title: Microcalorimetric and potentiometric titration studies on the adsorption of copper by P. putida and B. thuringiensis and their composites with minerals.
abstract: In order to have a better understanding of the interactions of heavy metals with bacteria and minerals in soil and associated environments, isothermal titration calorimetry (ITC), potentiometric titration and equilibrium sorption experiments were conducted to investigate the adsorption behavior of Cu(II) by Bacillus thuringiensis, Pseudomonas putida and their composites with minerals. The interaction of montmorillonite with bacteria increased the reactive sites and resulted in greater adsorption for Cu(II) on their composites, while decreased adsorption sites and capacities for Cu(II) were observed on goethite-bacteria composites. A gram-positive bacterium B. thuringiensis played a more important role than a gram-negative bacterium P. putida in determining the properties of the bacteria-minerals interfaces. The enthalpy changes (DeltaH(ads)) from endothermic (6.14 kJ mol(-1)) to slightly exothermic (-0.78 kJ mol(-1)) suggested that Cu(II) is complexed with the anionic oxygen ligands on the surface of bacteria-mineral composites. Large entropies (32.96-58.89 J mol(-1) K(-1)) of Cu(II) adsorption onto bacteria-mineral composites demonstrated the formation of inner-sphere complexes in the presence of bacteria. The thermodynamic data implied that Cu(II) mainly bound to the carboxyl and phosphoryl groups as inner-sphere complexes on bacteria and mineral-bacteria composites.
authors.affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.
authors.forename: Linchuan
authors.initials: L
authors.lastname: Fang
authors.forename: Peng
authors.initials: P
authors.lastname: Cai
authors.forename: Pengxiang
authors.initials: P
authors.lastname: Li
authors.forename: Huayong
authors.initials: H
authors.lastname: Wu
authors.forename: Wei
authors.initials: W
authors.lastname: Liang
authors.forename: Xingmin
authors.initials: X
authors.lastname: Rong
authors.forename: Wenli
authors.initials: W
authors.lastname: Chen
authors.forename: Qiaoyun
authors.initials: Q
authors.lastname: Huang
mesh_terms: D000327:Adsorption; D001413:Bacillus thuringiensis / Q000378:metabolism*; D001546:Bentonite / Q000737:chemistry; D001665:Binding Sites; D001673:Biodegradation, Environmental; D002151:Calorimetry; D003300:Copper / Q000302:isolation & purification*; D008903:Minerals; D011199:Potentiometry; D016958:Pseudomonas putida / Q000378:metabolism*; D013816:Thermodynamics; D017186:Titrimetry / Q000379:methods*
chemical_list: D008903:Minerals; D001546:Bentonite; D003300:Copper