高比表面积羟基磷灰石的制备及其在磷酸铁废水除氟中的应用

Preparation of hydroxyapatite with high specific surface and its application in defluoridation of ferric phosphate wastewater

为提高羟基磷灰石(Hydroxyapatite,HAP)对氟离子的吸附效率,采用化学沉淀法,通过优化反应温度、Ca/P摩尔比、陈化时间等合成条件制备高比表面积HAP,通过FTIR、XRD、XPS、SEM和BET等对合成的HAP进行表征,并评价HAP对模拟废水中氟离子的吸附性能。结果表明:HAP的最优制备条件为反应温度20℃、Ca/P摩尔比1.6、陈化时间24 h,所制备的HAP比表面积达108.0 m^(2)/g;HAP对氟离子的吸附为自发和吸热过程,符合Langmuir吸附模型,在303 K下氟离子的最大吸附容量为13.53 mg/g,吸附过程符合准二级反应动力学模型;在酸性条件下,HAP的除氟机理为离子交换。磷酸铁废水HAP吸附除氟实验表明,出水氟离子浓度可连续32 h低于1.0 mg/L,体现了较好的除氟效果。研究结果可为高效除氟吸附剂的制备以及磷酸铁废水深度除氟提供一定的指导。

In order to improve the adsorption efficiency of hydroxyapatite(HAP)for fluoride ion,HAP with high specific surface area was synthesized by chemical precipitation method through optimizing the preparation conditions such as reaction temperature,Ca/P molar ratio and aging time.The obtained HAP was characterized by FTIR,XRD,XPS,SEM and BET,and its adsorption performance of F~-in simulated wastewater was evaluated.The results showed that the optimal preparation parameters of HAP were as follows:the reaction temperature of 20℃,Ca/P molar ratio of 1.6 and aging time of 24 h.The specific surface area of the HAP synthesized under the optimal conditions was up to 108.0 m^(2)/g.The adsorption process of F~-by HAP was a spontaneous and endothermic process and conformed to the Langmuir model.The maximum absorption capacity of F~-by HAP at 303 K was up to 13.53 mg/g and the adsorption process conformed to the pseudo-second-order reaction kinetic model.The fluoride removal by HAP under acidic conditions was mainly through ion exchange.Continuous adsorption experiment of the prepared HAP in processing ferric phosphate wastewater demonstrated that the effluent F~-concentration could be kept less than 1.0 mg/L for 32 h,showing good defluorination efficiency.The research results can provide some guidance for the preparation of high-efficiency fluoride removal adsorbents and the deep fluoride removal of iron phosphate wastewater.