Mechanistic Study of Pb(II) Removal by TiO₂ and Effect of PO₄

Abstract

As a commercial adsorbent, TiO 2 shows a high adsorption capacity for lead (Pb(II)). However, the molecular structure of Pb(II) adsorption on TiO 2 is still unknown. Meanwhile, as a widely used corrosion inhibitor, phosphate (PO 4 ) is usually added into drinking water, and its influential mechanism on Pb(II) removal by TiO 2 remains unknown. Here, the mechanisms of Pb(II) adsorption on TiO 2 and the effect of PO 4 were systematically investigated using a combination of spectroscopic analyses and surface complexation modeling. The adsorption structure of Pb(II) on TiO 2 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 PO 4 , Pb(II) was removed mainly by adsorption on TiO 2 rather than precipitation. Ternary complexation between Pb(II) and PO 4 on TiO 2 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 TiO 2 and develops a model to predict adsorption behaviors, especially in the presence of PO 4 .

Quantitative Insights into Phosphate-Enhanced Lead Immobilization on Goethite

“…Figure displays the Pb L3-edge XANES spectra of samples with 50–300 μM initial Pb and 200–400 μM initial PO 4 concentrations at pH 5 and pH 7, along with the spectra of synthesized HPM. All samples without PO 4 showed peaks at 13051 and 13092 eV, corresponding to bidentate adsorbed Pb, consistent with previous studies. , HPM exhibited distinct peaks at 13047, 13066, and 13083 eV. In addition to these well-defined peaks associated with bidentate adsorbed or precipitate-Pb, some samples exhibited different peaks.…”

“…The Pb–P distance is 3.55 Å in the typical ternary-complex-enriched sample (50 μM Pb and 400 μM PO 4 at pH 5), in which the ternary complex accounted for 68.0% of Pb adsorbed (Table ) as calculated by the CD-MUSIC model. Co-complexation of Pb and PO 4 on other minerals such as TiO 2 and ferrihydrite and goethite with other anions or organic ligands such as sulfate, carbonate, and humic acids ,, have also been investigated in the previous literature.…”

Cu(II) and Cd(II) capture using novel thermosensitive hydrogel microspheres: adsorption behavior study and mechanism investigation

“…In addition, the plot passed through the origin, revealing that the intraparticle diffusion could be the rate-controlling step. 3…”

“…At present, several heavy metal ion removal technologies are used in water treatment, for example chemical precipitation, redox method, 3 membrane separation, ion exchange 4 and adsorption process. 5 Of these methods, adsorption is the best choice because of its relatively low operational costs, simplicity and minimal production of waste.…”

Pb(II) Uptake from Polluted Irrigation Water Using Anatase TiO2 Nanoadsorbent

“…The crystalline planes of nano-TiO 2 are specified by the Miller indices, which were identified from the pattern rings, which agree with the XRD results ( Figure 1 ). Looking at the images, it can be suggested that the Pb adsorbed on nano-TiO 2 formed a polynanocrystalline structure [ 33 , 34 ]. Figure 3 c and Figure S3c show the crystal lattice planes of nano-TiO 2 , for both samples; a crystal lattice plane (110) with a d-spacing of 0.35 nm was estimated.…”