As a commercial adsorbent, TiO₂ shows a high adsorption capacity for lead (Pb(II)). However, the molecular structure of Pb(II) adsorption on TiO₂ is still unknown. Meanwhile, as a widely used corrosion inhibitor, phosphate (PO₄) is usually added into drinking water, and its influential mechanism on Pb(II) removal by TiO₂ remains unknown. Here, the mechanisms of Pb(II) adsorption on TiO₂ and the effect of PO₄ were systematically investigated using a combination of spectroscopic analyses and surface complexation modeling. The adsorption structure of Pb(II) on TiO₂ was revealed as a tridentate mononuclear configuration by the extended X-ray absorption fine structure (EXAFS) analysis. In the presence of 0.1–5 mg/L PO₄, Pb(II) was removed mainly by adsorption on TiO₂ rather than precipitation. Ternary complexation between Pb(II) and PO₄ on TiO₂ surfaces was found based on EXAFS and in situ Fourier transform infrared characterizations. These complexation structures were used to build a surface complexation model to accurately simulate and predict Pb(II) removal under different conditions. This study provides essential information about the mechanisms of Pb(II) removal by TiO₂ and develops a model to predict adsorption behaviors, especially in the presence of PO₄.

中文翻译：

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TiO ₂去除Pb（II）的机理及PO _4的作用

作为市售的吸附剂，TiO ₂对铅（Pb（II））的吸附能力高。但是，仍然不清楚Pb（II）在TiO ₂上的吸附分子结构。同时，作为一种广泛使用的腐蚀抑制剂，磷酸盐（PO ₄）通常被添加到饮用水中，其对TiO ₂去除Pb（II）的影响机制仍然未知。在这里，结合光谱分析和表面络合建模系统地研究了Pb（II）在TiO ₂上的吸附机理和PO ₄的作用。Pb（II）在TiO ₂上的吸附结构通过扩展的X射线吸收精细结构（EXAFS）分析显示出三齿单核构型。在0.1-5 mg / L PO ₄的存在下，Pb（II）的去除主要是通过在TiO ₂上的吸附而不是沉淀。基于EXAFS和原位傅里叶变换红外表征，发现TiO ₂表面Pb（II）和PO ₄之间存在三元络合物。这些络合结构用于建立表面络合模型，以精确模拟和预测在不同条件下的Pb（II）去除。这项研究提供了有关TiO ₂去除Pb（II）机理的基本信息，并开发了一种模型来预测吸附行为，尤其是在存在PO的情况下₄。