硅烷化赤泥的制备及其对水中铅离子吸附性能分析

PREPARATION OF SILANIZED RED MUD AND ITS ADSORPTION PROPERTIES FOR LEAD IONS IN WATER

采用浓盐酸、3-氨丙基三乙氧基硅烷(APTES)依次对赤泥进行处理、改性,制备出1种去除率高、吸附量大、吸附效果好的重金属离子吸附剂。通过SEM、XRD、BET、元素分析、FTIR、热重分析等手段对其进行表征,并探究溶液pH、吸附剂投加量以及吸附温度等条件对水溶液中Pb 2+吸附效果的影响。结果表明:经浓盐酸酸浸和有机改性后,拜耳法赤泥比表面积显著增大且氨基成功嫁接到赤泥表面。硅烷化赤泥对铅的吸附时间在80 min达到平衡,其最佳吸附pH为6,最佳吸附剂投加量为2 g/L,对应的饱和吸附量为361 mg/g。吸附过程符合准二级动力学模型和Freundlich吸附等温模型,热力学数据说明该吸附是吸热、自发的过程。同时经XPS光谱分析证实,吸附机理主要是硅烷化赤泥表面嫁接氨基,氨基上的氮原子存在孤对电子,可通过与Pb 2+的螯合作用而有效去除Pb 2+。

Red mud was treated and modified by concentrated hydrochloric acid and 3-aminopropyltriethoxysilane(APTES)in this paper,thus a heavy metal ion adsorbent with high removal rate,large adsorption capacity and good adsorption effect was prepared.Then it was characterized by SEM,XRD,BET,elemental analysis,FTIR and thermogravimetric analysis.The effects of solution pH,adsorbent dosage and adsorption temperature on the adsorption of Pb 2+by the adsorbent in aqueous solution were investigated.The results showed that the specific surface area of red mud was significantly increased by acid hydrochloric acid leaching and organic modification,and the amino group was successfully grafted onto the surface of red mud.The adsorption lead by silylation modified red mud reached equilibrium at 80 min,the optimum adsorption pH was 6,the optimum adsorbent dosage was 2 g/L,and the saturated adsorption amount was 361 mg/g.The adsorption process was in good agreement with the quasi-secondary kinetic model and the Freundlich adsorption isotherm model.The thermodynamic data indicated that the adsorption was an endothermic and spontaneous process.At the same time,XPS spectroscopy confirmed that the adsorption mechanism was mainly grafting amino groups on surface of the silanized red mud.The nitrogen atoms on the amino groups had lone paired electrons,which could effectively remove Pb 2+through chelation.