TY - JOUR
T1 - Fluoride removal from water by Ca-Al-CO3 layered double hydroxides and simultaneous acidification
AU - Wei, Liangfu
AU - Zietzschmann, Frederik
AU - Rietveld, Luuk C.
AU - van Halem, Doris
PY - 2021/4
Y1 - 2021/4
N2 - Millions of people worldwide are exposed to excessive concentrations of fluoride (F−) from groundwater sources. Ca-Al-CO3 layered double hydroxides (LDHs) have shown promising defluoridation efficiency; however, defluoridation by Ca-Al-CO3 LDHs is highly pH sensitive. This study showed that simultaneous acidification by conventional acids, such as HCl and CO2 substantially increased the performance of Ca-Al-CO3 LDHs for F- removal at environmentally relevant concentrations (e.g., 10 mg/L) to below the WHO guideline value (1.5 mg/L), while, in comparison to other acids (HNO3, H2SO4, H3PO4), the use of HCl and CO2 does not lead to the introduction of potentially harmful or undesired anions. The addition of HCl and CO2 to LDHs suspensions did lead to changes to the LDHs structure. Leaching experiments, supported by PHREEQC modelling and characterization (SEM-EDX, XRD and FTIR), strongly suggest that the main mechanism of F- removal by Ca-Al-CO3 LDHs was F− adsorption or complexation onto/into various rehydrated mixed metal oxides which re-precipitated upon partial LDHs dissolution when acidifying.
AB - Millions of people worldwide are exposed to excessive concentrations of fluoride (F−) from groundwater sources. Ca-Al-CO3 layered double hydroxides (LDHs) have shown promising defluoridation efficiency; however, defluoridation by Ca-Al-CO3 LDHs is highly pH sensitive. This study showed that simultaneous acidification by conventional acids, such as HCl and CO2 substantially increased the performance of Ca-Al-CO3 LDHs for F- removal at environmentally relevant concentrations (e.g., 10 mg/L) to below the WHO guideline value (1.5 mg/L), while, in comparison to other acids (HNO3, H2SO4, H3PO4), the use of HCl and CO2 does not lead to the introduction of potentially harmful or undesired anions. The addition of HCl and CO2 to LDHs suspensions did lead to changes to the LDHs structure. Leaching experiments, supported by PHREEQC modelling and characterization (SEM-EDX, XRD and FTIR), strongly suggest that the main mechanism of F- removal by Ca-Al-CO3 LDHs was F− adsorption or complexation onto/into various rehydrated mixed metal oxides which re-precipitated upon partial LDHs dissolution when acidifying.
KW - Acidification by HCl and CO
KW - Ca-Al-CO LDHs
KW - Drinking water treatment
KW - Fluoride removal
KW - PHREEQC modelling
UR - http://www.scopus.com/inward/record.url?scp=85100906249&partnerID=8YFLogxK
U2 - 10.1016/j.jwpe.2021.101957
DO - 10.1016/j.jwpe.2021.101957
M3 - Article
AN - SCOPUS:85100906249
SN - 2214-7144
VL - 40
SP - 1
EP - 7
JO - Journal of Water Process Engineering
JF - Journal of Water Process Engineering
M1 - 101957
ER -