Relationship between Pb2+ adsorption and average Mn oxidation state in synthetic birnessites
Zhao, Wei (Huazhong Agricultural University. Key Lab of Subtropical Agriculture Resource and Environment)
Cui, Haojie (Huazhong Agricultural University. Key Lab of Subtropical Agriculture Resource and Environment)
Liu, Fan (Huazhong Agricultural University. Key Lab of Subtropical Agriculture Resource and Environment)
Tan, Wenfeng (Huazhong Agricultural University. Key Lab of Subtropical Agriculture Resource and Environment)
Feng, Xionghan (Huazhong Agricultural University. Key Lab of Subtropical Agriculture Resource and Environment)

Data:	2009
Resum:	The relationship between vacant Mn structural sites in birnessites and heavy-metal adsorption is a current and important research topic. In this study, two series of birnessites with different average oxidation states (AOS) of Mn were synthesized. One birnessite series was prepared in acidic media (49. 6-53. 6 wt. % Mn) and theother in alkaline media (50. 0-56. 2 wt. % Mn). Correlations between the Pb adsorption capacity and the d interlayer spacing, the AOS by titration, and the release of Mn, H, and K during adsorption of Pb were investigated. The maximum Pb adsorption by the birnessites synthesized in acidic media ranged from 1320 to 2457 mmol/kg with AOS values that ranged from 3. 67 to 3. 92. For birnessites synthesized in alkaline media, the maximum Pb adsorption ranged from 524 to 1814 mmol/kg, with AOS values between 3. 49 and 3. 89. Birnessite AOS values and Pb adsorption increased as the Mn content decreased. The maximum Pb adsorption to the synthetic birnessites calculated from a Langmuir fit of the Pb adsorption data was linearly related to AOS. Birnessite AOS was positively correlated to Pb adsorption, but negatively correlated to the d spacing. Vacant Mn structural sites in birnessite increased with AOS and resulted in greater Pb adsorption. Birnessite AOS values apparently reflect the quantity of vacant sites which largely account for Pb adsorption. Therefore, the Pb adsorption capacity of birnessite is mostly determined by the Mn site vacancies, from which Mn, H, and K released during adsorption were derived.
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Adsorption ; Birnessite ; Mn Average Oxidation State ; Pb2+ ; Vacant Mn Structural Site
Publicat a:	Clays and Clay Minerals, Vol. 57, Núm. 5 (2009) , p. 513-520, ISSN 1552-8367

DOI: 10.1346/CCMN.2009.0570501

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