Laboratoire des Procédés Industriels de Synthèse, de l'Environnement et des Energies Nouvelles (LAPISEN); Institut National Polytechnique Félix Houphouët-Boigny, Yamoussoukro, Côte d'Ivoire.
Environnements Dynamiques Territoires Montagnes (EDYTEM), Université Savoie Mont Blanc, Chambéry, France.
J Environ Sci Health A Tox Hazard Subst Environ Eng. 2021;56(6):694-704. doi: 10.1080/10934529.2021.1917937. Epub 2021 May 13.
Defluoridation of groundwater was performed in a batch reactor using bivalve shell powder (BSP) as adsorbent. The physicochemical characteristics of BSP, studied by Fourier Transform Infrared, X-ray Diffraction and Inductively Coupled Plasma-Optical Emission Spectrometry after dissolution, have shown that BSP was mainly composed of crystalline CaCO (∼97.8%). The effects of pH, initial fluoride concentration, adsorbent dose and contact time on the adsorption capacity of BSP were investigated. For an initial fluoride concentration of 2.2 mg/L and with 16 g/L of BSP, after 8 hours of treatment, 27.3% were eliminated at pH 7.5 versus 68% at pH 3, highlighting the efficiency of the adsorption process. The difference in adsorption capacity as a function of pH was correlated to the pHpzc of the BSP, which was equal to 8.2. Thus, at pH below pHpzc, electrostatic attraction between the fluoride anions and the positively charged adsorbent could justify the adsorption mechanism. Fittings of experimental data have evidenced that the adsorption kinetics were of pseudo-second order whereas the adsorption isotherms were of Langmuir type. The chemical precipitation of calcium fluoride was also revealed to occur upon release of Ca from partial dissolution of CaCO in acidic conditions.
采用双壳贝类粉末（BSP）作为吸附剂，在间歇式反应器中对地下水进行除氟处理。通过溶解后傅里叶变换红外光谱、X 射线衍射和电感耦合等离子体发射光谱分析，研究了 BSP 的物理化学特性，结果表明 BSP 主要由结晶 CaCO（约 97.8%）组成。考察了 pH 值、初始氟浓度、吸附剂用量和接触时间对 BSP 吸附容量的影响。对于初始氟浓度为 2.2mg/L，BSP 用量为 16g/L 的条件下，在 pH 值为 7.5 时处理 8 小时后，去除率为 27.3%，而在 pH 值为 3 时，去除率为 68%，这突出了吸附过程的效率。pH 值对吸附容量的影响差异与 BSP 的 pHpzc 值有关，BSP 的 pHpzc 值等于 8.2。因此，在 pH 值低于 pHpzc 值时，氟阴离子与带正电荷的吸附剂之间的静电吸引可以解释吸附机制。实验数据的拟合表明，吸附动力学符合准二级动力学，而吸附等温线符合 Langmuir 型。在酸性条件下，CaCO 的部分溶解会释放 Ca，从而导致 CaF2 的化学沉淀。
