Papadas Ioannis T, Kosma Chariklia, Deligiannakis Yiannis
Department of Environmental and Natural Resources Management, University of Ioannina, Seferi 2, 30100 Agrinio, Greece.
J Colloid Interface Sci. 2009 Nov 1;339(1):19-30. doi: 10.1016/j.jcis.2009.07.008. Epub 2009 Jul 10.
Cu(2+) binding on gamma-Al(2)O(3) is modulated by common electrolyte ions such as Mg(2+), SO(4)(2-), and PO(4)(3-) in a complex manner: (a) At high concentrations of electrolyte ions, Cu(2+) uptake by gamma-Al(2)O(3) is inhibited. This is partially due to bulk ionic strength effects and, mostly, due to direct competition between Mg(2+) and Cu(2+) ions for the SO(-) surface sites of gamma-Al(2)O(3). (b) At low concentrations of electrolyte ions, Cu(2+) uptake by gamma-Al(2)O(3) can be enhanced. This is due to synergistic coadsorption of Cu(2+) and electrolyte anions, SO(4)(2-) and PO(4)(3-)(.) This results in the formation of ternary surface species (SOH(2)SO(4)Cu)(+), (SOH(2)PO(4)Cu), and (SOH(2)HPO(4)Cu)(+) which enhance Cu(2+) uptake at pH<6. The effect of phosphate ions may be particularly strong resulting in a 100% Cu uptake by the oxide surface. (c) EPR spectroscopy shows that at pH<<pH(PZC), Cu(2+) coordinates to one SO(-) group. Phosphate anions form stronger, binary or ternary, surface species than sulfate anions. At pH>>pH(PZC) Cu(2+) may coordinate to two SO(-) groups. At pH<<pH(PZC) electrolyte ions SO(4)(2-) and PO(4)(3-) are bridging one O-atom from the gamma-Al(2)O(3) surface and one Cu(2+) ion forming ternary [gamma-Al(2)O(3)/elecrolyte/Cu(2+)] species.
铜离子（Cu(2+)）在γ-氧化铝（γ-Al(2)O(3)）上的结合受到常见电解质离子（如镁离子（Mg(2+)）、硫酸根离子（SO(4)(2-)）和磷酸根离子（PO(4)(3-)））的复杂调节：（a）在高浓度电解质离子存在下，γ-氧化铝对铜离子的吸收受到抑制。这部分归因于整体离子强度效应，主要是由于镁离子（Mg(2+)）和铜离子（Cu(2+)）之间对γ-氧化铝表面的硫酸根（SO(-)）位点的直接竞争。（b）在低浓度电解质离子存在下，γ-氧化铝对铜离子的吸收可以增强。这是由于铜离子（Cu(2+)）与电解质阴离子硫酸根离子（SO(4)(2-)）和磷酸根离子（PO(4)(3-)）的协同共吸附。这导致形成三元表面物种（SOH(2)SO(4)Cu）(+)、（SOH(2)PO(4)Cu）和（SOH(2)HPO(4)Cu）(+)，它们在pH<6时增强了铜离子的吸收。磷酸根离子的影响可能特别强烈，导致氧化物表面对铜的吸收达到100%。（c）电子顺磁共振光谱（EPR）表明，在pH远低于零电荷点（pH(PZC)）时，铜离子（Cu(2+)）与一个硫酸根（SO(-)）基团配位。磷酸根阴离子形成比硫酸根阴离子更强的二元或三元表面物种。在pH远高于零电荷点（pH(PZC)）时，铜离子（Cu(2+)）可能与两个硫酸根（SO(-)）基团配位。在pH远低于零电荷点（pH(PZC)）时，电解质离子硫酸根离子（SO(4)(2-)）和磷酸根离子（PO(4)(3-)）桥接γ-氧化铝表面的一个氧原子和一个铜离子（Cu(2+)），形成三元[γ-氧化铝/电解质/铜离子（Cu(2+)）]物种。
