title: [Cation exchanges during the process of Cd(2+) absorption by Alfalfa in aqueous solutions].
abstract: A hydroponic experiment was conducted to investigate the cation exchanges during the process of Cd2+ absorption by Alfalfa in aqueous solution. The absorption efficiency of Alfalfa plants with 0-10 mg x L(-1) Cd2+ treatments, changes of Na+, K+, Mg2+, Ca2+ and NH4(+) concentration, and the variation of pH values at different absorption time (0, 1, 2, 4, 8, 12, 24 and 72 h) were studied separately. The multiple linear regressions between Cd2+ absorption and cation variation were analyzed. The results indicated that when Cd2+ concentrations were 0.1, 1, 5, 10 mg x L(-1), the absorption efficiencies of Cd2+ by Alfalfa after 72 h were 85.86%, 52.14%, 15.97% and 7.81%. Cation exchange was involved in the removal of Cd2+ by Alfalfa in aqueous solution. Except for NH4(+), the concentrations of cationic metals Na+, K+, Mg2+ and Ca2+ in aqueous solution increased over time, which increased 11.30% - 61.72%, 21.44% - 98.73%, 24.09% - 8.90% and 37.04% - 191.96%, respectively. Kinetic studies illuminated that the release of Na+, K+, Mg2+ and Ca2+ by Alfalfa in Cd2+ solution with initial concentrations of 0, 0. 1, 1, 5, 10 mg x L(-1) best fitted pseudo-second-order equation,while the NH4(+) release fitted this model when Cd2+ concentrations were 1, 5, 10 mg x L(-1). The gradual decrease of pH during adsorption of Cd2+ by Alfalfa was observed. As the competition ion of Cd2+, H+ might affect the capacity of Alfalfa root system to absorb Cd2+. The ternary linear equation results demonstrated that the content of Cd2+ absorption by Alfalfa strongly related with the release of Ca2+, Mg2+, Na+. And this exchange mainly occurred among Cd2+ and divalent cations.
authors.affiliation: Department of Environmental Engineering, Jinan University, Guangzhou 510632, China. lyp282008@163.com
authors.forename: Yue-Peng
authors.initials: YP
authors.lastname: Li
authors.forename: Hua
authors.initials: H
authors.lastname: Yin
authors.forename: Jin-Shao
authors.initials: JS
authors.lastname: Ye
authors.forename: Hua
authors.initials: H
authors.lastname: Peng
authors.forename: Hua-Ming
authors.initials: HM
authors.lastname: Qin
authors.forename: Yan
authors.initials: Y
authors.lastname: Long
authors.forename: Bao-Yan
authors.initials: BY
authors.lastname: He
authors.forename: Na
authors.initials: N
authors.lastname: Zhang
authors.forename: Yao
authors.initials: Y
authors.lastname: Tong
authors.forename: Su-Fen
authors.initials: SF
authors.lastname: Peng
mesh_terms: D000327:Adsorption; D001673:Biodegradation, Environmental; D002104:Cadmium / Q000302:isolation & purification* / Q000378:metabolism; D002412:Cations / Q000378:metabolism; D000455:Medicago sativa / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism; D012996:Solutions; D014874:Water Pollutants, Chemical / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D002412:Cations; D012996:Solutions; D014874:Water Pollutants, Chemical; D002104:Cadmium