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基于过硫酸氢钾活化的催化剂构筑及机理研究
Alternative TitleThe construction of heterogeneous catalysts and the study of mechanism for peroxymonosulfate activation
王彦斌
Subtype博士后
Thesis Advisor赵旭
2018-02-08
Degree Grantor中国科学院生态环境研究中心
Place of Conferral北京
Degree Name工学
Degree Discipline环境工程
Keyword过硫酸氢钾 单线态氧 硫酸根自由基 有序介孔碳,石墨化氮化碳 Singlet Oxygen Sulfate Radicals Ordered Mesoporous Carbon Graphic Carbon Nitride peroxymonosulfate
Abstract

     水中难降解有机污染物的氧化 去除是环境 领域关注的 问题之一。 我们知道过硫酸盐能够通过多种方式被 活化产生 硫酸根自 由基( SO 4 ·-) 。 近年来 过硫酸盐 活化在 水体净化 、 土壤或地下水修复等领域展现出巨大的应用前景而备受关注 。然而,目前报道的异相催化剂活性较低,相关 的催化反应机理 有待进一步研究。本课题选择过硫酸氢钾( PMS )为活化对象,以提高有机污染物降解效率为目的结合自由基屏蔽实验、光谱及电化学等手段,研究 PMS 活化过程中的反应机理。主要研究内容和结果如下所示:

     (1) “一锅法”制备了氧化 钴掺杂 的有序 介孔碳 Co OMC 复合催化剂 ,它可以高效 活化 PMS 降解苯酚 ,其催化活性明显高于文献报道的 Co 3 O 4 和 CoFe 2 O 4 。同时 对七 种典型 的 难降解有机污染物 均表 现出 较 好的 去除效果 。 Co OMC /PMS体系的氧化性能与溶液 pH 有 关 碱性 条件 有利于有机污染物 的氧化去除 。 HCO 3 、Cl 和腐殖酸等可以促进苯酚的降解,而 H 2 PO 4 则对苯酚降解有一定的抑制作用。Co OMC/PMS 体系中同时存在有多种 活性氧物种 ,包括  OH 、 SO 4 、 O 2 · 和 1 O 2 。在初始 pH 为 6.0 时 苯酚降解主要归因于 O 2 · 和 1 O 2 的作用 初始 pH 为 1 1.0时  OH 和 SO 4
 也 起到非常重要的作用 。

    (2) 采用软模板法制备了硼掺杂 的有序介孔碳 B OMC )催化剂。 相比于
OMC 该催化剂 活化 PMS 降解双酚 A 的 催化活性明显 提高 。硼的掺杂提高了
OMC 的比表面积和孔径,增强了 OMC 对双酚 A 的吸附作用。硼的掺杂在 OMC表面引入了 BC 2 O BCO 2 物种 其 作为 催化 PMS 的活性中心,可以高效分解 PMS产生 O 2 和 1 O 2 。

    (3) 制备了 单原子 Ag 掺杂的介孔 g C 3 N 4 Ag mpg C 3 N 4 复合催化剂, PMS显著提高了光催化降解 双酚 A 的活性 这归功于以下几点 1 Ag 的掺杂减小了 g C 3 N 4 的带隙宽度 促进了可见光的吸收 2 g C 3 N 4 导带上的光生电子可以传递给具有较低费米能级的 Ag ,促进光生电子 空穴的分离;( 3 PMS 起到电子受体的作用,促进光生电子 空穴分离,且 可以 被光生电子激发产生 SO 4 · ,极大地提高了光 催化 氧化 的 能力。

(4) 通过简单的 KBH 4 还原的方法制备了 Pd 纳米粒子修饰的 g C 3 N 4 Pd/gC 3 N 4 复合催化剂 。 该催化剂对活化 PMS 降解双酚 A 表现出优异的催化活性在 0.1 g/L 催化剂投加量、 PMS 浓度 1.0 mM 的条件下, 20 mg/L 的双酚 A 在 60min 内的去除率可以达到 91% 。根据自由基屏蔽实验、 ESR 及自由基定量结果发现, Pd/g C 3 N 4 /PMS 体系中主要的活性氧物种为 O 2 · 和 1 O 2 ,而不是 ·OH 和 SO 4 · 。

Other Abstract

      The effective removal of refractory organic is one of the difficult problem in environmental field. As we know, sulfate radicals (SO 4 · ) can be generated by activation of persulfate. Recently, the activation of persulfate has been applied to various fields such as water purification , s oil and groundwater remediation and has attracted increasing attention. However, the catalytic activity of reported heterogeneous catalysts is not good enough and the catalytic mechanism should be further investigated. In this work, we tried to improve the catalytic activity for peroxymonosulfate (PMS) activation and investigate the catalytic mechanism by using radical quenching experiment, spectr al and electrochemical methods. The main contents and results are exhibited below:

    1. F irstly , cobalt doped ordered mesoporous carbon Co OMC) composite catalyst was prepared by a ‘one pot’ method. Co OMC presented higher catalytic activity for PMS activation compared with the reported Co 3 O 4 and CoFe 2 O 4 . Seven typical refractory organics can be efficiently removed by Co OMC/OMS system. The oxidizability of Co
OMC/PMS system depended on the pH of solution and the removal of phenol at basic condition was higher than acid condition. Bicarbonate, chloride ion and humic acid presented the positive effect on the r emoval of phenol, while phosphate showed the negative effect on the removal of phenol. The results showed various reactive oxygen species (ROS) such as hydroxyl radical (  OH), sulfate radical (SO 4 ), superoxide radical
(O 2 ) and singlet oxygen 1 O 2 ) were involved in the degradation of phenol in CoOMC/PMS system. O 2  and 1 O 2 played the main role on the removal of phenol at initial pH 6.0, while  OH and SO 4  also played an important role on the removal of phenol at initial pH 11.0.

    2. S econdly, boron doped ordered mesoporous carbon (B OMC) was prepared by a soft templet strategy. Compared with OMC, the catalytic activity of B OMC for PMS activation was greatly enhanced. The introduction of boron atoms promoted the BET specific surface area
pore size and the adsorption of OMC for bisphenol A (BPA). The catalytic active sites on B OMC surface was inferred to be BC 2 O BCO 2 species, which decomposed PMS to generate O 2  and 1 O 2。

3. S ingle atom Ag dispersed mesoporous graphic carbon nitride (Ag mpg C 3 N 4 ) was prepared and used as a visible photocatalyst for the degradation of BPA. In the presence of PMS, the removal efficiency of BPA was greatly increased. The enhancement of photocatalytic activity can be ascribed to three reasons: (i) the band gap of g C 3 N 4 was narrowed and the absorbing ability of g C 3 N 4 for visible light was enhanced with the
introduction of Ag atoms; (ii) due to the lower Fermi level of Ag compared with the conduction band of g C 3 N 4 the photogenerated electron can transfer to Ag atom and results in the promot ed separation efficiency of photogenerated electron hole ; (iii) a electron acceptor, could accept the photogenerated electron of g C 3 N 4 and be activated to produce SO 4
 , resulting in the enhancement of photocatalysis efficiency.

4. Pd nanoparticles modified graphic carbon nitride ( Pd/g C 3 N 4 catalyst was prepared by a simple KBH 4 reduction method. Pd/g C 3 N 4 present excellent catalytic activity of PMS activation for the degradation of BPA. At the condition of 0.1 g/L catal yst dosage, 1.0 mM PMS, 91% of BPA (20 mg/L) could be removed in 60 min. According to the results of
radical quenching experiment, electron spin resonance and quantitative experiment of superoxide radical, it can be concluded that the main ROS were O 2 · a nd 1 O 2 instead of ·OH and SO 4 ·

 

 

Pages85
Document Type学位论文
Identifierhttp://ir.rcees.ac.cn/handle/311016/41541
Collection环境水质学国家重点实验室
Recommended Citation
GB/T 7714
王彦斌. 基于过硫酸氢钾活化的催化剂构筑及机理研究[D]. 北京. 中国科学院生态环境研究中心,2018.
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