TY - JOUR
T1 - Surface mole-ratio method to distinguish surface precipitation and adsorption on solid-liquid interface
AU - Wei, Jinshan
AU - Meng, Xiaoguang
AU - Song, Yonghui
AU - Shi, Qiantao
AU - Wen, Xianghua
AU - Korfiatis, George
N1 - Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2020/10/5
Y1 - 2020/10/5
N2 - 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.
AB - 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.
KW - Adsorption
KW - Lead removal
KW - Phosphate
KW - Precipitation
KW - Surface
KW - Surface mole-ratio method
UR - http://www.scopus.com/inward/record.url?scp=85084223647&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85084223647&partnerID=8YFLogxK
U2 - 10.1016/j.jhazmat.2020.122781
DO - 10.1016/j.jhazmat.2020.122781
M3 - Article
C2 - 32388096
AN - SCOPUS:85084223647
SN - 0304-3894
VL - 397
JO - Journal of Hazardous Materials
JF - Journal of Hazardous Materials
M1 - 122781
ER -