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通过试验对粒径介于0.25～0.50 mm的花生壳颗粒吸附Cr(VI)的动力学行为进行探讨,从吸附时间、pH值、吸附剂投加量、温度、Cr(VI)的初始质量浓度方面对吸附性能的影响进行研究。结果表明,最佳吸附条件为:Cr(VI)初始质量浓度100 mg/L,pH=2.0,振荡速度140 r/min,温度30℃。此时Cr(VI)的吸附率可达到90%以上。用Lagergren一级吸附速率方程、二级吸附速率方程及平均绝对偏离率对以上因素对吸附性能的影响数据进行处理,发现二级吸附动力学模型可以更好地描述各种影响因素条件下的吸附过程。二级吸附速率常数随着溶液pH值和Cr(VI)初始质量浓度的减小而增大。在低浓度和低pH值的条件下,Cr(VI)主要以HCrO_4~-形式存在,并且HCrO_4~+是花生壳主要吸附的Cr(VI)。二级吸附速率常数随着溶液温度的升高而快速的增加。温度对反应速率的影响可以通过Arrhenius方程来描述,所得曲线近似为直线方程,决定系数R~2=0.986 2,反应的活化能E_a为8.67kJ/mol,该反应活化能在物理吸附反应活化能范围(0～40 kJ/mol)内。
The kinetic behavior of Cr (VI) adsorbed on peanut shell particles with particle size of 0.25-0.50 mm was studied through experiments. The adsorption kinetics of Cr (VI) from the adsorption time, pH, dosage of adsorbent, temperature, initial mass concentration of Cr The impact of adsorption properties were studied. The results showed that the optimal adsorption conditions were as follows: Cr (VI) initial concentration 100 mg / L, pH 2.0, shaking speed 140 r / min, temperature 30 ℃. At this point Cr (VI) adsorption rate can reach more than 90%. The effects of the above factors on the adsorption performance were analyzed by using the Lagergren first-order adsorption rate equation, the second-order adsorption rate equation and the average absolute deviation rate. The results showed that the second-order adsorption kinetics model can better describe the adsorption of various factors process. The second order adsorption rate constant increases with decreasing solution pH and Cr (VI) initial mass concentration. At low concentration and low pH, Cr (VI) mainly exists in the form of HCrO_4 ~ -, and HCrO_4 ~ + is the main adsorbed Cr (VI) in peanut shells. The second order adsorption rate constant increases rapidly with the increase of solution temperature. The effect of temperature on the reaction rate can be described by the Arrhenius equation. The obtained curve approximates to a straight line equation, and the coefficient of determination is R 2 = 0.986 2. The activation energy E_a of the reaction is 8.67 kJ / mol. Range (0 ~ 40 kJ / mol) within.