洁净煤技术

2020, v.26;No.128(04) 196-202

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有机/无机酸改性兰炭基活性炭及其对焦化废水的吸附研究
Adsorption research on blue coke-activated carbon modified by organic acid/inorganic acid on coking wastewater

辛莹娟;蒋绪;张昭;冯伟帅;
XIN Yingjuan;JIANG Xu;ZHANG Zhao;FENG Weishuai;Research Institute of Energy and Chemical Industry,Xianyang Vocational Technical College;School of Metallurgical Engineering,Xi'an University of Architecture and Technology;

摘要(Abstract):

兰炭因其固定碳和化学活性高,且保留了低变质煤丰富的微孔结构,是一种优质且廉价的活性炭原料。但兰炭末制成的兰炭基活性炭具有孔径分布无序、表面化学性质局限等缺点,限制了其应用效果,而化学法改性可以弥补这一不足。笔者研究对比了无机酸和有机酸改性对兰炭基活性炭孔隙结构和表面化学性质的影响。常温下,分别用硝酸、磷酸、草酸和乙酸溶液对水蒸气活化制备的兰炭基活性炭进行改性,采用碘吸附试验、N2吸附/脱附试验、扫描电子显微镜和Boehm滴定等方法考察改性过程对活性炭孔隙结构和表面化学性质的影响,并对焦化废水进行吸附,分别研究了吸附剂投加量、吸附时间和转速对吸附效果的影响,用Langmuir和Freundlich模型模拟等温吸附过程。结果表明:改性后的兰炭基活性炭表面亲和力大的活性点由于受到酸的刻蚀发生了扩孔作用,导致其碘吸附值、比表面积和孔结构参数均降低,又因为活性炭边缘的高活性碳原子遇酸氧化后会结合氧原子形成含氧官能团,故表面含氧官能团含量升高,且氧化性越强的酸,结合的氧原子越多,硝酸改性后含氧官能团升高最明显,含量是改性前的2.41倍。焦化废水吸附试验表明,经酸改性后的兰炭基活性炭对焦化废水的吸附效果明显优于改性前,其中无机酸改性较有机酸更好,硝酸改性效果最佳,COD去除率比改性前最多可提升31.34%。这是因为焦化废水中污染物的主要是有较大分子量和分子直径的有机污染物,而酸改性使兰炭基活性炭平均孔径增加,中大孔比例提升,这有利于大分子有机污染物被吸附,而且改性后活性炭表面所增加的含氧官能团也提高了对污染物的亲水性和对极性有机物的亲和力。等温吸附试验表明,318 K条件下,50 m L焦化废水中加入4 g硝酸改性兰炭基活性炭吸附90 min后,COD去除率可达86.79%,吸附过程符合Langmuir模型。
Blue coke is a kind of high-quality and cheap raw material for activated carbon( AC) production because of its high fixed-carbon content,chemical activity,as well as the rich microporous structure of low metamorphic coal.However,the properties of AC prepared by blue coke powder,such as pore structure irregularity,low surface area,disordered pore size distribution,and limited surface chemical properties,limit its application effect,which can be made up by chemical modification.In this paper,the affection of blue coke-activated carbon( BAC) modified by organic acid inorganic acid on the pore structure and the surface chemical properties was investigated. The BAC was modified by nitric acid,phosphoric acid,oxalic acid and acetic acid respectively. By using iodine adsorbed,cryogenic N2 adsorption techniques,scanning electron microscopy( SEM),and Boehm titration,the properties of BAC were studied,and the adsorption of coking wastewater was carried out.The effects of modification on the adsorption behaviors of coking wastewater onto BACs at different temperatures and amount were researched,and the adsorption isotherms experiment has been studied by Langmuir model and Freundlich model.The results show that the active point with high affinity on the surface of the modified activated carbon is enlarged due to the etching of acid,resulting in the decrease of the iodine adsorption value,specific surface area and pore structure parameter.,And because the high active carbon atoms on the edge of activated carbon will combine with oxygen atoms to form oxygen-containing functional groups after being oxidized by acid,the content of oxygen-containing functional groups on the surface will increase,and the stronger the oxidizing acid is,the more oxygen atoms are,and the oxygen-containing functional groups will increase most obviously after nitric acid modification,and the number is2.41 times as many as unmodified. The adsorption test of coking wastewater shows that the adsorption effect of the acid modified activated carbon on coking wastewater is obviously better than that before modification,among which the inorganic acid is better than the organic acid,and the best adsorption effect can be obtained when the nitric acid modification and the COD removal rate increase to 31. 34%at most.This is because the pollutants in coking wastewater are mainly organic pollutants with large molecular weight and molecular diameter,and the acid modification makes the average pore diameter of the activated carbon based on Lancan increase,and the proportion of the medium and large pore increase,which is conducive to the adsorption of the organic pollutants,and the oxygen-containing functional groups added on the surface of the modified activated carbon also improve the hydrophilicity of the pollutants and the affinity to polar organic matters.The isothermal adsorption test shows that when 4 g BAC-N is added into 50 m L coking wastewater in 90 min at 318 K,the COD removal efficiency reaches to 86.79%,and the adsorption process is in accordance with Langmuir model.

关键词(KeyWords): 有机酸;无机酸;兰炭基活性炭;改性;焦化废水
organic acid;inorganic acid;blue coke-activated carbon;modification;coking wastewater

Abstract:

Keywords:

基金项目(Foundation): 陕西省教育厅专项资助项目(20JK0980);; 咸阳市科学技术研究攻关计划项目(2018K02-19)

作者(Author): 辛莹娟;蒋绪;张昭;冯伟帅;
XIN Yingjuan;JIANG Xu;ZHANG Zhao;FENG Weishuai;Research Institute of Energy and Chemical Industry,Xianyang Vocational Technical College;School of Metallurgical Engineering,Xi'an University of Architecture and Technology;

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DOI: 10.13226/j.issn.1006-6772.19120201

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