Zhong Xiaocong, Chen Chen, Yan Kang, Zhong Shuiping, Wang Ruixiang, Xu Zhifeng
Faculty of Materials Metallurgy and Chemistry, Jiangxi University of Science and Technology, Ganzhou, China.
State Key Laboratory of Separation and Comprehensive Utilization of Rare Metals, Guangzhou, China.
Front Chem. 2022 Mar 4;10:859969. doi: 10.3389/fchem.2022.859969. eCollection 2022.
La-loaded absorbents have been widely reported for fluoride removal due to the strong affinity of La towards fluoride ion. Herein, chemical removal of fluoride from flue gas scrubbing wastewater using lanthanum salt is investigated. The retaining free F concentration, phase composition and morphology of filtration residues, and the distribution of fluorine have been investigated using ion-selective electrode, analytical balance, scanning electron microscopy, and X-ray diffractor. The results show that at La/F molar ratio ≥1:3.05, the majority of fluorine exists as LaF complexes, leading to the failure of fluoride removal. At 1:3.20 ≤ La/F molar ratio ≤1:3.10, the formation of LaF is facilitated. However, co-existing LaF tends to absorb on the surface of LaF particles, leading to the formation of colloidal solution with large numbers of LaF·LaF suspended solids. At an optimized La/F molar ratio of 1:3.10, a fluoride removal of 97.86% is obtained with retaining fluorine concentration of 6.42 mg L. Considering the existing of positively charged LaF and LaF·LaF , coagulation removal of fluoride is proposed and investigated using lanthanum salts and negatively charged SiO·HO colloidal particles, which is provided NaSiO hydrolysis at pH near 5.5. At a La/F molar ratio of 1:3.00 and NaSiO dose of 0.50 g L, a fluoride removal of 99.25% is obtained with retaining fluorine concentration of 2.24 mg L. When NaSiO dose increases to 1.00 g L, the retaining fluorine concentration could be further reduced to 0.80 mg L.
由于镧对氟离子具有很强的亲和力，负载镧的吸附剂已被广泛报道用于去除氟。在此，研究了使用镧盐化学去除烟气洗涤废水中的氟。使用离子选择性电极、分析天平、扫描电子显微镜和X射线衍射仪研究了滤液中氟的残留浓度、过滤残渣的相组成和形态以及氟的分布。结果表明，当镧/氟摩尔比≥1:3.05时，大部分氟以LaF 配合物的形式存在，导致氟去除失败。当1:3.20≤镧/氟摩尔比≤1:3.10时，有利于LaF的形成。然而，共存的LaF 倾向于吸附在LaF颗粒表面，导致形成含有大量LaF·LaF 悬浮固体的胶体溶液。在优化的镧/氟摩尔比为1:3.10时，氟去除率为97.86%，氟残留浓度为6.42mg/L。考虑到带正电的LaF 和LaF·LaF 的存在，提出并研究了使用镧盐和带负电的SiO·HO胶体颗粒进行凝聚除氟，这是通过在pH接近5.5时使NaSiO水解来实现的。在镧/氟摩尔比为1:3.00和NaSiO投加量为0.50g/L时，氟去除率为99.25%，氟残留浓度为2.24mg/L。当NaSiO投加量增加到1.00g/L时，氟残留浓度可进一步降至0.80mg/L。
