Removal of aqueous lead by poorly-crystalline hydroxyapatites |
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Authors: | Hashimoto Yohey Sato Takeshi |
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Affiliation: | aDepartment of Civil Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan |
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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. |
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Keywords: | Kinetics Sorption isotherm Heavy metal Phosphorus amendment Apatite Immobilization |
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