TY - JOUR
T1 - Comparative study of low-cost fluoride removal by layered double hydroxides, geopolymers, softening pellets and struvite
AU - Wei, Liangfu
AU - Li, Zhenming
AU - Ye, Guang
AU - Rietveld, Luuk C.
AU - van Halem, Doris
PY - 2021
Y1 - 2021
N2 - Excessive F- in drinking water due to natural and anthropogenic activities is a serious health hazard affecting humans worldwide. In this study, a comparative assessment was made of eight mineral-based materials with advantageous structural properties for F- uptake: layered-double-hydroxides (LDHs), geopolymers, softening pellets and struvite. These materials are considered low-cost, for being either a waste or by-product, or can be locally-sourced. It can be concluded that Ca-based materials showed the strongest affinity for F- (Ca-Al-CO3 LDHs, slag-based geopolymer, softening pellets). The Langmuir adsorption capacity of Ca-Al-CO3 LDHs, slag-based geopolymer and softening pellets was observed to be 20.83, 5.23 and 1.20 mg/g, respectively. The main mechanism of F- uptake on Ca-Al-CO3 LDHs, Mg-Al-Cl LDHs, slag-based geopolymers and softening pellets was found to be sorption at low initial F- concentrations (<10 mg/L) whereas precipitation as CaF2 is proposed to play a major role at higher initial F- concentrations (>20 mg/L). Although the softening pellets had the highest Ca-content (96-97%; XRF), their dense structure and consequent low BET surface area (2–3 m2/g), resulted in poorer performance than the Ca-based LDHs and slag-based geopolymers. Nevertheless, geopolymers, as well as struvite, were not considered to be of interest for application in water treatment, as they would need modification due to their poor stability and/or F- leaching.
AB - Excessive F- in drinking water due to natural and anthropogenic activities is a serious health hazard affecting humans worldwide. In this study, a comparative assessment was made of eight mineral-based materials with advantageous structural properties for F- uptake: layered-double-hydroxides (LDHs), geopolymers, softening pellets and struvite. These materials are considered low-cost, for being either a waste or by-product, or can be locally-sourced. It can be concluded that Ca-based materials showed the strongest affinity for F- (Ca-Al-CO3 LDHs, slag-based geopolymer, softening pellets). The Langmuir adsorption capacity of Ca-Al-CO3 LDHs, slag-based geopolymer and softening pellets was observed to be 20.83, 5.23 and 1.20 mg/g, respectively. The main mechanism of F- uptake on Ca-Al-CO3 LDHs, Mg-Al-Cl LDHs, slag-based geopolymers and softening pellets was found to be sorption at low initial F- concentrations (<10 mg/L) whereas precipitation as CaF2 is proposed to play a major role at higher initial F- concentrations (>20 mg/L). Although the softening pellets had the highest Ca-content (96-97%; XRF), their dense structure and consequent low BET surface area (2–3 m2/g), resulted in poorer performance than the Ca-based LDHs and slag-based geopolymers. Nevertheless, geopolymers, as well as struvite, were not considered to be of interest for application in water treatment, as they would need modification due to their poor stability and/or F- leaching.
KW - Fluoride
KW - geopolymers
KW - LDHs
KW - softening pellets
KW - struvite
UR - http://www.scopus.com/inward/record.url?scp=85109324937&partnerID=8YFLogxK
U2 - 10.1080/09593330.2021.1946600
DO - 10.1080/09593330.2021.1946600
M3 - Article
C2 - 34157955
AN - SCOPUS:85109324937
SN - 0959-3330
VL - 43 (2022)
SP - 4306
EP - 4314
JO - Environmental Technology (United Kingdom)
JF - Environmental Technology (United Kingdom)
IS - 27
ER -