future fly ash. Batch methods were used to investigate the ammonia impact on mercury leaching from fly ash under different pH conditions. The results indicated that mercury leaching without external ammonia addition is not significant. However, ammonia addition increased mercury leaching in the alkaline pH range, due to the formation of less adsorbable mercury-ammonia complexes. Washed ash released more mercury than the raw ash if the ammonia concentration is the same, mainly due to the dissolution of some ash components during washing which exposed more mercury on ash surface. Mercury adsorption data indicated that more than 90% of available mercury was adsorbed by fly ash even in the presence of 1000 mg l(-1) ammonia addition.
authors.affiliation: Department of Civil, Architectural and Environmental Engineering, University of Missouri-Rolla, Rolla, MO 65409, USA. wangjia@umr.edu
authors.forename: Jianmin
authors.initials: J
authors.lastname: Wang
authors.forename: Tian
authors.initials: T
authors.lastname: Wang
authors.forename: Harmanjit
authors.initials: H
authors.lastname: Mallhi
authors.forename: Yu
authors.initials: Y
authors.lastname: Liu
authors.forename: Heng
authors.initials: H
authors.lastname: Ban
authors.forename: Ken
authors.initials: K
authors.lastname: Ladwig
mesh_terms: D000327:Adsorption; D000388:Air / Q000032:analysis* / Q000592:standards; D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry; D000641:Ammonia / Q000032:analysis* / Q000737:chemistry; D002244:Carbon / Q000737:chemistry*; D060729:Coal Ash; D006863:Hydrogen-Ion Concentration; D008628:Mercury / Q000032:analysis* / Q000737:chemistry; D008956:Models, Chemical; D052638:Particulate Matter / Q000737:chemistry*
chemical_list: D000393:Air Pollutants; D060729:Coal Ash; D052638:Particulate Matter; D002244:Carbon; D000641:Ammonia; D008628:Mercury