果壳类活性炭对纸浆漂白废水中AOX的吸附性能研究
发布时间：2018-12-19 09:38
【摘要】：可吸附有机卤化物(AOX)主要来源于制浆造纸漂白阶段,以二氧化氯为主的无元素氯(ECF)漂白技术虽然可以大幅度降低废水中AOX的含量,但是由于制浆造纸废水排放量大,AOX排放到自然环境中的总量在不断增加。AOX属于持久性有机污染物(POPs),具有长期残留性、生物蓄积性、高毒性和长距离迁移性,经自然降解后,含量减少甚微,对环境的危害越来越大。果壳类活性炭是一种孔隙发达、比表面积大、吸附能力强的功能型碳材料,被广泛应用于环保领域。本论文详细探究了无元素氯漂白废水中AOX的自然降解规律,以果壳类活性炭吸附漂白废水中的AOX,并对吸附条件进行工艺优化,建立活性炭吸附2,4,6-三氯苯酚(TCP)和1,2,4-三氯苯(TCB)的动力学模型,为监测实际环境中AOX污染物的分布提供理论依据。1.漂白废水经过45天自然降解后,AOX含量由25.98 mg.L~-1降低到21.97 mg.L~-1 通过气质联用(GC-MS)分析发现漂白废水自然降解后氯乙酸、氯丙酮等小分子物质含量有所降低,氯苯、氯苯酚等大分子有机氯化物含量变化不明显。2.利用XRD分析发现活性炭以非晶型结构为主,SEM观察发现其表面有丰富的孔隙结构。通过多站比表面积测试仪(BET)测得:活性炭比表面积为1241m2.g 1、平均孔径为2.21 nm,利用测试数据分析发现活性炭孔径主要集中在1-4nm,而且具有大量的微孔和中孔,属于Ⅳ型吸附等温线。3.通过单因素实验和响应面分析技术对AOX的吸附条件进行优化:活性炭的粒径为75 um,吸附时间为100 min,吸附温度50℃,活性炭的投加量为1.50 g.L~-1,废水pH值为2.47时,能达到的最大吸附量为4.385 mg.g~-1。利用GC-MS分析活性炭处理前后的漂白废水结果显示:经活性炭吸附后的漂白废水中,氯丙酮、2-氯-对苯二酚、二氯苯基酯、三氯苯、三氯苯酚均被大量去除。EDAX能谱显示:在吸附AOX后的活性炭上,氯元素由0.01%增加到2.32%。4.以2,4,6-TCP和1,2,4-TCB为AOX模拟物,利用吸附动力学模型和吸附等温模型对吸附实验数据进行拟合。其中,活性炭对2,4,6-TCP的吸附过程符合二级动力学模型和Freundlich等温模型,二级动力学模型和Langmuir等温吸附模型能够很好地描述活性炭对1,2,4-TCB的吸附过程。通过Dumwald-Wagner公式对吸附机理进探讨发现,吸附过程除了颗粒内扩散外还有其他控制步骤。吸附热力学实验结果证明两者的吸附过程均属于放热反应。
[Abstract]:Adsorbable organic halide (AOX) mainly comes from pulping and papermaking bleaching stage. Although chlorine dioxide based non-elemental chlorine (ECF) bleaching technology can greatly reduce the content of AOX in wastewater, the discharge of pulp and papermaking wastewater is large. The total amount of AOX released into the natural environment is increasing. AOX is a persistent organic pollutant, (POPs), has long-term residual, bioaccumulation, high toxicity and long distance migration. After natural degradation, the content of AOX decreases very little. The damage to the environment is getting bigger and bigger. Shell activated carbon is a kind of functional carbon material with developed pores, large specific surface area and strong adsorption ability, which is widely used in environmental protection field. In this paper, the natural degradation law of AOX in elemental chlorine bleaching wastewater was studied in detail. The adsorption conditions of AOX, in bleaching wastewater were optimized with shell activated carbon, and the adsorption conditions were optimized to establish the adsorption of 2N 4N 6 trichlorophenol (TCP) and 1 trichlorophenol by activated carbon. The kinetic model of 4-trichlorobenzene (TCB) provides a theoretical basis for monitoring the distribution of AOX pollutants in real environment. 1. After 45 days of natural degradation of bleaching wastewater, the content of AOX was reduced from 25.98 mg.L~-1 to 21.97 mg.L~-1. The results of GC-MS analysis showed that chloroacetic acid was degraded naturally from bleaching wastewater. The content of small molecular substances such as chloroacetone decreased, while the content of macromolecular organic chlorides such as chlorophenol did not change obviously. 2. The amorphous structure of activated carbon was found by XRD analysis, and the pore structure on the surface of activated carbon was found by SEM. The specific surface area of activated carbon is 1241m2.g 1, and the average pore size is 2.21 nm,. By analyzing the measured data, it is found that the pore size of activated carbon is mainly concentrated in 1-4 nm, and has a large number of micropores and mesoporous pores. It belongs to type 鈪，
本文编号：2386741
[Abstract]:Adsorbable organic halide (AOX) mainly comes from pulping and papermaking bleaching stage. Although chlorine dioxide based non-elemental chlorine (ECF) bleaching technology can greatly reduce the content of AOX in wastewater, the discharge of pulp and papermaking wastewater is large. The total amount of AOX released into the natural environment is increasing. AOX is a persistent organic pollutant, (POPs), has long-term residual, bioaccumulation, high toxicity and long distance migration. After natural degradation, the content of AOX decreases very little. The damage to the environment is getting bigger and bigger. Shell activated carbon is a kind of functional carbon material with developed pores, large specific surface area and strong adsorption ability, which is widely used in environmental protection field. In this paper, the natural degradation law of AOX in elemental chlorine bleaching wastewater was studied in detail. The adsorption conditions of AOX, in bleaching wastewater were optimized with shell activated carbon, and the adsorption conditions were optimized to establish the adsorption of 2N 4N 6 trichlorophenol (TCP) and 1 trichlorophenol by activated carbon. The kinetic model of 4-trichlorobenzene (TCB) provides a theoretical basis for monitoring the distribution of AOX pollutants in real environment. 1. After 45 days of natural degradation of bleaching wastewater, the content of AOX was reduced from 25.98 mg.L~-1 to 21.97 mg.L~-1. The results of GC-MS analysis showed that chloroacetic acid was degraded naturally from bleaching wastewater. The content of small molecular substances such as chloroacetone decreased, while the content of macromolecular organic chlorides such as chlorophenol did not change obviously. 2. The amorphous structure of activated carbon was found by XRD analysis, and the pore structure on the surface of activated carbon was found by SEM. The specific surface area of activated carbon is 1241m2.g 1, and the average pore size is 2.21 nm,. By analyzing the measured data, it is found that the pore size of activated carbon is mainly concentrated in 1-4 nm, and has a large number of micropores and mesoporous pores. It belongs to type 鈪，
本文编号：2386741
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