聚(N-对乙烯基苄基二甲胺)树脂对苯酚的吸附性能

采用二甲胺为功能化试剂,化学修饰氯甲基化苯乙烯-二乙烯基苯共聚物合成了大孔交联聚(N-对乙烯基苄基二甲胺)树脂,测得树脂的氯含量由4.2mmol/g降低到0.24mmol/g,树脂的弱碱交换量为4.0mmol/g,说明氯甲基化苯乙烯-二乙烯基苯共聚物发生胺化反应完全。在水溶液中,测定了大孔交联聚(N-对乙烯基苄基二甲胺)树脂对苯酚的吸附等温线,发现吸附平衡数据符合Freundlich等温吸附方程,相关系数大于0.99。计算得到在吸附量为15、20和25mg/g时,等量吸附焓在-20.81~-30.74kJ/mol范围内,吸附自由能和吸附熵均小于0,说明吸附过程中存在氢键作用,吸附是自发、混乱度变小的过程。比较树脂对水溶液中苯酚、对硝基苯酚和对硝基甲苯的吸附性能以及树脂对水、环己烷、乙醇和乙酸乙酯溶液中苯酚的吸附性能,进一步说明大孔交联聚(N-对乙烯基苄基二甲胺)树脂对水溶液中苯酚的吸附是基于疏水作用和氢键作用协同的机理。

Adsorption of Phenol to Poly(N-p-vinylbenzyl-dimethylamine) Resin

Macroporous crosslinked poly(N-p-vinylbenzyldimethylamine) resin was synthesized from chloromethylated poly(styrene-co-divinylbenzene) with dimethylamine. The residual chlorine in the title resin was 0.24 mmol/g, and its weak basic exchange capacity was 4.0 mmol/g, indicating that the reaction was performed successfully. Adsorption isotherm of phenol onto the title resin from aqueous solution was measured and described with Freundlich isotherm equation with the correlation coefficients greater than 0.99. Isosteric adsorption enthalpies were determined to be -20.81~-30.74 kJ/mol when the adsorption capacities were 15, 20, and 25 mg/g, implying that hydrogen bonding was one of the driving forces for the adsorption. Gibbs adsorption energies and adsorption entropies were both less than 0, which revealed that the adsorption was a spontaneous process leading to higher order. In addition, adsorption of phenol, p-nitrophenol, and p-nitroto-luene onto the resin from aqueous solution as well as that of phenol onto the resin from aqueous, cyclohexane, ethanol, and ethyl acetate solutions were discussed, and the adsorption mechanism via the cooperation between hydrophobic interaction and hydrogen bonding was confirmed.