生物炭对土壤中四环素类抗生素的有效性和形态转化的影响

发布时间：2018-10-22 07:39

【摘要】：随着养殖业和医药业的迅猛发展,进入环境中的抗生素日益增多,四环素类抗生素(Tetracyclines)就是其中主要的一类抗生素。研究表明,土壤中残留的四环素类抗生素可通过食物链传输并累积风险,给人类健康和环境带来严重的威胁。因生物炭具有经济、安全以及高效等优点,近年来被广泛关注,利用生物炭增强土壤对四环素类抗生素的吸附等研究已取得诸多进展,但生物炭对四环素类抗生素有效性的影响和老化过程中四环素类抗生素各形态之间的转化等关键问题仍不明确,亟待研究探讨。本文研究了改性核桃壳基生物炭的制备及其对土霉素(Oxytetracycline)、四环素(Tetracycline)和金霉素(Chlortetracycline)为代表的四环素类抗生素的吸附性能;向土壤添加生物炭,探究生物炭对土壤吸附四环素类抗生素的强化作用及生物炭对四环素类抗生素有效性影响;进行土壤老化实验,探讨生物炭对四环素类抗生素在老化过程中形态转化的影响。取得的主要成果如下:(1)以系列浓度的KOH、H3PO4、ZnCl2为改性剂,核桃壳为原料制备核桃壳基生物炭,并对其进行表征,选择吸附性能较好的一种生物炭用于四环素类抗生素的吸附。结果表明:当四环素类抗生素初始浓度均为20 mg·L-1、生物炭用量为0.010 g时,反应24 h后基本达到平衡,土霉素、四环素和金霉素的吸附率分别为97.56%、91.14%和96.01%,吸附作用强弱顺序为土霉素金霉素四环素。该吸附动力学服从准二级动力学方程,吸附平衡类型与Langmuir等温吸附模型相似,且从热力学数据可以确定此吸附为放热反应。(2)添加生物炭能够增强黄棕壤对四环素类抗生素的吸附。对于吸附动力学实验,当土样均为1.00 g时,含1%生物炭的实验组的吸附速率远比不含生物炭的对照组要快;吸附平衡时,实验组的平衡吸附量分别为对照组的1.18、1.14和1.15倍,吸附能力强弱顺序为:土霉素金霉素四环素。反应均属于准二级动力学方程,吸附平衡类型接近Langmuir等温吸附方程,回归系数R2均大于0.99,并且添加生物炭能够大大提高对四环素类抗生素的吸附,降低有效性。(3)当含炭量为1%的黄棕壤中土霉素浓度分别为10、20、50 mg·kg-1时,随着老化时间的增加,部分可脱附态逐渐转化为结合态,并且随着土霉素初始浓度的增大,转化为结合态的量逐渐增大,但其结合态占总土霉素含量的比例却逐渐减小。生物炭含量分别为0%、1%和2%时,随着生物炭含量的增加,土样对土霉素的吸附能力增强,一定程度上能减少被吸附土霉素的脱附,也能降低土霉素的可提取态含量,减小其有效性。对于土霉素、四环素和金霉素这3种四环素类抗生素,可提取态转化为结合态的转化率大小顺序为:金霉素土霉素四环素。
[Abstract]:With the rapid development of aquaculture and medicine industry, the number of antibiotics entering the environment is increasing day by day. Tetracycline antibiotic (Tetracyclines) is one of the main antibiotics. Studies have shown that tetracycline antibiotics in soil can be transported through the food chain and accumulate risks, which pose a serious threat to human health and the environment. Because biochar has the advantages of economy, safety and high efficiency, it has been paid more and more attention in recent years. The study of using biochar to enhance the adsorption of tetracycline antibiotics has made a lot of progress. However, the effects of biochar on the availability of tetracycline antibiotics and the transformation of tetracycline antibiotics in different forms during aging are still unclear. The preparation of modified walnut shell based biochar and its adsorption on tetracycline antibiotics represented by oxytetracycline (Oxytetracycline),) tetracycline (Tetracycline) and chlortetracycline (Chlortetracycline) were studied. To explore the enhancement effect of biochar on the adsorption of tetracycline antibiotics and the effect of biochar on the availability of tetracycline antibiotics, and to investigate the effect of biochar on the morphological transformation of tetracycline antibiotics during aging. The main results are as follows: (1) A series of KOH,H3PO4,ZnCl2 was used as modifier and walnut shell was used as raw material to prepare walnut shell based biochar, which was characterized and used to adsorb tetracycline antibiotics. The results showed that when the initial concentration of tetracycline antibiotics was 20 mg L ~ (-1) and the amount of biochar was 0.010 g, the equilibrium of tetracycline antibiotics was basically achieved after 24 h reaction. The adsorption rates of tetracycline and chlortetracycline were 97.56% and 96.01% respectively. The order of adsorption was oxytetracycline. The adsorption kinetics was derived from the quasi-second-order kinetic equation, and the adsorption equilibrium type was similar to that of the Langmuir isothermal adsorption model. The thermodynamic data showed that the adsorption was an exothermic reaction. (2) addition of biochar could enhance the adsorption of tetracycline antibiotics in yellow brown soil. For adsorption kinetics experiment, when soil sample is 1.00 g, the adsorption rate of experimental group containing 1% biochar is much faster than that of control group without biochar, and the equilibrium adsorption capacity of experimental group is 1.18 ~ 1.14 and 1.15 times of that of control group respectively. The order of adsorption ability was: tetracycline oxytetracycline. The adsorption equilibrium type is close to the Langmuir isotherm adsorption equation, and the regression coefficient R2 is greater than 0.99, and the adsorption of tetracycline antibiotics can be greatly improved by adding biochar. (3) when the concentration of oxytetracycline in yellow brown soil with 1% carbon content was 10 ~ 20 ~ 50 mg kg-1, with the aging time increasing, part of the desorption state was gradually transformed into a bound state, and the initial concentration of oxytetracycline increased with the increase of the initial concentration of oxytetracycline. The amount of conversion to binding state increased gradually, but the ratio of bound state to total oxytetracycline content decreased gradually. When the content of biochar was 0% and 2%, the adsorption ability of oxytetracycline was enhanced with the increase of biochar content, which could reduce the desorption of oxytetracycline and the extractable content of oxytetracycline to some extent. Reduce its effectiveness. For three tetracycline antibiotics, oxytetracycline, tetracycline and chlortetracycline, the order of conversion of extractable state to bound state is as follows: chlortetracycline tetracycline.
【学位授予单位】：南京农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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