【作者】 张媛媛；

【导师】 柳广飞；

【作者基本信息】 大连理工大学 ， 环境科学与工程， 2020， 硕士

【摘要】 氧氟沙星（OFX）是广泛应用于医疗、养殖和畜牧等行业中的喹诺酮类抗生素,其在生产和使用过程中进入环境会造成潜在的生态风险。研究表明,以含铁矿物等作为催化剂的非均相类芬顿氧化技术能够用于抗生素的降解。然而,含铁矿物催化的非均相类芬顿体系中Fe（III）/Fe（II）循环缓慢,提高Fe（III）/Fe（II）转化效率成为改善非均相类芬顿体系催化活性的关键。研究表明,向类芬顿体系中添加某些还原剂和配合剂能够促进Fe（III）/Fe（II）转化效率,提高类芬顿降解效果。作为限氧条件下热解生物质的产物,生物炭（biocahr,BC）来源广泛、成本低廉,且具有良好的吸附及配合金属离子能力和氧化还原活性。有鉴于此,本研究探索利用BC强化针铁矿（Gt）催化类芬顿反应降解OFX。利用小麦秸秆在300℃或600℃条件下分别热解制备生物炭样品BC300和BC600。将上述BC样品加入Gt类芬顿体系可显著促进体系氧化降解OFX。在4 h内,Gt/H₂O₂和BC600/H₂O₂体系中只有38.4%和48.4%的OFX（20 mg/L）被去除,而在Gt/BC600/H₂O₂体系中,OFX去除效率大于94.0%。Gt/H₂O₂、BC600/H₂O₂和Gt/BC600/H₂O₂体系的准一级动力学速率常数分别为0.12、0.16和0.72 h^-1,表明Gt-BC共存类芬顿体系中发生了协同催化降解。与BC300相比,在较高的热解温度下产生的BC600可以更好地促进OFX的降解。在Gt-BC共存类芬顿体系中,当Gt浓度为0.2 g/L,BC600浓度为0.3 g/L,H₂O₂浓度为2 mM,pH为3时,OFX的降解效果最佳,4 h内可达94.2%。在连续四次重复使用过程中,Gt/BC600/H₂O₂体系对OFX的去除效率分别为94.2%,87.8%,82.4%和75.5%,表明其具有较好的催化降解稳定性。自由基淬灭实验和电子自旋共振光谱分析结果表明,·OH为Gt/BC600/H₂O₂体系中的主要氧化剂。Gt/BC600/H₂O₂体系中的·OH产率和H₂O₂利用效率均高于Gt/H₂O₂和BC600/H₂O₂体系。利用H₂O₂预处理以消除BC600表面的持久性自由基（PFRs）,与对应的添加BC600的体系相比,添加BC600_depleted-24的类芬顿体系中OFX的去除效率均降低了约11%,表明BC中的PFRs参与了OFX的氧化降解。Fe物种分析、X射线光电子能谱和红外光谱分析结果表明,尽管BC不能直接还原Gt中的Fe（III）,但其通过表面羧基配合Fe（III）,加速Fe（III）/Fe（II）转化效率,从而促进Gt-BC共存类芬顿体系中·OH的产生和OFX的降解。HPLC-MS分析检出OFX降解过程中的8种降解产物,推测在Gt-BC共存类芬顿体系中OFX的降解路径包括脱甲基、脱氟、氢损失和羟基化等反应。更多还原

【Abstract】 Ofloxacin（OFX）is one kind of quinolone antibiotic that has been widely used in medical,breeding and animal husbandry industries.The entering of ofloxacin into environments during its production and application brings potential ecological risks.Iron-bearing mineral-catalyzed heterogeneous Fenton-like oxidation technology can be used for antibiotics degradation.However,the cycling of Fe（III）/Fe（II）in heterogeneous Fenton-like systems is slow.Improving Fe（III）/Fe（II）conversion efficiency is the key issue for promotion of the catalytic activity of heterogeneous Fenton-like systems.It has been suggested that the addition of reducing and complexing agents could improve the Fe（III）/Fe（II）conversion efficiency and catalytic activity in Fenton-like systems.Biochar（BC）is a carbon-enriched material derived from the pyrolysis of biomass under limited oxygen.BC is not only widely sourced and low cost,but also has good redox activity.It can adsorb and complex with metal ions.Here,this study explored whether BC could promote OFX degradation in goethite（Gt）catalyzed Fenton-like system.BC300 and BC600 samples were prepared by pyrolysis of wheat straw at 300℃ and600℃,respectively.It was found that BC greatly stimulated the degradation of OFX in Gt-mediated Fenton-like system.In 4 h,while only 38.4%and 48.4%OFX（20 mg/L）were removed in Gt/H2O2 and BC600/H2O2 systems,the removal efficiency reached over 94.0%in Gt/BC600/H2O2 system.And the pseudo-first-order rate constant of Gt/H2O2,BC600/H2O2and Gt/BC600/H2O2 systems were 0.12,0.16 and 0.72 h^-1,respectively,indicating the occurrence of synergistically catalytic degradation.BC600 showed better stimulation effects than BC300.Through investigation of the impacts of factors like BC concentration（0-0.4g/L）,H2O2 concentration（0-4 mM）and pH condition（2-7）,the optimum reaction condition of Gt/BC600/H2O2 system was determined to be 0.2 g/L Gt,0.3 g/L BC600,2 mM H2O2 and pH 3,which led to 94.2%OFX degradation within 4 hours.Around 94.2%,87.8%,82.4%and75.5%OFX were removed in a four-round repeated treatments,which indicated the good stability of catalytic OFX degradation in the Gt/BC600/H2O2 system.The results of free radical scavenging experiment and electron spin resonance spectrum analysis showed that·OH was the main oxidant in the Gt/BC600/H₂O₂ system.Both the H₂O₂utilization efficiency and the·OH production in the Gt/BC600/H₂O₂ system were higher than those of Gt/H2O2 and BC600/H2O2 systems.BC600 was pre-treated with H2O2 to partially eliminate the persistent free radicals（PFRs）on its surface.The OFX removal efficiency in Fenton-like systems added with BC600 depleted-24 were around 11%lower than those of their counterpart systems added with pristine BC600 samples,indicating that the PFRs of BC participated in the oxidative degradation of OFX.The results of Fe species analysis,X-ray spectroscopy and FTIR analysis showed that although BC could not directly reduce the Fe（III）in Gt,it improved the cycling of Fe（III）/Fe（II）through complexing with Fe（III）by its carboxyl group.HPLC-MS analysis detected 8 OFX degradation products in the Gt/BC600/H2O2 system.It was speculated that the potential pathways of OFX degradation in the Gt-BC coexisting Fenton-like system included demethylation,defluorination,hydrogen loss and hydroxylation reactions.更多还原