亚甲基蓝在柠檬酸酯化改性麦杆上吸附的动力学和热力学行为

Kinetic and thermodynamic behaviors of cationic dye sorption on wheat straw esterified by citric acid

本研究探索了阳离子染料吸附于柠檬酸酯化改性麦杆(EWS)上的动力学和热力学行为,选择了阳离子染料亚甲基蓝(MB)作为吸附剂。采用静态批次实验改变不同实验因素(温度、pH值、吸附剂量、吸着物浓度、吸附时间)来测定染料吸附的动力学和热力学参数。亚甲基蓝在pH≥4时达到最大吸附值,对于浓度为250mg/l的染料溶液,EWS用量≥2.0g/l能几乎完全去除。对于浓度在50-350mg/l的染料溶液,2.0g/l以上的EWS能够去除95%以上的亚甲基蓝。实验数据符合Langmuir吸附等温线模型,准二级动力学方程能描述其吸附过程。粒子内扩散的二重线性表明在染料吸附过程中有两个粒子内扩散步骤,热力学研究表明染料吸附行为是自发且吸热的,高温有利于吸附。

In this study, the kinetic and thermodynamic behaviors of cationic dye sorption from aqueous solution onto citric acid esterifying wheat straw （EWS） were investigated. The cationic dye, methylene blue （MB）, was selected as sorbate. The kinetic and thermodynamic parameters of dye sorption were examined with a batch system by changing various experimental factors （ e. g. nitial pH, EWS dosage, dye concentration, contact time, temperature）. The MB removal ratio came up to the maximum value beyond pH 4. The 2. 0 g,/1 or up of EWS could almost completely remove MB from 250 mg/1 of dye solution. The sorption percentage of MB kept above 95% over a range from 50 to 350 mg,/1 of dye concentration when 2. 0 g/1 of EWS was used. The isothermal data followed the Langmuir model. The sorption process could be described by the pseudo-second- order kinetic model. The dual linear plot of intraparticle diffusion indicated that two intraparticle diffusion steps occurred in the dye sorption process. The thermodynamic study indicated that the sorption of dye was spontaneous and endothermic. High temperatures favored the sorption processes.