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)