聚乙烯亚胺改性硅藻土在低温条件下对氟离子吸附性能研究

STUDY ON ADSORPTION CAPACITY OF POLYETHYLENEIMINE MODIFIED DIATOMITE FOR FLUORIDE ION AT LOW TEMPERATURE

以聚乙烯亚胺改性硅藻土(MD@PEI)作为吸附剂吸附水中氟离子,研究了不同pH、吸附剂投加量、氟离子初始浓度、温度对氟离子吸附过程的影响。结果表明:pH=2、投加量为0.2 g/L、温度为5℃时吸附效果最好。扫描电子显微镜(SEM)显示聚乙烯亚胺成功负载到硅藻土上,意味着MD@PEI是一种优良的多孔吸附剂,并且能够在较低温度下吸附氟离子。傅里叶红外光谱(FTIR)分析表明,MD@PEI吸附剂上氨基(-NH_(2))官能团在吸附氟离子过程中发挥重要作用。Langmuir等温线证实随着温度升高(5~15℃),吸附容量逐渐下降,平衡吸附量(q_(e))与氟离子初始浓度呈正相关性。吸附动力学符合准二级动力学模型,热力学分析证实吸附是一个自发的放热过程。

In this work,the modified diatomite(MD@PEI)was used as an adsorbent to adsorb fluoride ions in water.The effects of pH,adsorbent dosage,initial concentration of fluoride ion and temperature on adsorption parameters were studied.The results indicated that the adsorption efficiency was best when pH=2,dosage was 0.2 g/L and temperature was 5℃.Scanning electron microscopy(SEM)shows that the polyethyleneimine was successfully loaded onto diatomite,which means that MD@PEI is an excellent porous adsorbent.Fourier transform infrared spectroscopy(FTIR)analysis shows the amino(-NH_(2))functional groups onto MD@PEI adsorbent played an important role in the adsorption of fluorine ions.Langmuir isotherm confirmed that the adsorption capacity decreased gradually with the increase of temperature(5~15℃),and the equilibrium adsorption capacity(q_(e))was positively correlated with the initial concentration of fluoride ions.The adsorption kinetics accorded with the pseudo-second-order kinetic model,and the thermodynamic analysis confirmed that the adsorption was a spontaneous exothermic process.