【作者】 丁耀彬；

【导师】 朱丽华；

【作者基本信息】 华中科技大学 ， 材料物理与化学， 2013， 博士

【摘要】 基于硫酸根自由基(SO4·-)的高级氧化过程具有氧化能力强、矿化程度高、氧化剂本身稳定性好、氧化剂利用率高、反应不受pH影响、抗碳酸盐和氯化物等无机盐能力强等优点,在有机污染物的降解中有着良好的应用前景。应用S04·-高级氧化技术的关键是寻找高效活化过硫酸盐产生SO4·-的方法和催化剂。常规的活化方法包括紫外光、热、微波等物理手段和过渡金属离子等化学方法。考虑物理方法能耗高、成本高,而过渡金属离子活化可以在常温、常压下快速进行,而且不需要额外的能量,因此,过渡金属离子活化过硫酸盐的研究更受关注。在过硫酸盐中,过一硫酸盐(PMS, HSO5-)的分子结构不对称,多种过渡金属离子都可以将其活化,其中以Co2+的活化效果最好。LCo2+的毒性限制了该体系的广泛应用,科学家们不得不开发载钴多相催化剂。载钴多相催化剂虽能有效活化PMS产生高活性的SO4·一降解有机污染物,但却仍存在钴离子溶出量大、稳定性差等突出问题,故开发高效、稳定的多相催化剂是当前环境催化领域研究的热点。本文主体考察了纳米氧化钴和氧化铋复合物(Co3O4-Bi2O3)、纳米铁酸铜(CuFe2O4)和微米具有赤铜铁矿结构的CuFeO2催化活化PMS及在有毒有机污染物降解方面的应用。主要研究内容包括：(1)提出了一种制备纳米Co3O4-Bi2O3复合物催化剂的方法,采用这一新方法制备了纳米Co304-Bi203复合物催化剂,研究了其催化活化PMS并降解多种有机污染物的过程。制备方法涉及到反相共沉淀和热处理的联用。研究发现,在纳米Co3O4-Bi2O3复合物中,Bi和Co之间存在强的相互作用,这种相互作用增大了复合物表面的羟基氧含量。与纳米CO3O4(?)目比,纳米Co3O4-Bi2O3复合物对PMS分解反应的催化活性更强,更有利于有机污染物的氧化降解。在相同的催化剂(0.05g L-1)和PMS用量(0.5mmolL-1)下,Co3O4-Bi2O3-PMS体系中亚甲基蓝(MB,20μmol L-1)降解遵循一级反应动力学,速率常数k为0.361min-1,是Co3O4-PMS体系中表观速率常数k (0.042min-1)的8.6倍。同时,这种相互作用还加强了纳米Co3O4-Bi2O3催化剂的稳定性。在酸性条件(pH3.2-3.4)下,0.05g L-1Co3O4-Bi2O3的钴离子溶出量为43μg L-1,远小于相同条件下纳米Co3O4的钴离子溶出量(158μgL-1)。由于Co3O4-Bi2O3具有优良的化学稳定性,它能够多次循环使用。(2)提出了纳米CuFe2O4的溶胶-凝胶制备法,并以此构建了纳米CuFe2O4-PMS的新型高级氧化体系。纳米CuFe2O4是一种非钴类的PMS活化剂,可克服载钴多相催化剂中钴溶出的缺点。研究发现,在CuFe2O4量为0.1g L-1,PMS浓度为0.2mmol L-1的条件下,CuFe2O4-PMS体系在30min内对10mg L-1四溴双酚A(TBBPA)的降解率达到了99%。当PMS浓度提高到1.5mmol L-1时,反应180min后,TOC去除率达到了56%,脱溴率达到了67%。用醇淬灭试验证实了在CuFe2O4-PMS体系中对TBBPA降解起主导作用的自由基为S04·-。对反应前后CuFe2O4表面Cu和Fe的结合能的分析发现纳米CuFe2O4表面Cu和Fe都参与了PMS的活化,据此,提出了纳米CuFe2O4活化PMS产生SO4·-的机理。最后,用HPLC及LC-MS技术,检测了CuFe2O4-PMS体系降解TBBPA的中间产物,并给出了SO4·-降解TBBPA的机理。(3)为了进一步提高Cu-Fe氧化物多相催化活化PMS的性能,提出了用含亚铜Cu+的微米CuFeO2作为活化剂活化PMS降解有机污染物的新方法。研究发现,与Cu2O、Fe2O3和CuFe2O4催化剂相比,CuFeO2表现出了更高的催化活性。当CuFeO2微米颗粒投加量为0.5g L-1,PMS的用量为0.2mmol L-1时,30min内对10mg L-1的TBBPA的降解率达到了100%,高于Fe2O3和Cu2O催化剂对TBBPA的降解率(24%和66%)。纳米CuFeO2和纳米CuFe2O4活性对比实验表明,纳米CuFeO2催化剂在TBBPA降解、TOC去除和TBBPA脱溴上比纳米CuFe2O4催化剂都更高效。当催化剂用量和PMS为0.5g L-1和1.5mmol L-1,60min内,CuFeO2-PMS-TBBPA体系中TOC去除率和脱溴率分别达到了75%和81%,高于CuFe2O4-PMS-TBBPA体系的TOC去除率和脱溴率(62%和74%)。此外,微米CuFeO2催化剂易于回收,活性稳定,可重复利用,可广泛应用于实际污水的处理。最后,在总结了上述研究结果的基础上,为了将相关工作进行延伸,本文针对已研究的几种新型环境催化剂的研究进行了展望,期待通过可见光光催化的引入、多相类Fenton催化体系的构筑以及酚类增效媒介物的引入等措施进一步强化这些催化剂的催化性能,扩展其在环境催化领域中的应用。更多还原

【Abstract】 Sulfate radical (SO4-) based advanced oxidation technologies (AOTs) have a good application prospect in the field of wastewater treatment due to the stronger oxidizing ability of sulfate radicals (standard potential2.5-3.1V) than hydroxyl radicals (2.2-2.7V), the high mineralization rate, the persistent nature of the precursors (persulfate and peroxymonosulfate (PMS)) compared to H2O2, the high oxidant utilization, wide operating pH range, and its strong endurability to inorganic salts such as carbonate and chloride in practical aqueous enviornment. The key of SO4-based AOTs is to develop highly efficient activation ways and catalysts of persulfate and PMS. The generally used activation ways include physical methods such as light, heating and microwave irradiation and chemical methods by using transition metal ions as activators. Compared to disadvantages of high energy consuming by using physical activation ways, chemical activation can be achieved under ambient conditions and thus has great attention in the activation of persulfate and PMS. Among the two oxidants, PMS has an unsymmetric structure for only one H is replaced by SO3and can be more easily activated by versatile transition metal ions. Among these transition metal ions, Co(Ⅱ) is the most effective catalyst of PMS activation for the production of sulfate radicals. Due to the toxicity of Co(Ⅱ) ion, heterogeneous immobilized cobalt catalysts were developed. However, many of them show high cobalt-leaching and low catalytic stability. Thus, to develop highly catalytic activity and highly stable heterogeneous catalysts for the activation of PMS is a currently hot research spot in the field of environmental catalysis. The aim of this dissertation is to develop heterogeneous catalysts including Co3O4-Bi2O3nanocomposites, CuFe2O4nanoparticles and CuFeO2microparticles to improve the activation ability and the oxidant efficiency of PMS for removal of toxic organic pollutants. The major contents are described as follows:(1) An innovative method involving the couple of reverse co-precipitation method and post-calcination for preparing Co3O4-Bi2O3nanocomposite oxides were developed and the prepred Co3O4-Bi2O3nanocomposite oxides as heterogenous catalysts of PMS for the degradation of several organic pollutants were investigated. It was found there was a strong interaction between Bi and Co components in the nanocomposite, which was found to enhance surface hydroxyl oxygen content and in favor of the formation of Co(Ⅱ)-OH complexes. Co3O4-Bi2O3nanocomposite oxides showed stronger catalytic activity for the heterogeneous activation of PMS and the degradation of organic pollutanst than CO3O4. With the addition0.05g L-1catalysts of and0.5mmol L-1PMS, the Co3O4-Bi2O3nanocomposite oxides produced fast and full degradation of methylene blue (MB,20μmol L-1) with the apparent rate constant of0.36min-1, being8.6folds of that (0.042min-1) over nano-Co3O4. The cobalt leaching to43μg L-1was observed for0.05g L-1Co3O4-Bi2O3nanocomposite oxides, being much less than that (158μg L-1) from Co3O4in the acidic aqueous solutuion (pH3.2-3.4). Due to the excellent chemical stability, Co3O4-Bi2O3nanocomposite oxides show favorable catalytic performance during three successive cycles.(2) A sol-gel method was developed to prepare CuFe2O4nanoparticles and an innovative adcanced oxidation system of CuFe2O4/PMS was constructed. CuFe2O4nanoparticles is a cobalt-free catalyst for the activation of PMS, thus, the cobalt leaching can be avoided. It was found the added tetrabromobisphenol A (TBBPA,10mg L-1) was almost completely removed (with a removal of99%) in30min by using0.1g L CuFe2O4and0.2mmol L-1PMS. With higher addition of PMS (1.5mmol L-1), the degradation yielded a TOC removal of56%and a TBBPA debromination ratio of67%. Radical quenching tests proved that SO4-radicals were the main reactive species. XPS characterization results of the fresh and used CuFe2O4indicated the highly catalytic activity could be attributed to a catalytic mechanism involving both Cu(Ⅱ) and Fe(Ⅲ) in CuFe2O4.Based on the HPLC and LC-MS analysis of the degradation intermediates in the CuFe2O4/PMS system, a detail mechanism for SO4-induced TBBPA degradation was proposed.(3) To further improve the catalytic ability of Cu-Fe compounds, Cu+-bearing CuFeO2microparticles were synthesized and characterized as a new activator of PMS for degradation of organic pollutants. It was found CuFeO2exhibited much higher catalytic activity towards degradation of TBBPA in the presence of PMS in comparison with Fe2O3, Cu2O and CuFe2O4as catalysts. The addition of CuFeO2microparticles (0.5g L-1) induced a TBBPA degradation removal of100%in30min in the presence of0.2mmol L-1PMS, higher than that (25%and66%in30min) by using Fe2O3and Cu2O particles as catalysts under the similar conditions. Furthermore, CuFeO2nanoparticles showed better performances in the TBBPA degradation, TOC removal and debromination than CuFe2O4nanoparticles. By adding1.5mmol L-1PMS,62%TOC removal and74%debromination of TBBPA were observed in the case of0.5g L-1CuFe2O4nanoparticles in60min, which were increased to75%(TOC removal) and81%(debromination ratio) in the case of0.5g L-1CuFeO2nanoparticles. Moreover, CuFeO2microparticles also exihibited excellent catalytic stability and easy recyclability, thus, the method based on the catalytic activation of PMS by CuFeO2microparticles has promising potentials in the application in the field of pollution control as a green oxidation process.Finally, on the basis of the above research results, new possible application and the related investigation of the three innovative catalysts are prospected. The introduction of visible light, the construction of Fenton-like system and phenolic compounds modified Fenton-like system is anticipated to further enhance catalytic activity of these catalysts and extend their application in the field of environmental catalysis.更多还原