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抗生素在使用过程中由于无法被完全代谢排入水中体,这会对生态环境造成严重破坏[1-3]。目前,抗生素废水的处理方法主要有混凝法、生物法、化学氧化法、膜分离法等[4-5]。吸附法具有操作简单,适用范围广,能处理废水中低浓度的抗生素而受到广泛关注[6]。吸附剂是吸附技术的核心。HU等[7]制备了椰壳生物炭,其对左氧氟沙星和金霉素的吸附量分别为 397.7 mg·g−1和 320.9 mg·g−1。ZENG等[8]制备了活性百慕大草衍生的生物炭,对磺胺甲恶唑的吸附量为 425 mg·g−1。CHANG等[9]制备了累托石,其对金霉素的饱和吸附量为 140 mg·g−1。ZHANG等[10]制备了磁性铁矿纳米粒子,其对金霉素的饱和吸附量为 476.2 mg·g−1。AMALY等[11]制备的聚苯胺分层结构的纳米纤维吸附剂,对四环素的饱和吸附量为600 mg·g−1。LI等[12]制备的GO/TiO2 纳米复合材料,对金霉素的饱和吸附量为261.1 mg·g−1。在以上研究中,生物质炭价格低廉,但吸附性能较低,一些高分子复合材料吸附量能达到500 mg·g−1以上,但其价格较昂贵且制作工艺较为复杂。因此,需要研究一种制作工艺简单,原料来源广泛,价格低廉的吸附剂对水环境中的抗生素进行有效去除。
煤沥青是重油加工的副产品,含碳量较高,可以通过物理和化学方法将其转化为多孔碳,从而对其实现高附加值利用[13]。有研究[14]表明,煤沥青在高温下表现出一定的流动性,有助于利用模板剂和活化剂实现对其孔隙形状和结构的定向控制。由于这些优点,煤沥青基多孔材料可用于催化、电化学、生物医学、环保和军事等领域[15-16]。其中在环保领域,煤沥青基活性炭被广泛用于吸附染料、VOCs等污染物,但在吸附抗生素方面的研究鲜有报道,为此,本文以2-甲基咪唑为氮源,制备了煤沥青基掺N多孔炭,考察了其对金霉素的吸附性能[17],并使用SEM、BET、FTIR、XPS等分析方法对其物理结构和表面化学性质进行表征,且进一步阐述了可能的吸附机理。
煤沥青基掺N多孔炭的制备及其对金霉素的吸附性能
Preparation of coal tar-based N-doped porous carbon and its adsorption performance towards chlortetracycline
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摘要: 以煤沥青为碳源,2-甲基咪唑作为氮源,通过MgO模板耦合KOH活化一步制备得到具有高比表面积的掺N多孔炭(DCCx)。分别采用比表面积及孔径分析、扫描电子显微镜、X射线光电子能谱和傅立叶变换红外光谱仪等方法对DCCx进行了表征,并考察了其对废水中金霉素的吸附性能。结果表明,所制备的多孔炭具有层堆叠结构;制得的DCC2.0比表面积高达2 969 m2·g −1。红外光谱图中出现了明显的C=C、 C=N及硝基基团的吸收峰。DCC2.0中吡咯态氮和吡啶态氮的含量较高。DCC2.0对金霉素的饱和吸附容量高达 1 368 mg·g−1,且符合Langmuir吸附等温线模型;金霉素在多孔炭表面的吸附速度快,其符合拟二级动力学模型。Abstract: The high surface area N-doped porous carbon (DCCx) was prepared by MgO template coupled with KOH activation when coal tar and 2-methylimidazole were taken as carbon and nitrogen sources, respectively. The as-prepared DCCx was characterized by BET, SEM, XPS and FTIR, and its adsorption performance towards chlortetracycline (CTC) in wastewater was investigated. The results showed that DCCx had a type of obvious irregular layer bulk accumulation structure. The specific surface area of the obtained DCC2.0 was up to 2969 m2·g−1. The obviously tensile vibration of C=C bond C=N group appeared in FTIR spectra. DCC2.0 had a high content of pyrrole N and pyridine N. The saturated adsorption capacities of chlortetracycline on DCC2.0 was 1368 mg·g−1, the adsorption process fitted well with Langmuir isotherm model. The adsorption rate of chlortetracycline on porous carbons was fast, the kinetic adsorption process could be described by the pseudo-second-order kinetic model.
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Key words:
- adsorption /
- antibiotic /
- porous carbon /
- nitrogen doping
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表 1 DCCx 的比表面积及孔结构参数
Table 1. Specific surface area and pore structure parameters of DCCx
样本 比表面积/(m2·g−1) 微孔比表面积 /(m2·g−1) 总孔容/(mL·g−1) 微孔孔容/(mL·g−1) 平均孔径/nm DCC0.5 2 589 2 217 2.25 1.12 3.47 DCC2.0 2 969 2 400 2.52 1.21 3.40 DCC4.0 2 706 2 339 2.85 1.17 4.21 表 2 XPS元素含量表
Table 2. Element content determined by XPS analysis %
样本 C O N —C=O —CO —OH 氧化态 N 石墨化 N 吡咯态 N 吡啶态 N DCC0.5 88.22 9.88 1.90 0.21 0.46 0.33 0.37 0.09 0.47 0.07 DCC2.0 85.81 10.52 3.67 0.28 0.46 0.26 0.10 0.16 0.53 0.21 DCC4.0 90.23 6.17 3.61 0.13 0.67 0.20 0.18 0.14 0.57 0.11 表 3 DCCx吸附CTC的内扩散模型参数
Table 3. Parameters of the internal diffusion model for CTC adsorption on DCCx
样本 Kd1/
(mg·g−1·min1/2)C/
(mg·g−1)R2 Kd2 C R2 Kd3 C R2 DCC0.5 120.33 182 0.99 25.86 376 0.83 4.97 459 0.95 DCC2.0 113.20 257 0.99 19.14 424 0.81 1.19 490 0.80 DCC4.0 76.72 58 0.96 25.90 262 0.93 — — — 表 4 DCCx吸附CTC的拟一级、拟二级动力学模型参数
Table 4. Pseudo-first-order and pseudo-second-order kinetic model parameters for CTC adsorption on DCCx x
样本 拟一级动力学 拟二级动力学 qe/
(mg·g−1)K1/
(g·(mg·min)−1)R2 qe/
(mg·g−1)K2/
(g·(mg·min)−1)R2 DCC0.5 459 0.052 0.88 500 0.002 5 0.99 DCC2.0 475 0.079 0.72 500 0.007 6 0.99 DCC4.0 342 0.038 0.95 490 0.000 4 0.99 表 5 DCCx吸附CTC的Langmuir和Freundlich模型拟合参数
Table 5. Parameters of Langmuir and Freundlich model for CTC adsorption on DCCx
样本 Langmuir模型 Freundlich模型 qm/(mg·g−1) KL/( L·mg−1) R2 n KF/(mg1−n·g−1·L1/n) R2 DCC0.5 1 247 2.22 0.99 5.23 708.56 0.94 DCC2.0 1 368 1.40 0.99 5.48 646.19 0.64 DCC4.0 909 0.84 0.99 4.44 375.47 0.50 -
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