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随着全球医疗技术的发展和抗生素的广泛使用,医疗废水尤其是抗生素废水对人类和生态环境造成了严重的危害[1]。四环素作为世界上应用比较广泛的一类抗生素,主要用来治疗各种人类和动物疾病,然而研究表明,动物不能完全吸收和代谢摄入的抗生素,大部分抗生素则是以粪便的形式排放到环境中,四环素在环境中的积累会对土壤和自然水体造成污染,从而对人类的健康构成潜在威胁[2-4]。
目前有很多方法被应用在四环素的去除方面,包括吸附法、生物降解法、光降解法和氧化降解法等[5-8]。其中吸附法由于其操作简单、成本低、效率高和无副产物残留风险等优点得到了研究者的广泛关注[9-10]。在众多吸附材料中,碳材料凭借制备简单、吸附效果好和绿色环保等优点在吸附材料方面更占优势,常见的碳材料分为活性炭、石墨烯、生物炭和一些有机复合材料[11-12]。
海藻酸钠是一种能直接从褐藻中提取的天然生物大分子,无毒无害而且具有很好的生物相容性[13-14]。研究表明,海藻酸钠可以与多种金属离子发生凝胶反应,包括Mg2+、Ca2+、Ba2+、Co2+、Cu2+、Ni2+和Fe2+等[15-17]。燃煤电厂脱硫废水是工业水处理中比较难处理的一类水体,具有成分复杂、含盐量高、重金属污染物浓度高和腐蚀性强等特点,海藻酸钠可以有效利用脱硫废水中的重金属污染物作为交联剂原位实现海藻酸钠的凝胶化[18-20]。本研究采用与脱硫废水中重金属污染物络合形成的海藻酸钠水凝胶,通过碳化的方式来制备海藻酸钠基多孔碳气凝胶,在实现脱硫废水深度处理的同时有效利用处理完脱硫废水的凝胶废弃物。利用SEM、XRD、FTIR和BET等表征手段研究了海藻酸钠基多孔碳气凝胶的结构特征,通过一系列实验考察了在不同pH和反应时间的条件下海藻酸钠基多孔碳气凝胶对溶液中四环素的吸附效果,并对吸附动力学和吸附等温线进行了数据分析,最后通过结构特征和吸附效果来探究海藻酸钠基多孔碳气凝胶对水中抗生素的去除机理。
海藻酸钠基多孔碳气凝胶的制备及其对水中四环素去除
Preparation of sodium alginate-based porous carbon aerogel and its removal of tetracycline from aqueous solution
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摘要: 采用脱硫废水中的重金属污染物原位交联使海藻酸钠形成水凝胶,再将该水凝胶在800 ℃的条件下制备为海藻酸钠基多孔碳气凝胶,利用场发射扫描电子显微镜(SEM)、比表面积分析仪、X射线衍射(XRD)和傅里叶红外光谱(FTIR)对该气凝胶进行了表征分析,并考察了该气凝胶对溶液中四环素的吸附行为。结果表明,该碳气凝胶具有丰富的孔隙结构,比表面积可以达到52.37 m2/g。 随着溶液初始pH值的增大,碳气凝胶对四环素的吸附量逐渐降低。碳气凝胶对四环素的吸附行为更符合准二级动力学方程(R2=0.825 7),最大吸附量可以达到112 mg/g,等温吸附过程对Freundlich 等温吸附模型比对Langmuir等温吸附模型拟合度更高,说明利用处理脱硫废水的凝胶废弃物制备的海藻酸钠基多孔碳气凝胶在去除水环境中的抗生素方面有较好的应用前景,实现了脱硫废水凝胶废弃物的资源化利用。Abstract: Sodium alginate hydrogel was formed by in situ cross-linking of heavy metal pollutants in desulfurization wastewater, and sodium alginate-based porous carbon aerogel was prepared at 800 ℃. Then the removal effect of sodium alginate hydrogel on tetracycline in solution were studied. The carbon aerogel was characterized by scanning electron microscopy (SEM), accelerated surface area and porosimetry system, X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. The results showed that the sodium alginate-based carbon aerogel had a rich pore structure, and the specific surface area could reach 52.37 m2/g. With the increase of the initial pH of the solution, the adsorption capacity of tetracycline by the carbon aerogel gradually decreased. The adsorption kinetic of tetracycline onto sodium alginate-based porous carbon aerogel was fitted to pseudo-second-order models (R2=0.825 7). The maximum adsorption capacity could reach 112 mg/g. The adsorption isotherm process was more in line with the Freundlich isotherm adsorption model than the Langmuir model, thus indicating that the sodium alginate-based porous carbon aerogel prepared by the gel waste of desulfurization wastewater had a good application prospect in removing antibiotics in the water environment. The desulfurization wastewater gel waste could be recycled as the resource.
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Key words:
- desulfurization wastewater /
- sodium alginate /
- carbon aerogel /
- tetracycline /
- adsorption /
- resource utilization
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表 1 吸附前后海藻酸钠基多孔碳气凝胶元素组成
% 元素种类 吸附前凝胶 吸附后凝胶 C 11.60 22.70 Mg 16.67 9.30 Cl 13.86 0.57 Ca 11.43 0.88 O 46.44 66.55 表 2 海藻酸钠基多孔碳气凝胶的吸附动力学参数
项目 准一级动力学模型 准二级动力学模型 qe/mg·g−1 0.8590 0.9690 k/min−1 0.0150 0.0210 R2 0.7218 0.8257 表 3 海藻酸钠基多孔碳气凝胶对四环素的吸附等温线参数
项目 Langmuir模型 Freundlich模型 KL/mg·L−1 0.0886 − KF/(mg1·1/n·L1/n)·g−1 − 9.5860 qm/mg·g−1 112 − 1/n − 0.5229 R2 0.9130 0.9798 -
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