【作者】 陈晨；

【导师】 张晟瑀；

【作者基本信息】 吉林大学 ， 工程硕士（专业学位）， 2023， 硕士

【摘要】 四环素作为我国使用最广泛的抗生素在水体中被频繁检出,其造成的环境危害引起了人们的广泛关注。基于过硫酸盐的高级氧化技术（SR-AOPs）是有效去除水体中四环素类污染物的手段之一。鉴于生物炭的环境友好特性和丰富的孔隙结构,其在非均相SR-AOPs领域具有广阔的应用前景。生物炭活化过硫酸盐降解污染物的机理包括自由基途径和非自由基途径。其中,非自由基途径相对温和,且对阴离子以及背景天然有机物质（NOMs）具有抗性。目前研究发现,大多数原始生物炭的催化性能不够理想。氮掺杂能有效改善原始生物炭对过硫酸盐的催化活化。然而,影响氮掺杂生物炭催化活性的主要结构及其活化过硫酸盐机制尚不明确,这限制了氮掺杂生物炭的定向设计。本研究以盐酸四环素（TCH）为目标污染物,以玉米秸秆粉末为原料,三聚氰胺为氮源,在不同热解温度下制备一系列原始生物炭（BC）及氮掺杂生物炭（N-BC）,探究生物炭结构变化对其活化过二硫酸盐（PDS）性能的影响。此外,利用电子顺磁共振（EPR）、猝灭实验、电化学分析技术、高效液相色谱-质谱技术（LC-MS）等解析BC及N-BC活化PDS的作用机制,为氮掺杂生物炭的定向设计提供理论基础。本研究主要结果如下:（1）氮掺杂显著改善了生物炭材料的物理性质和化学结构特性,其中,900℃下制备的N-BC900表现出最高的比表面积（1357 m²/g）,最高的石墨化程度和羰基基团的相对含量(A_C=O/A_C-O=1.07)及较高的结构缺陷水平（I_D/I_G=1.14）。然而相对于N-BC,BC则表现出更高的持久性自由基（PFRs）含量。其中,BC700具有最高PFRs含量;（2）氮掺杂成功提高了BC的催化性能,在N-BC900投加量为0.10 g/L,PDS投加量1.00 m M,TCH初始浓度20.00 mg/L条件下,40 min内N-BC900/PDS体系对TCH去除效率达98.77%。且TCH的降解过程符合一级反应动力学,反应速率常数(k_obs)为0.0989 min^-1,相比原始生物炭中效果最佳的BC700/PDS体系提高了34倍;（3）N-BC900具有优异催化性能是由于其巨大的比表面积和高石墨化程度促进了对TCH的吸附,进而提高了对TCH的降解效果。N-BC表面的结构缺陷、C=O基团、吡啶N、石墨N作为活性位点在TCH降解过程中发挥了重要作用。而BC由表面PFRs作为主要活性位点实现对TCH的降解;（4）N-BC/PDS体系降解TCH主要为非自由基机制。其中,O₂·^-/¹O₂作为主导活性氧物质降解TCH。同时也存在以N-BC为介导,从TCH向PDS的电子转移途径。而BC/PDS体系则为·OH/SO₄·^-主导的自由基机制。上述分析表明氮掺杂诱导了生物炭活化PDS由自由基机制主导向非自由基机制主导的转变;（5）由于N-BC/PDS体系为非自由基机制主导,其在初始p H为3-7时均具有优异的降解性能,且在不同阴离子（Cl^-、NO₃^-、HCO₃^-）的存在或不同的水基质（自来水、天然水）中仍能保持90%以上TCH去除效率,表明该体系对水体中NOMs具有较强的抗干扰能力。更多还原

【Abstract】 As the most widely used antibiotics in our country,tetracycline antibiotics have been frequently detected in water effluents,which has aroused emerging concerns due to their seriously hazardous to the environment.The advanced oxidation process based on persulfate（SR-AOPs）is one of the effective strategies for removing tetracycline pollutants from water.Biochar,which is environment-friendly and has abundant pore structures,holds great promise for versatile applications in heterogeneous SR-AOPs.Biochar activates persulfate to degrade tetracycline,including radical and non-radical pathways,wherein the non-radical pathway is relatively mild and resistant to anions and background natural organic matter（NOMs）.Studies have found that the catalytic activity of most pristine biochar is unsatisfactory.In this regard,nitrogen doping has been found to effectively promote the catalytic activation of persulfate by biochar.However,the structures that play a significant role in enhancing persulfate activation by nitrogen-doped biochar and its mechanism remain ambiguous,which limits the directional design of nitrogen-doped biochar.In this study,tetracycline hydrochloride（TCH）was adopted as the target pollutant,corn stalk powder as raw material,and melamine as nitrogen precursor to prepare a series of pristine biochar（BC）and nitrogen-doped biochar（N-BC）at different pyrolysis temperatures to explore the effect of biochar structure on its peroxydisulfate（PDS）activation performance.In addition,electronic paramagnetic resonance（EPR）,quenching experiments,electrochemical analysis techniques,and high-performance liquid chromatography-mass spectrometry（LC-MS）were used to analyze the mechanism of PDS activation by BC or N-BC,providing a theoretical basis for the directional design of nitrogen-doped biochar.The main results of this study are as follows:（1）Nitrogen doping significantly changed the physical and chemical properties of biochar.N-BC prepared at 900℃（N-BC900）showed the highest specific surface area（1357 m²/g）,graphitization degree,and the relative amount of carbonyl groups(A_C=O/A_C-O=1.07).The defects level of N-BC900 was also increased（I_D/I_G=1.14）.Notably,BC showed a higher content of persistent free radicals（PFRs）,in which BC700 had the highest content of PFRs.（2）Nitrogen doping successfully improved the catalytic performance of BC.Under the conditions that the N-BC900 dosage was 0.10 g/L,the PDS dosage was 1.00m M,and the initial TCH concentration was 20.00 mg/L,the TCH removal efficiency of N-BC900/PDS system reached 98.77%within 40 min.The TCH degradation followed the first-order kinetics model with the reaction rate constant(k_obs)of 0.0989min^-1,which is 34 times higher than the optimal BC700/PDS system for the pristine biochar.（3）The excellent catalytic performance of N-BC900 is due to its huge specific surface area and high graphitization degree,which facilitates TCH adsorption,and thus improving the TCH degradation effect.Meanwhile,the defects,C=O groups,pyridine N and graphite N as active sites play an important role in TCH degradation.While PFRs on the BC surface act as the dominant active site to achieve TCH degradation.（4）The degradation of TCH by the N-BC/PDS system is mainly through the non-radical mechanism.Among,O₂·^-/¹O₂ act as the dominant reactive oxygen species.There is also an electron transfer pathway from TCH to PDS mediated by N-BC.In contrast,TCH degradation by BC/PDS system is a radical mechanism dominated by·OH/SO₄·^-.The above analysis indicated that nitrogen doping induced the transformation of biochar-activated PDS from a free radical mechanism to a non-free radical mechanism.（5）Owing to the non-radical dominant mechanism of the N-BC/PDS system,it exhibits excellent degradation performance at the initial p H of 3-7 and can still maintain over 90%TCH removal efficiency in the presence of different anions（Cl^-,NO₃^-,HCO₃^-）or different water substrates（tap water,natural water）,suggesting that the system has a strong anti-interference ability to NOMs in water.更多还原