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近年来,工业化的迅速发展造成了许多环境污染问题。染料废水作为一种典型的工业废水因其水量大、色度高、组成成分复杂而导致其处理难度非常高[1]。若未经处理而排放到自然水体,将会污染水源,威胁生态环境,并且其生物毒性通过食物链而最终在人体积累,严重危害人体健康[2]。目前,染料废水的去除方法主要有物理法、化学法及生物法[3-4]。物理法是目前研究染料废水处理最为广泛的一种处理方法,其中吸附法作为一种绿色高效的去除技术被广泛地应用于染料废水的去除。吸附剂的选择对于使用吸附法去除染料废水至关重要。目前,常用的吸附材料有活性炭、焦炭、沸石、壳聚糖以及天然黏土矿物等[5]。但是这些吸附剂的吸附容量不高,或者选择吸附性差。因此,开发一种高效和大吸附量的吸附剂用于染料废水的去除非常必要。
金属有机骨架是通过共价键或者离子共价键自组装金属中心离子和有机配体形成的具有周期性网络结构的配位聚合物[6]。因其高的比表面积和可调的孔径[7]、丰富的结构和组成成分、配位不饱和位点能够结合特定官能团[8]等特点而被广泛应用于储能、气液相分离、催化、光学和磁学等领域[9-11]。沸石咪唑基骨架(ZIFs)作为MOFs材料的一种,具有优异的化学稳定性和吸附性能。张琪颖[12]研究了ZIF-8对硝基苯酚(PNP)的吸附效果,研究表明,ZIF-8在反应最佳条件下能够高效选择性地吸附PNP。同时,磁性纳米复合材料作为吸附剂应用于水处理中也受到广泛关注。孙杨等[13]利用自制Fe3O4磁性材料与MOF-5合成磁性Fe3O4@MOF-5复合材料,被证明Fe3O4@MOF-5复合材料对于刚果红是良好的吸附剂。基于上述研究,本研究采用聚苯乙烯磺酸钠(PSS)处理Fe3O4表面诱导生长ZIF-8壳层,在常温搅拌下,成功合成磁性核壳金属有机骨架Fe3O4@ZIF-8,通过SEM、TEM、XRD、FT-IR及VSM对其进行形貌分析,考察了刚果红初始浓度及接触时间、Fe3O4@ZIF-8用量、pH等因素对Fe3O4@ZIF-8吸附偶氮染料刚果红废水的影响;确定了其吸附动力学和吸附等温线;探讨了Fe3O4@ZIF-8的选择吸附性能以及循环再生性能,研究可为复合金属有机骨架材料在染料吸附去除方面的应用提供参考。
磁性金属有机骨架Fe3O4@ZIF-8的制备及对偶氮染料刚果红的高效吸附
Preparation of magnetic metal organic framework Fe3O4@ZIF-8 and its high efficient adsorption towards azo dye congo red
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摘要: 采用常温搅拌法,在聚苯乙烯磺酸钠(PSS)处理过的Fe3O4表面诱导生长ZIF-8壳层,成功合成了磁性核壳金属有机骨架Fe3O4@ZIF-8,并对其吸附去除偶氮染料刚果红的性能进行了探究,考察了刚果红初始浓度和接触时间、Fe3O4@ZIF-8投加量以及pH对刚果红去除的影响。SEM、TEM、XRD、FT-IR及VSM表征结果证明,ZIF-8纳米颗粒已成功负载于Fe3O4表面,形成了典型的核壳结构,并且具有优异的磁学性能。吸附实验结果表明,反应最佳pH为6,吸附剂投加量为500 mg·L−1;当反应时间达到180 min 时,吸附达到平衡。吸附反应的吸附动力学和吸附等温线分析表明,刚果红染料在Fe3O4@ZIF-8上的吸附动力学符合二级动力学方程,吸附等温线符合Langmuir模型。Fe3O4@ZIF-8吸附剂对刚果红具有高效的选择吸附性能并且在循环吸附中展现出良好的循环吸附性能。因此,磁性核壳金属有机骨架Fe3O4@ZIF-8作为吸附剂在去除刚果红染料方面有着广阔的应用前景。
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关键词:
- 磁性金属有机骨架 /
- Fe3O4@ZIF-8 /
- 刚果红 /
- 吸附动力学
Abstract: The magnetic core-shell metal organic framework Fe3O4@ZIF-8 was successfully synthesized by treating the surface of Fe3O4 with sodium polystyrene sulfonate (PSS) and inducing ZIF-8 shell growth on it under continuous stirring at room temperature. The performance of adsorption and removal of azo dye congo red by Fe3O4@ZIF-8 was investigated. The effects of initial concentration and contact time, Fe3O4@ZIF-8 dosage and pH on congo red removal were investigated. The characterization of SEM, TEM, XRD, FT-IR and VSM showed that ZIF-8 nanoparticles have been successfully loaded on the surface of Fe3O4 to form a typical core-shell structure with excellent magnetic properties. The experimental results showed that the optimum pH was 6, the dosage of adsorbent was 500 mg·L−1, and the adsorption equilibrium was achieved at the reaction time of 180 min. The adsorption kinetics of congo red on Fe3O4@ZIF-8 was in accordance with the second-order kinetic equation, and the adsorption isotherm followed Langmuir model. Fe3O4@ZIF-8 adsorbent had high selective adsorption performance for congo red and presented good reusability in cyclic adsorption. Therefore, magnetic core-shell metal-organic framework Fe3O4@ZIF-8 had broad application prospects in the removal of congo red dyes as adsorbent.-
Key words:
- magnetic metal organic framework /
- Fe3O4@ZIF-8 /
- congo red /
- adsorption kinetics
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表 1 Fe3O4@ZIF-8对刚果红染料的动力学拟合参数
Table 1. Parameters of kinetic models for CR onto Fe3O4@ZIF-8
初始浓度/
(mg·L−1)qe, exp/
(mg·g−1)一级动力学模型 二级动力学模型 qe, cal/
(mg·g−1)K1 R2 qe, cal/
(mg·g−1)K2 R2 30 60 26 0.021 0.947 61 0.002 25 0.999 50 98 71 0.024 0.978 104 0.000 63 0.995 70 136 124 0.023 0.963 145 0.000 32 0.993 注:qe,exp和qe,cal为平衡吸附量实验值和拟合值。 表 2 Langmuir和Freundlich常数及可决系数
Table 2. Langmuir and Freundlich adsorption constants and correlation coefficients
温度/℃ Langmuir模型 Freundlich模型 qmax /(mg·g−1) b/(L·mg−1) RL R2 Kf /(L·g−1) n R2 25 211 0.135 0.024 0.992 101.21 7.44 0.881 30 327 0.184 0.018 0.998 105.81 4.12 0.934 35 405 0.192 0.017 0.996 112.78 3.39 0.944 -
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