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纳米混合金属氧化物/石墨烯复合物的制备及其活化过硫酸盐降解双酚A的应用
论文作者:童鞋论文网  论文来源:www.txlunwenw.com  发布时间:2019/9/9 8:48:36  

摘要:双酚A(BPA)具有内分泌干扰属性,对生物体的生殖和发育造成严重影响,因此常利用高效便捷的高级氧化法来处理水中BPA污染问题。传统的纳米级催化剂(如贵金属、金属氧化物、金属硫化物等)极易团聚,影响其催化活性,不利于催化降解。近年来,石墨烯基纳米金属氧化物因其粒子分散度高、活性位点多而得到了广泛研究。本文以混合金属氧化物(MMO)为催化活性主体,石墨烯为载体材料制备了高效的新型催化剂(MMO/RGO),并通过XRD、FTIR、Raman、TG、SEM、TEM、BET等对复合物的结构、形貌及组成进行表征,采用紫外-可见光谱仪对MMO/RGO活化过硫酸盐降解BPA的氧化反应进行跟踪,评估了其对BPA的催化降解效率及其循环稳定性,并考察了不同反应条件对催化氧化BPA的影响,主要研究内容如下:

(1)以一步水热法合成了镍钴层状双金属氢氧化物/氧化石墨烯(Ni-Co LDH/GO),采用简便的煅烧法成功制备了Ni-Co MMO/RGO复合物。结构表征显示:平均粒径约为5-10 nm的NiO和Co3O4纳米粒子均匀地分布在具有透明褶皱的还原氧化石墨烯(RGO)表面。对复合物制备条件和BPA降解条件进行了优化,结果显示:当石墨烯含量为15 wt%时,Ni-Co MMO/RGO15%复合物催化性能最优;在中性条件下,当催化剂用量为0.4 g/L,反应温度为25 °C时,40mg/L的BPA去除率达到93.85%。与Ni-Co MMO纯样相比,负载石墨烯后,BPA的去除率提升了47%,说明RGO的引入赋予了Ni-CoMMO/RGO复合物更高的催化活性。反应动力学研究发现,催化剂投加量与反应速率成正比,BPA初始浓度与反应速率成反比。此外,该催化剂表现出良好的循环稳定性能,5次循环后,BPA的去除率仍达到80%。

(2)以金属有机骨架—镍铁类普鲁士蓝(Ni-Fe PBA)为前驱体,在空气中热处理制备了镍铁混合金属氧化物(Ni-FeMMO),再通过一步水热法将金属氧化物成功负载到石墨烯表面,制备了Ni-Fe MMO/RGO复合物。结构表征显示:Ni-Fe MMO由NiO和NiFe2O4组成,呈直径约150 nm的多孔纳米立方体状,比表面积达到113.56 m2·g-1,与石墨烯复合后,比表面积增至138.52 m2·g-1。对复合物制备条件和BPA降解条件进行了优化,结果显示:当石墨烯含量为5 wt%时,Ni-Fe MMO/RGO5%复合物催化性能最优;在中性条件下,当催化剂用量为0.4 g/L,反应温度为25 °C时,40mg/L的BPA去除率达到95%,与Ni-Fe MMO纯样相比,负载石墨烯后,BPA的去除率提升了13%,说明RGO的引入提高了Ni-FeMMO/RGO的分散度,使其暴露出更多的催化活性位点。反应动力学研究发现,催化剂投加量、反应温度与反应速率成正比,BPA初始浓度与反应速率成反比,弱碱性环境有利于反应的进行。该催化剂还表现出可观的循环稳定性能,6次循环后,BPA的去除率仍达到80%。

(3)以金属有机骨架—2-甲基咪唑-67(ZIF-67)为前驱体,通过离子交换在其表面沉积粗糙的Ni-Co LDH纳米片形成ZIF-67@LDH。将ZIF-67@LDH在空气中进行热处理后与石墨烯复合,成功制备了Ni-Co MMO/RGO复合物。结构表征显示:ZIF-67呈直径约1.6 μm的正十二面体结构,ZIF-67@LDH呈正十二面体的蛋黄壳结构,Ni-Co MMO由Co3O4和NiCo2O4组成,呈直径约1 μm的多孔双壳纳米笼结构。对复合物的制备条件进行了优化,结果显示:当石墨烯含量为10wt%时,反应15 min后,40 mg/L的BPA去除率达到96%。除了优异的催化性能之外,Ni-Co MMO/RGO10%复合物还表现出良好的循环稳定性,经5次循环后,BPA的去除率仍达到85%。

此外,对所制备催化剂的催化剂性能进行对比,以BPA氧化的准一级动力学速率常数来衡量不同催化剂的反应活性,得到如下顺序:Co3O4/NiCo2O4-RGO10% > NiO/NiFe2O4-RGO5% > NiO/Co3O4-RGO15%。

Bisphenol A (BPA) has a serious effect on thereproduction and development of the organism due to its property of endocrinedisturbance. Therefore, high-efficiency and convenient advanced oxidationprocesses is often used to treat BPA pollution in wastewater. Traditionalnano-catalysts, such as noble metals, metal oxides, metal sulfides, are easilyagglomerated, which affects their catalytic activity. In recent years,graphene-based nanometal oxides have been widely studied because of its highparticle dispersion and multiple active sites. The structure and morphology ofthe composites were characterized by XRD, FTIR, Raman, TG, SEM, TEM and BET.The catalytic degradation efficiency of the modified graphene-based mixed metaloxide towards BPA was evaluated by UV-Vis. And cycle stability of the compositeswas also investigated. The main studies are as follows:

(1) First, Ni-Co LDH/GO was synthesized byone-step hydrothermal method. After calcination in air, Ni-Co MMO/RGOcomposites were successfully prepared. The structural characterization showsthat Ni-Co MMO, which are consist of NiO and Co3O4 nanoparticles with anaverage particle size of 5-10 nm, are uniformly distributed on the surface ofreduced graphene oxide (RGO) with transparent pleats. The preparationconditions and BPA degradation conditions were optimized. The results show thatNiO/Co3O4-RGO15% composite has the best catalytic performance when the graphenecontent is 15 wt%. Under neutral conditions, when the catalyst dosage was 0.4g/L and the reaction temperature was 25 °C, the degradation rate of BPA (40mg/L) was reached 93.85%. Compared with Ni-Co MMO pure sample, the degradationrate of BPA increased by 47% after loading graphene, indicating a synergisticeffect between Ni-Co MMO and RGO. The reaction kinetics study found that the catalystdosage is proportional to the reaction rate, while the initial concentration ofBPA is inversely proportional to the reaction rate. In addition, the catalystexhibited excellent cycling stability, and the degradation rate of BPA stillreached 80% after 5 cycles.

(2) One of metal-organic framework, Ni-Feprussian blue analog (Ni-Fe PBA), was first prepared as precursor. Aftercalcination in air, Ni-Fe mixed metal oxide (Ni-Fe MMO) was successfullyprepared. Then, the MMO nanoparticles were successfully loaded onto the surfaceof graphene to prepare Ni-Fe MMO/RGO composites by one-step hydrothermalmethod. The structural characterization shows that Ni-Fe MMO is in the form ofa porous nanocubes with a diameter of approximately 150 nm, which consists of NiOand NiFe2O4. The preparation conditions and BPA degradation conditions wereoptimized. The results show that Ni-Fe MMO/RGO5% composite has the bestcatalytic performance when the graphene content is 5 wt%. Under neutralconditions, when the catalyst dosage is 0.4 g/L and the reaction temperature is25 °C, the degradation rate of BPA (40 mg/L) was reached 95%. Compared withNi-Fe MMO pure sample, the degradation rate of BPA increased by 13% afterloading graphene, indicating a synergistic effect between Ni-Fe MMO and RGO.The reaction kinetics study found that the catalyst dosage and reactiontemperature are proportional to the reaction rate, while the initialconcentration of BPA is inversely proportional to the reaction rate. The weakalkaline environment is favorable for the reaction. The catalyst also showedpredominant cycling stability, and the degradation rate of BPA still reached80% after 6 cycles.

(3) ZIF-67@LDH was formed by depositingcoarse Ni-Co LDH nanosheets on the surface by ion exchange using2-methylimidazole-67 (ZIF-67) as a precursor. And then transformed intoCo3O4/NiCo2O4 MMO nanoparticles by thermal annealing in air. Afterward, the MMOnanoparticles are supported on the surface of graphene by one-step hydrothermalmethod to form Co3O4/NiCo2O4-RGO composites.

关键词:混合金属氧化物;石墨烯;过硫酸盐;高级氧化;双酚A

mixed metal oxide; graphene; persulfate;advanced oxidation process; bisphenol A

上一篇:曝气-芽孢杆菌联合处理技术对河道底泥改良和水体修复的研究     下一篇:UiO-66复合材料的制备及其对有机污染物的吸附光催化性能研究
 
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