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摘要: 利用尿素溶液氨化改性小麦秸秆,通过扫描电镜和傅里叶变换红外光谱观察其改性前后的表征,研究不同初始pH与投加浓度对改性前后小麦秸秆吸附水溶液中Cd 2+的效果,并通过动力学与热力学模型拟合小麦秸秆的吸附动力学与等温吸附特征。结果表明:氨化改性小麦秸秆的结构疏松,孔隙增大,表面嫁接了伯酰胺基团,各官能团活性增强,有利于提高对Cd 2+的吸附能力;氨化改性小麦秸秆吸附Cd 2+的最适宜条件是pH为6、温度为25 ℃、吸附剂投加浓度为1/300 g/mL,此条件时对Cd 2+的吸附率达74.32%,最大饱和吸附量为11.29 mg/g;不同温度下,氨化改性小麦秸秆对Cd 2+的吸附可用准二级动力学方程描述,表现为吸热反应;对Cd 2+的吸附热力学过程可用Langmuir模型描述,表现为以化学吸附为主。Abstract: In order to solve the problem of chromium-contaminated wastewater, urea ammoniated modified wheat straw was prepared as a kind of Cd 2+ sorbent. The characterization before and after modification was observed by scanning electron and Fourier transform infrared spectroscopy, and the effects of different initial pH and dosage concentration on adsorption capacity of Cd 2+ by wheat straw before and after modification were studied. The adsorption kinetics and isothermal characteristics of wheat straw were fitted by kinetic and thermodynamic models. The results showed that the structure of the ammoniated wheat straw (N1) was loose, the pores were enlarged, the surface was grafted with primary amide group, and the activity of each functional group was enhanced, which was conducive to improving the adsorption capacity of Cd 2+. The optimum conditions for Cd 2+ adsorption on wheat straw after ammoniation modification were pH of 6, temperature of 25 ℃ and sorbent dosage of 1/300 g/mL. Under these conditions, the removal rate and the biggest saturated adsorption capacity were 74.32% and 11.29 mg/g, respectively. At different temperatures, the adsorption kinetics of Cd 2+ on wheat straw modified by ammonia could be described by the quasi-second order kinetic equation, which was shown as the endothermic reaction. The thermodynamic process could be described by Langmuir model, indicating that the adsorption on Cd 2+ was dominated by chemical adsorption.
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Key words:
- ammonification /
- modified wheat straw /
- Cd 2+ /
- adsorption property
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