氢氧化镁对水中As(Ⅲ)的吸附作用
Adsorption of As (Ⅲ) ions from aqueous solution by magnesium hydroxide
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摘要: 以氢氧化镁为吸附材料，通过单因素实验分别考察了氢氧化镁投加量、pH 、温度、吸附时间对吸附效果的影响。研究了氢氧化镁对As(Ⅲ)的吸附热力学和动力学特性，并对作用机理进行了探讨。结果表明：在砷初始浓度为0.5～100 mg/L之间，温度为25℃，pH为3，氢氧化镁投加量为0.5～4 g，吸附时间为1 h的条件下，氢氧化镁对砷离子的去除率可以达到99%以上。在相同条件下，氢氧化镁对水中As(Ⅲ)的吸附平衡时间是80 min。吸附等温线符合Freundlich模型，双常数模型和抛物线动力学方程较好地表征了氢氧化镁吸附As(Ⅲ)的动力学特性。吸附自由能△Go为负值，表明氢氧化镁吸附As(Ⅲ)的过程是自发的。Abstract: With magnesium hydroxide as the absorbent， the effects of magnesium hydroxide dose，pH，temperature，time on the adsorption were investigated. The adsorption equilibrium， kinetics and thermodynamics of As(Ⅲ) ions onto magnesium hydroxide were studied， the reaction mechanism was discussed. The results showed that while the initial arsenic concentration is 0.5～100 mg/L ，temperature is 25℃， pH is 3， magnesium hydroxide dosage is 0.5～4 g， adsorption time is 1 h， the adsorption rate reaches more than 99%. Under the same conditions， the adsorption equilibrium time is 80 min. The adsorption isotherm accords with Freundlich mode. The double-constant rate equation and the parabolic diffusion kinetic equation can express the dynamics characteristics well. The adsorption free energy △Go is a negative value， which indicates that the process of adsorption As(Ⅲ) onto magnesium hydroxide is spontaneous.
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Key words:
- magnesium hydroxid /
- As(Ⅲ) /
- adsorption /
- thermodynamics /
- kinetics
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