title: Binding characteristics of copper and cadmium by cyanobacterium Spirulina platensis.
abstract: Cyanobacteria are promising biosorbent for heavy metals in bioremediation. Although sequestration of metals by cyanobacteria is known, the actual mechanisms and ligands involved are not very well understood. The binding characteristics of Cu(II) and Cd(II) by the cyanobacterium Spirulina platensis were investigated using a combination of chemical modifications, batch adsorption experiments, Fourier transform infrared (FTIR) spectroscopy and X-ray absorption fine structure (XAFS) spectroscopy. A significant increase in Cu(II) and Cd(II) binding was observed in the range of pH 3.5-5.0. Dramatical decrease in adsorption of Cu(II) and Cd(II) was observed after methanol esterification of the nonliving cells demonstrating that carboxyl functional groups play an important role in the binding of metals by S. platensis. The desorption rate of Cu(II) and Cd(II) from S. platensis surface was 72.7-80.7% and 53.7-58.0% by EDTA and NH(4)NO(3), respectively, indicating that ion exchange and complexation are the dominating mechanisms for Cu(II) and Cd(II) adsorption. XAFS analysis provided further evidence on the inner-sphere complexation of Cu by carboxyl ligands and showed that Cu is complexed by two 5-membered chelate rings on S. platensis surface.
authors.affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Linchuan
authors.initials: L
authors.lastname: Fang
authors.forename: Chen
authors.initials: C
authors.lastname: Zhou
authors.forename: Peng
authors.initials: P
authors.lastname: Cai
authors.forename: Wenli
authors.initials: W
authors.lastname: Chen
authors.forename: Xingmin
authors.initials: X
authors.lastname: Rong
authors.forename: Ke
authors.initials: K
authors.lastname: Dai
authors.forename: Wei
authors.initials: W
authors.lastname: Liang
authors.forename: Ji-Dong
authors.initials: JD
authors.lastname: Gu
authors.forename: Qiaoyun
authors.initials: Q
authors.lastname: Huang
mesh_terms: D000327:Adsorption; D002104:Cadmium / Q000302:isolation & purification*; D003300:Copper / Q000302:isolation & purification*; D000458:Cyanobacteria / Q000737:chemistry; D052918:Environmental Restoration and Remediation / Q000379:methods*; D004951:Esterification; D006863:Hydrogen-Ion Concentration; D007474:Ion Exchange; D019216:Metals, Heavy / Q000302:isolation & purification; D053545:Spirulina / Q000737:chemistry*
chemical_list: D019216:Metals, Heavy; D002104:Cadmium; D003300:Copper