TY - JOUR

T1 - Tuning the stability and phosphate sorption of novel MnII/IVFeII/III layered double hydroxides

AU - Lu, Changyong

AU - Qian, Wenjie

AU - Mallet, Martine

AU - Ruby, Christian

AU - Hansen, Hans Chr Bruun

N1 - Publisher Copyright: © 2021 The Author(s)

PY - 2022

Y1 - 2022

N2 - Layered double hydroxides (LDHs) have been intensively studied for phosphate (Pi) removal but suffer from poor stability and low sorption affinity under ambient conditions. In this paper, well crystallized MnIIFeIIFeIII-Cl, MnIIFeIII-CO3 and novel MnIVFeIII-CO3 LDHs were synthesized. The LDHs show fast Pi sorption with 90 % uptake within 20 min, and high Pi sorption capacity of 11 mg P/g at low solution Pi concenrations of 0.1 mg P/L, corresponding to a very high Pi sorption affinity (Kd 1.1 × 105 L/kg). Fast MnII dissolution from the MnIIFeIIFeIII-Cl LDHs and formation of MnFe2O4 at pH 7 were observed in aqueous suspensions of non-oxidized material where up to 70% of total Mn was released within 2 h. However, when interlayer Cl- was exchanged with CO32−, much lower Mn dissolution (5.4%) was observed. Furthermore, after oxidation of MnII to MnIV, the obtained MnIVFeIII-CO3 LDH maintained the layered structure of LDH and the particles were surrounded by birnessite nanorods. The MnIVFeIII-CO3 LDH showed excellent stability but lower Pi sorption capacity. However, a high sorption affinity was maintained which is attributed to more positively charged Fe-centered sorption sites. XPS and ATR-FTIR data together with DFT calculations demonstrated that Pi was mainly sorbed via the formation of mononuclear mono- and bidentate Pi surface complexes on planar LDH particle surfaces.

AB - Layered double hydroxides (LDHs) have been intensively studied for phosphate (Pi) removal but suffer from poor stability and low sorption affinity under ambient conditions. In this paper, well crystallized MnIIFeIIFeIII-Cl, MnIIFeIII-CO3 and novel MnIVFeIII-CO3 LDHs were synthesized. The LDHs show fast Pi sorption with 90 % uptake within 20 min, and high Pi sorption capacity of 11 mg P/g at low solution Pi concenrations of 0.1 mg P/L, corresponding to a very high Pi sorption affinity (Kd 1.1 × 105 L/kg). Fast MnII dissolution from the MnIIFeIIFeIII-Cl LDHs and formation of MnFe2O4 at pH 7 were observed in aqueous suspensions of non-oxidized material where up to 70% of total Mn was released within 2 h. However, when interlayer Cl- was exchanged with CO32−, much lower Mn dissolution (5.4%) was observed. Furthermore, after oxidation of MnII to MnIV, the obtained MnIVFeIII-CO3 LDH maintained the layered structure of LDH and the particles were surrounded by birnessite nanorods. The MnIVFeIII-CO3 LDH showed excellent stability but lower Pi sorption capacity. However, a high sorption affinity was maintained which is attributed to more positively charged Fe-centered sorption sites. XPS and ATR-FTIR data together with DFT calculations demonstrated that Pi was mainly sorbed via the formation of mononuclear mono- and bidentate Pi surface complexes on planar LDH particle surfaces.

KW - DFT

KW - Mn-Fe LDH

KW - Mn oxidation

KW - Phosphate surface complexation

KW - Solubility

U2 - 10.1016/j.cej.2021.132177

DO - 10.1016/j.cej.2021.132177

M3 - Journal article

AN - SCOPUS:85114702400

VL - 429

JO - Chemical Engineering Journal

JF - Chemical Engineering Journal

SN - 1385-8947

M1 - 132177

ER -