阳离子表面活性剂改性四氧化三铁-沸石复合材料对水中刚果红的去除作用

Removal of Congo red from aqueous solution using cationic surfactant-modified magnetite /zeolite composite as adsorbent

制备了四氧化三铁-沸石复合材料(磁性沸石)和阳离子表面活性剂改性磁性沸石(有机改性磁性沸石),采用X射线衍射分析对有机改性磁性沸石进行了表征,通过批量实验考察了有机改性磁性沸石对水中刚果红的吸附性能,并对相关的吸附机制进行了讨论。实验表明,有机改性磁性沸石对水中的刚果红具备良好的吸附能力,且有机改性磁性沸石对刚果红的吸附能力远远高于磁性沸石。有机改性磁性沸石对水中刚果红的吸附动力学符合准二级动力学模型,吸附平衡数据可以采用Langmuir、Freundlich和Dubinin-Radushkevich(D-R)等温吸附模型加以描述。根据Langmuir等温吸附模型计算得到的有机改性磁性沸石对刚果红的最大吸附容量为146 mg/g(pH 7和30℃)。有机改性磁性沸石对水中刚果红的吸附属于自发和放热的过程。有机改性磁性沸石吸附水中刚果红的作用机制包括静电吸引、有机相分配、氢键和表面配位。X射线衍射分析结果表明,有机改性磁性沸石含四氧化三铁,吸附刚果红后的有机改性磁性沸石可以很容易地通过外加磁场的作用快速地从水中分离出来。上述结果表明,有机改性磁性沸石适合作为一种吸附剂去除废水中的刚果红。

Magnetite /zeolite composite( MZC) was synthesized and then cationic surfactant-modified MZC( SMMZC) was prepared by loading of cetylpyridinium bromide( CPB) on MZC. The SMMZC was characterized by X-ray differaction( XRD). The adsorption of Congo red( CR) from aqueous solution on SMMZC as a function of adsorbent dosage,contact time,initial adsorbate concentration,temperature and pH was investigated using batch experiments. SMMZC was effective for the removal of CR from aqueous solution. SMMZC exhibited much higher CR adsorption capacity than MZC. The adsorption kinetics of CR on SMMZC could be described by a pseudo-second-order model. The equilibrium adsorption data of CR on SMMZC could be described by the Langmuir,Freundlich and Dubinin-Radushkevich( D-R) isotherm models. The maximum monolayer adsorption capacity for CR derived from the Langmuir isotherm model was determined to be 146 mg /g at pH 7 and 30℃. Thermodynamic parameters such as Gibbs free energy change,enthalpy change and entropy change were calculated and the results showed that the adsorption of CR on SMMZC was a spontaneous and exothermic process. The main mechanisms for the adsorption of CR on SMMZC include electrostatic attraction,organic partitioning,hydrogen bonding and surface complexation. XRD analysis revealed that SMMZC contained magnetite( Fe3O4). The SMMZC adsorbed with CR could be collected from aqueous solution under an external magnetic field quickly. Results of this study suggest SMMZC to be applicable for the removal of CR from wastewater.