粉末活性炭对偶氮染料的吸附特性及作用机制

来源期刊:中南大学学报(自然科学版)2019年第12期

论文作者:周志伟 张婷婷 杨艳玲 李星 姜伊凡 王男 冀思扬

文章页码:2938 - 2948

关键词:粉末活性炭;偶氮染料;吸附特性;吸附动力学;吸附等温线

Key words:powdered activated carbon; azo dyes; adsorption characteristic; kinetics; isotherms

摘    要:研究不同种类粉末活性炭(PAC)对2种偶氮类染料(直接耐晒桃红BK和活性橙X-GN)的吸附特性和影响因素,表征3种不同材质PAC的理化特性,分析PAC对典型偶氮类染料的吸附动力学、吸附等温线及作用机制。研究结果表明:对偶氮染料吸附效果最佳的PAC具有比表面积最大、烧结现象少、以中孔和大孔结构为主、表面氧元素含量高并以C=O,—OH和—COOH等酸性官能团为主等特点。偶氮染料的吸附是不均匀吸附,包括表面吸附、外部液膜扩散和颗粒内扩散;偶氮染料分子主要吸附于PAC的中孔(大孔)中,初始阶段为快速吸附,后期以扩散作用为主导,吸附动力学均符合拟二级动力学模型,吸附等温线符合修正的Freundlich方程。偶氮染料在PAC上的吸附机制主要以化学吸附作用为主,表现为PAC表面官能团与染料分子之间的氢键作用以及两者之间的范德华力和静电作用。

Abstract: The adsorption characteristics and influencing factors of two azo dyes(direct sunlight-resistant peach red-BK and reactive brilliant orange X-GN) on different kinds of powdered activated carbon (PAC) were studied. The physical and chemical properties of the three PACs were characterized. The adsorption kinetics, isotherm and mechanism involved of PAC on typical azo dyes were analyzed. The results indicate that the best adsorption effect of azo dyes can be obtained with the largest BET-specific surface area and less surface sintering and the highest number of mesoporous and macro-porous of PAC, which is high in oxygen elements and mainly consists of acidic functional groups such as C=O, —OH and —COOH. The adsorption of azo dyes onto PAC is inhomogeneous, including surface adsorption, external liquid membrane diffusion and intra-particle diffusion as well. Azo dye molecules are mainly adsorbed in the mesoporous (macro-porous) of PAC, and the initial stage is dominated by rapid adsorption followed by diffusion in the later stage. The adsorption kinetics fit well with the pseudo-second-order kinetics model, and the adsorption isotherms follow amendatory Freundlich equation. The main mechanism of azo dyes adsorbed on PAC is mainly chemisorption and predominated by hydrogen bonding, Van der Waals interaction force, as well as electrostatic interaction of the functional groups between PAC surface and dye molecular.

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