ABSTRACT

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.

摘要

由于自然和人为活动导致的饮用水中过量的 F ^{-是一种严重的健康危害，影响着全世界的人类。}在这项研究中，对八种具有有利 F 吸收结构特性的矿物基材料进行了比较评估^：层状双氢氧化物 (LDH)、地质聚合物、软化球团和鸟粪石。这些材料被认为是低成本的，因为它们要么是废物，要么是副产品，或者可以就地采购。可以得出结论，Ca基材料对F ^-（Ca-Al-CO ₃ LDHs、矿渣基地质聚合物、软化球团）的亲和力最强。_{Ca-Al-CO 3}的朗缪尔吸附容量LDHs、矿渣基地质聚合物和软化球团的含量分别为 20.83、5.23 和 1.20 mg/g。_{发现 Ca-Al-CO 3} LDHs、Mg-Al-Cl LDHs、矿渣基地质聚合物和软化球团对 F ^-的吸收的主要机制是在低初始 F ^-浓度 (<10 mg/L) 时吸附，而沉淀因为建议 CaF _{2在较高的初始 F} ^-浓度 (>20 mg/L)时起主要作用。尽管软化颗粒的 Ca 含量最高（96-97%；XRF），但它们的结构致密，因此 BET 表面积较低（2-3 m ²/g)，导致比基于钙的 LDH 和基于矿渣的地质聚合物更差的性能。然而，地质聚合物以及鸟粪石被认为不适合用于水处理，因为它们由于稳定性差和/或 F^浸出而需要改性。