聚乙烯亚胺表面改性硅藻土及其对苯酚吸附特性的研究

使用紫外吸收光度法研究了硅藻土对聚乙烯亚胺(PEI)的等温吸附;采用浸渍法,用PEI对硅藻土进行了表面改性;使用4-氨基安替比林光度法研究了经PEI表面改性的硅藻土对苯酚的捕集行为.研究结果表明,凭借强烈的静电相互作用,表面带负电荷的硅藻土粉体对阳离子性大分子PEI具有很强的吸附能力,等温吸附满足Freundlich吸附方程;经PEI表面改性后,硅藻土粉体表面的电性发生了根本性改变,且等电点由pH=2.0移至pH=10.5;在中性溶液中,改性粉体通过氢键作用与静电相互作用的协同,对水溶液中的苯酚会产生很强的捕集作用,饱和吸附量可达92 mg/g;在酸性溶液中改性粉体通过氢键相互作用,对水溶液中的苯酚产生一定的吸附作用,但由于PEI分子链高度的质子化,氮原子对苯酚的氢键相互作用很弱,吸附量很低.

STUDIES ON THE ADSORPTION BEHAVIOR OF POLYETHYLENEIMINE-MODIFIED DIATOMITE TOWARDS PHENOL

The adsorption isotherm of polyethyleneimine(PEI) modified diatomite was studied using UV spectrophotometry.The surface of diatomite was modified with polyethyleneimine by using impregnation method,and the trapping behavior of the modified diatomite for phenol was investigated by using 4-aminoantipyrine method.The experiment results showed that negatively charged diatomite particles had very strong adsorption effect for cationic macromolecules of PEI,and it was attributed to the strong electrostatic interaction.The adsorption isotherm fits the Freundlich equation.After modification,the electric properties on the surface of diatomite particles changed factually,and the isoelectric point moved from pH=2.0 to pH=10.5. In acidic solutions,phenol exists as molecules,and the modified particles adsorb phenol through hydrogen bonding interaction.However the hydrogen bonding interaction between nitrogen atoms on PEI chains and phenol is weak because of the high degree of protonation of polyethyleneimine macromolecules,so the adsorption quantity is low.In basic solutions,phenol exists as phenoxy anions,and the modified particles adsorb phenol through electrostatic interaction.However the electrostatic interaction between PEI and phenoxy anions is very weak owing to the low degree of protonation of polyethyleneimine macromolecules,so the adsorption quantity is much lower.The modified particles exhibit very strong trapping effect for phenol through the cooperation of strong electrostatic interaction with hydrogen bond effect in neutral solutions,and the saturated adsorption capacity can be as high as 92 mg/g.