Iron (Fe)-manganese (Mn) cutans and their matrix soils in Fragiudalf, Ferrudalf (FER), and Hapludult (HAP) soils of subtropical China were compared for their specific surface area (SSA), point-of-zero charge (PZC), adsorption, and oxidation characteristics on heavy-metal elements. They were studied by chemical analysis and equilibrium adsorption/redox. In the cutans, SSA were greater and PZC were less in their corresponding matrices, which was affected by the high clay organic matter and Fe-Mn oxide contents in the cutans. The SSA of the cutans treated with hydroxylamine hydrochloride (HAHC) was markedly less than the corresponding matrix soils. The PZC were 3.13, 3.65, and 3.90 for matrix soils of Fragiudalf, FER, and HAP, and the PZC were 3.26 and 3.42 for the cutans of FER and HAP, respectively. The cutans adsorbed more Pb2+, Cu2+, Cd2+, and Zn2+ than the corresponding matrix soils. The maximums amounts of heavy-metal elements (Pb2+, Cu2+, Cd2+, Zn2+) adsorbed by cutans treated with HAHC decreased in a range from 53% to 100% compared with those adsorbed by Fe-Mn cutans in the three soils. The maximum of Cr3+ oxidized by cutans treated with HAHC decreased by about 87% to 100% compared with the original cutans of these soils. These results indicate that Mn oxides in the tested Fe-Mn cutans are the main sorbents for heavy-metal ions and the main oxidants of Cr3+.
1Key Laboratory of Subtropical Agriculture Resources and Environment, Ministry of Agriculture, Huazhong Agricultural University, 430070, Wuhan, Hubei Province, China. Mr. Liu is corresponding author. E-mail: firstname.lastname@example.org
2Department of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan.
Received November 21, 2008, and in revised form January 26, 2009.
Accepted for publication January 28, 2009.
This study was supported by Grant No. 40071048 from the National Natural Science Foundation of China.