title: Removal of aqueous lead by poorly-crystalline hydroxyapatites.
abstract: The use of a phosphorus amendment in altering Pb to a chemically less mobile phase is a promising strategy based on minimizing ecotoxicological risk and improving time and cost efficiency. This study evaluated crystalline and poorly-crystalline hydroxyapatite sorbents on removal of aqueous Pb in response to reaction time, solution pH, and Pb concentration. Batch experiments were conducted using a commercially-available crystalline hydroxyapatite (HA), and two poorly-crystalline hydroxyapatites synthesized from gypsum waste (CHA) and incinerated ash of poultry waste (MHA). Poorly-crystalline hydroxyapatites had greater capacity for Pb removal from a solution with a wider pH range as compared to a crystalline hydroxyapatite. The maximum sorption capacity of Pb determined by the Langmuir model was 500 mg g(-1) for CHA, 277 mg g(-1) for MHA and 145 mg g(-1) for HA. Removal of aqueous Pb by CHA was not dependent on solution pH, with a 98.8% reduction throughout the solution pH range of 2-9, whereas aqueous Pb removal by HA and MHA was pH-dependent with less removal in the neutral solution pH. Poorly-crystalline hydroxyapatites may provide an effective alternative to existing remediation technologies for Pb-contaminated sites.
authors.affiliation: Department of Civil Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan. yhashim@gifu-u.ac.jp
authors.forename: Yohey
authors.initials: Y
authors.lastname: Hashimoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sato
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry; D060729:Coal Ash; D003460:Crystallization; D004785:Environmental Pollutants / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D006882:Hydroxyapatites / Q000737:chemistry*; D007700:Kinetics; D007854:Lead / Q000032:analysis*; D052638:Particulate Matter / Q000737:chemistry; D012996:Solutions
chemical_list: D060729:Coal Ash; D004785:Environmental Pollutants; D006882:Hydroxyapatites; D052638:Particulate Matter; D012996:Solutions; D007854:Lead; D002244:Carbon