茶渣负载纳米四氧化三铁复合材料制备及其对亚甲基蓝的吸附机理

Preparation of tea waste-nano Fe_3O_4 composite and its removal mechanism of methylene blue from aqueous solution

采用化学沉淀法将Fe_3O_4纳米颗粒负载到茶渣(tea waste,TW)上,之后对TW-Fe_3O_4复合材料进行表征,并研究其对典型染料废水亚甲基蓝(MB)的去除效果及机理.结果表明,固液比为4.0 g·L^(-1),p H(6.92)未调整,接触时间为120 min,TW-Fe_3O_4对亚甲基蓝去除率可达98.70%.拟二级动力学模型可较好描述TW-Fe_3O_4吸附亚甲基蓝的过程.TW-Fe_3O_4复合材料对亚甲基蓝的去除可分为快吸附和慢吸附两个阶段.Langmuir、Temkin和Dubinin-Radushkevich模型均能较好拟合吸附过程.Langmuir拟合得到的最大饱和吸附量为84.47 mg·g^(-1).3次吸附-解吸循环实验之后,发现TW-Fe_3O_4对MB去除效果有限,表明结合较为稳定.TW-Fe_3O_4对MB的吸附机理涉及静电作用、离子交换、氢键作用、π-π堆积等.动力学、FTIR和XPS分析显示茶渣的表面官能团在吸附中能发挥重要作用.因此,TW-Fe_3O_4复合材料有作为染料污染废水修复剂的潜力,且能较为方便的从溶液中分离.

Nano Fe3 O4 was loaded onto tea waste to prepare TW-Fe3 O4 composite using chemical precipitation method. The composite was characterized by BET, SEM, TEM, XRD, FTIR, XPS, ICP, VSM, and was applied to investigate the removal effect and mechanism of methylene blue solution. The results indicated that the removal rate reached 98.70％ when the dosage 4.0 g·L-1 , the pH of MB solution was 6.92 and contact time was 2 h. The pseudo-second-order kinetic model well described the adsorption process of methylene blue into TW-Fe3 O4 composite. The adsorption process could be divided into two stages： fast adsorption stage and slow adsorption stage. Langmuir, Temkin, Dubinin-Radushkevich well fit the adsorption isotherm process. The adsorption capacity of MB was 84.47 mg·g-1 based on Langmuir fitting. After three cycles of adsorption and desorption process, the removal effect of TW-Fe3 O4 composite was limited, suggesting the adsorption was stable and the process would not cause secondary pollution. The mechanism between TW-Fe3 O4 and MB involved ion exchange, hydrogen bonding, π-π interaction, electrostatic interaction, etc. Surface functional groups of TW-Fe3 O4 composite played an important role during the adsorption process based on kinetics, FTIR, XPS analysis. Therefore, TW-Fe3 O4 composite possesses the potential to act as an adsorbent to remove dyeing wastewater and could be easily separated from the aqueous solution.