Surface mole-ratio method to distinguish surface precipitation and adsorption on solid-liquid interface

Jinshan Wei, Xiaoguang Meng, Yonghui Song, Qiantao Shi, Xianghua Wen, George Korfiatis

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

The enhancement effects of phosphate (P) on Pb removal by adsorbents have been attributed to co-adsorption of P and Pb, the formation of P-Pb surface ternary surface complexes, and surface precipitation of P and Pb. However, distinguishing adsorption from surface precipitation in multi-adsorbate systems has been a challenge. For the first time, a surface mole-ratio (SMR) method was established and applied for delineating Pb-P precipitation and Pb adsorption on an acrylic amine fiber (AAF) adsorbent. In elaborating the SMR method, we developed Pb removal experiments by mixing solutions containing 0.2 g/L of AAF, 6 and 12 μmol/L P, and 0–35 μmol/L Pb. When the removed Pb/P (μmol/μmol) was plotted as a function of the equilibrium Pb (μmol/L), the SMR diagram exhibited a turning-point similar to the Pb/P mole ratio of 5/3 = 1.67 in pyromorphite (Pb5(PO4)3OH) precipitate. The SMR diagram indicated that when the Pb concentration increased, the precipitate formed first; after all P formed precipitates, Pb was removed by adsorption. The precipitation and adsorption processes were further confirmed by other SMR diagrams, FTIR, SEM-EDX, and XRD analysis. The SMR method will have broad applications in determining the removal mechanisms of multi-adsorbates by adsorbents and coagulants, and stabilization mechanisms of heavy metals in soils. With the development and application of more modern in-situ characterization techniques, SMR method will be more effective.

Original languageEnglish
Article number122781
JournalJournal of Hazardous Materials
Volume397
DOIs
StatePublished - 5 Oct 2020

Keywords

  • Adsorption
  • Lead removal
  • Phosphate
  • Precipitation
  • Surface
  • Surface mole-ratio method

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