【期刊】超声辅助水热合成Fe/Cu掺杂NaP分子筛芬顿氧化脱除有机染料过程协同作用研究

东北石油大学陈彦广教授团队近日于国际分离纯化领域著名期刊Separation and Purification Technology（JCR 1区Top，中科院2021升级版分区：工程技术1区Top期刊，2021影响因子：9.136）上发表了题为“Effective Removal of Organic Dyes Using the Ultrasonic-assisted Hydrothermal Synthesis of NaP Zeolite Doping Cu or Fe in Fenton-like Oxidation Systems”的文章（Volume 299, October 2022, 121767, Available online 21 July 2022）。该文章第一作者为东北石油大学博士研究生张亚男；共同通讯作者为东北石油大学张梅副教授和陈彦广教授。

【图文摘要｜Graphical abstract】

【研究亮点｜Highlights】

• 在NaP分子筛晶体生长过程中，超声波的引入提高了硅铝组分的转化率。

• 超声波协同有机络合法可实现NaP分子筛中原位掺杂过渡金属Cu/Fe。

• Fe/Cu掺杂NaP分子筛在芬顿氧化脱除有机染料方面具有优异的性能。

• Ultrasonic enhances the conversion of Si and Al components in preparing NaP zeolite.

• Complexation coordinated with ultrasonic facilitates Cu or Fe doping in NaP zeolite.

• NaP zeolite doped with Fe or Cu owns excellent removal performance for organic dyes.

【文章简介｜Introduction】

有机污染物废水因其COD高和降解难而成为水体治理的一个难点，芬顿氧化法是处理难降解有机废水的有效方法，其主要包括均相催化和非均相催化，非均相催化具有催化剂易分离和循环使用等优势，构筑高效非均相催化剂体系是提高有机物氧化脱除的关键。NaP分子筛具有独特的骨架结构和较高的产率，作为非均相催化体系的载体具有较好的前景。在本项工作中，以粉煤灰为原料，通过分级处理提取硅铝组分，采用超声强化水热合成的传质作用，提高硅铝组分转化和调控产物晶粒尺寸，通过有机络合法在NaP分子筛水热合成过程实现Cu/Fe的原位掺杂，通过吸附和催化氧化协同作用实现了亚甲基蓝（MB）和甲基紫6B（MV-6B）的高效脱除，为有机废水的处理提供了理论基础和技术支持。

The higher COD value and uneasy degradation of the wastewater containing the organic dyes have become a difficult problem. The Fenton-like oxidation method, as the effective method for the disposal of the wastewater containing the organics, mainly includes homogeneous catalysis and heterogeneous catalysis. The heterogeneous catalyst has easy separation and recycling advantages, and the key to enhancing the oxidation removal of organics is the building of an effective heterogeneous catalyst system. In this work, coal fly ash was selected as the raw material to extract the silicon and aluminum sources via the grading extraction method. The higher conversion rate of silicon and aluminum components and the regulation of crystal grain size were accomplished through the enhanced mass transfer of ultrasonic-assisted hydrothermal synthesis. The complex method was employed to realize the in-situ doping of Cu/Fe during the hydrothermal synthesis of NaP zeolite. The efficient removal of methylene blue (MB) and methyl violet-6B (MV-6B) was realized through the synergy interaction of adsorption and catalytic oxidation, which provides the theoretical basis and technical support for the treatment of wastewater containing the organics.

1. 超声强化传质实现合成过程调控

超声波的引入促进了无定形硅铝酸盐解聚与结构单元聚合间的平衡态形成，硅铝组分处于过饱和态，由此硅组分和铝组分转化率增大，分别由66.46%和73.75%增大到84.68%和95.25%。同时多相间的扩散层厚度也通过强化传质有所减小。在分子筛结晶度相当时，晶化温度从120℃下降到90℃，晶化时间从8 h缩短至4 h，产物的n(SiO₂)/n(Al₂O₃)从2.0增加到4.0。

1. Regulation of the synthesis process via the ultrasonic-enhanced mass transfer

The introduction of ultrasonic promoted the formation of an equilibrium state between the depolymerization of amorphous aluminosilicates and the polymerization of structural units. The silicon and aluminum components were in a supersaturated state so that the conversion rates of silicon and aluminum components increased from 66.46%. and 73.75% to 84.68% and 95.25%, respectively. Meanwhile, the thickness of the diffusion layer between the two phases was also reduced by enhancing the mass transfer. When the crystallinity of NaP zeolite was equivalent, the crystallization temperature decreased from 120℃ to 90℃, the crystallization time was shortened from 8 h to 4 h, and the n(SiO₂)/n(Al₂O₃) of the product increased from 2.0 to 4.0.

图1 超声波辅助水热合成NaP分子筛的晶化过程

Fig.1  Crystallization process of NaP zeolite via ultrasonic-assisted hydrothermal synthesis

2. Fe/Cu金属原位掺杂

采用络合法进行原位掺杂Fe和Cu，可保持较高的结晶度，其中Cu-NaPultra为94.14%和Fe-NaPultra为92.37%，同时其粒径大小较均一，约为2 μm。如图2中Fe-NaPultra和Cu-NaPultra的HRTEM图像，展现出良好的排列和晶格结构，掺杂的Fe和Cu分散较均匀，SAED图像中的衍射环表明Fe-NaPultra和Cu-NaPultra由微小的晶体粒子聚集组成。

2. In-situ doping of Fe/Cu metals

The in-situ doping of Fe and Cu in NaP zeolite by the complex method could maintain higher crystallinity, in which the crystallinity of Cu-NaPultra was 94.14% and that of Fe-NaPultra was 92.37%. Besides, the grain size of crystals was more uniform. The HRTEM images of Fe-NaPultra and Cu-NaPultra in Fig. 2 showed good arrangement and lattice structure, and the doped Fe and Cu were uniformly dispersed. The diffraction rings in the SAED image indicated that Fe-NaPultra and Cu-NaPultra were composed of the aggregation of tiny crystal particles.

图2 掺杂Fe/Cu的NaPultra分子筛表征结果：（a，b）不同方法制备的XRD图谱；（c）络合法制备掺杂Fe/Cu的NaPultra晶体形态；（d，e）络合法制备Fe-NaPultra和Cu-NaPultra的XRD谱图、粒度分布、SEM、HRTEM和SADE图像。

Fig. 2  Characterization of NaPultra zeolites doped with Fe or Cu:(a, b) XRD patterns using different methods and (c) Crystal morphology of NaPultra zeolites doped with Fe or Cu using the complexation method; (d, e) XRD patterns, particle size distribution, SEM, HRTEM, and SADE images of Fe-NaPultra and Cu-NaPultra using the complexation method.

3. 吸附和催化氧化协同作用高效脱除有机染料

有机染料通过NaP分子筛孔道和电荷引力吸附在M-NaPultra上，与反应过程中产生的羟基自由基（HO•）进行催化氧化，随着反应的进行，活性位点因有机物降解而逐渐被释放出来，为后续氧化反应持续进行提供空间，从而实现有机染料的高效降解。当MB和MV-6B浓度为50 mg/L，pH=5.0，Cu-NaPultra为2.5 g/L，温度为25℃时，反应时间为30 min时，MB脱除率为93.22%，MV-6B脱除率可达为98.71%。

3. Synergistic effect of adsorption and catalytic oxidation for efficient removal of organic dyes

Organic dyes were adsorbed on M-NaPultra through the channels and charge attraction of NaP zeolite and underwent catalytic oxidation with the hydroxyl radicals (HO•) generated during the reaction. As the reaction progressed, the active sites were gradually released due to the degradation of organics, which provides the reaction position for the continuous proceeding of subsequent oxidation reactions so as to achieve the efficient degradation of organic dyes. When the concentration of MB and MV-6B was 50 mg/L, pH=5.0, Cu-NaPultra was 2.5 g/L, the temperature was 25℃, and the reaction time was 30 min, the removal rate of MB was 93.22%, and the removal rate could reach 98.71%.

图3 M-NaPultra类芬顿催化剂对有机染料的可能氧化机理

Fig. 3  Possible oxidative mechanism of organic dyes by M-NaPultra Fenton-like catalysts

【主要结论｜Conclusions】

综上所述，在本项工作中，通过超声波强化水热合成过程的传质作用，提高了硅铝组分转化率，并可在一定程度上调控NaP分子筛晶粒尺寸。获得了络合法对NaP分子筛原位掺杂Fe/Cu的影响规律。构筑NaP分子筛非均相芬顿催化体系，通过M-NaPultra独特的骨架结构的有效吸附和活性物种HO•的催化氧化的协同作用，实现有机染料的高效脱除，为有机废水处理提供了理论依据，具有潜在的应用价值。

To sum up, in this work, the mass transfer of ultrasonic-assisted hydrothermal synthesis enhanced the conversion rate of silicon and aluminum components and could regulate the grain size of NaP zeolite crystals to a certain extent. In addition, the effect of the complexation method on the in-situ doping of Fe/Cu in NaP zeolite was obtained. The construction of a heterogeneous Fenton catalytic system of NaP zeolite achieved the efficient removal of organic dyes through the synergistic effect of the effective adsorption of M-NaPultra's unique skeleton structure and the catalytic oxidation of active species HO•, which provides a theoretical basis for the disposal of the wastewater containing the organics and has potential application value.

【原文信息】

【原文链接】

https://doi.org/10.1016/j.seppur.2022.121767

【主要作者介绍】

【第一作者】

张亚男（博士研究生）

工作单位：东北石油大学化学化工学院

邮件地址：[e-mail]

【通讯作者】

张梅（副教授）

工作单位：东北石油大学化学化工学院

邮件地址：[e-mail]

陈彦广（教授）

工作单位：东北石油大学化学化工学院

邮件地址：[e-mail]

通讯作者：张梅，副教授，硕士生导师。美国伦斯勒理工学院公派访问学者。主要从事高分子膜材料的结构设计与可控制备、污染物资源化利用等方面的应用基础研究。在国内外学术期刊发表学术论文20余篇，获得国家发明专利授权7项，参与完成国家973/863计划项目、省部级科研项目7项，获省部级科技奖励3项。

陈彦广，“龙江学者”特聘教授，博士生导师，黑龙江省杰出青年基金获得者，黑龙江省青年科技奖获得者，黑龙江省石油与天然气化工重点实验室副主任，黑龙江省石油化工标准化技术委员会副秘书长，黑龙江省化工学会常务理事。主要从事催化材料设计及合成过程调控和污染物控制与资源化等方向的应用基础研究。在Appl. Catal. B、J. Hazard. Mater.、J. Clean. Prod.、Fuel等学术期刊发表SCI论文50余篇；获中国授权发明专利42项；主持国家自然科学基金项目2项，省部级基金和科技攻关项目10余项；获得省部级科技进步二等奖2项和技术发明二等奖1项。

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