Zenobi María C, Hein Lidia, Rueda Elsa
Departamento de Química, Universidad Nacional del Sur, Avda. Alem 1253 (B8003GRB), Bahía Blanca, Argentina.
J Colloid Interface Sci. 2005 Apr 15;284(2):447-54. doi: 10.1016/j.jcis.2004.10.017.
1-Hydroxyethane-(1,1-diphosphonic acid) (HEDP) is extensively used in many technical applications. This work, as a first stage, examines the adsorption of aqueous HEDP, Cu(II), and Zn(II) onto boehmite (gamma-AlOOH) as single solutes. These processes can be described by the formation of inner-sphere complexes by the surface complexation model with constant capacitance. Uncomplexed HEDP is adsorbed as a mononuclear complex over the entre pH range. Four mononuclear surface complexes with different protonation levels are required to obtain a good fit of the experimental data for the pH range studied. Cu(II)- and Zn(II)-HEDP complexes at equimolar concentrations are studied at high and low surface density. The results indicate that the presence of HEDP significantly promotes metal adsorption at low pH in defects of surface sites. However, metal adsorption exhibits the same trend in the absence and presence of HEDP when the surface sites are in excess. The constant capacitance model successfully describes the experimental data through a ligand-like adsorption complex at low pH. At high pH, the model predicts separate adsorption of divalent metal and HEDP onto different surface sites as the preferred adsorption form.
1-羟基乙烷-（1,1-二膦酸）（HEDP）在许多技术应用中被广泛使用。作为第一阶段的工作，本文研究了水相中的HEDP、Cu(II)和Zn(II)作为单一溶质在勃姆石（γ-AlOOH）上的吸附情况。这些过程可以通过具有恒定电容的表面络合模型形成内球络合物来描述。在整个pH范围内，未络合的HEDP以单核络合物的形式被吸附。需要四种不同质子化水平的单核表面络合物才能很好地拟合所研究pH范围内的实验数据。研究了等摩尔浓度下高表面密度和低表面密度的Cu(II)-HEDP和Zn(II)-HEDP络合物。结果表明，HEDP的存在显著促进了低pH下表面位点缺陷处的金属吸附。然而，当表面位点过量时，无论有无HEDP，金属吸附都呈现相同的趋势。恒定电容模型通过低pH下类似配体的吸附络合物成功地描述了实验数据。在高pH下，该模型预测二价金属和HEDP分别吸附到不同的表面位点上是首选的吸附形式。
