State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; National Engineering Laboratory for Industrial Wastewater Treatment, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; National Engineering Laboratory for Industrial Wastewater Treatment, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
J Hazard Mater. 2021 Feb 5;403:124039. doi: 10.1016/j.jhazmat.2020.124039. Epub 2020 Sep 18.
The strongly acidic wastewater containing fluoride [F(-I)] is generally neutralized using lime, producing massive hazardous solid waste, which may present serious environmental risks. In this study, a novel precipitant, N,N'-Bis(3-(triethoxysilyl)propyl)thiourea, was developed for the selective removal of F(-I) from strongly acidic wastewater. The precipitant was synthesized using (3-aminopropyl)triethoxysilane and thiourea at a molar ratio of 2:1 under 160 ℃. More than 90% of initial F(-I) was removed by the prepared precipitant from strong acidic wastewater produced by nonferrous metal smelting industry, and the residual F(-I) concentration decreased to below 100 mg/L. The F(-I) removal performance is almost free from the interference of coexisting ions. Only 6 kg/m of fluoride slag, which can be recycled as a concrete waterproofing agent, was produced. The F(-I) removal mechanism including substitution, polycondensation, ion exchange and complexation was clarified: ‒OH on Si atoms in the hydrolysis product of BTPT was substituted by F(-I), and a fluoro-substituted product formed; the polycondensation of BTPT and fluoro-substituted product produced polymer precipitates; the specific adsorption of F(-I) on the polymer precipitates occurred through ion exchange with ‒OH and complexation with -NH-.
含氟 [F(-I)] 的强酸性废水通常使用石灰中和，会产生大量危险的固体废物，可能带来严重的环境风险。在本研究中，开发了一种新型沉淀剂 N,N'-双(3-(三乙氧基硅基)丙基)硫脲，用于从强酸性废水中选择性去除 F(-I)。沉淀剂是在 160°C 下，将摩尔比为 2:1 的 (3-氨丙基)三乙氧基硅烷和硫脲合成的。从有色金属冶炼行业产生的强酸性废水中，用制备的沉淀剂可去除初始 F(-I) 的 90%以上，残留的 F(-I)浓度降低到 100mg/L 以下。F(-I) 的去除性能几乎不受共存离子的干扰。仅产生 6kg/m 的氟化物渣，可回收用作混凝土防水剂。澄清了包括取代、缩聚、离子交换和络合在内的 F(-I) 去除机制：BTPT 水解产物中的 Si 原子上的 -OH 被 F(-I)取代，形成氟取代产物；BTPT 和氟取代产物的缩聚生成聚合物沉淀；F(-I)通过与 -OH 的离子交换和与 -NH-的络合作用，特异性吸附在聚合物沉淀上。
