王棕果壳粉吸附亚甲基蓝性能研究

摘要

研究了不同条件下王棕果壳粉对亚甲基蓝的吸附性能,得到吸附的最佳条件为王棕果壳用量10 g/L,溶液pH值7,吸附时间30 min,温度30℃,亚甲基蓝去除率可达98%。应用准一级动力学方程、准二级动力学方程、颗粒内扩散方程模拟了王棕果壳粉吸附亚甲基蓝的动力学过程,准二级动力学方程的R2值均大于0.9991,且平衡吸附量的计算值( qe,cal )与实验值( qe,exp )非常接近,说明该方程适合描述整个吸附过程。用Langmuir和Freundlich模型模拟吸附等温线,结果表明Langmuir方程(R2值均大于0.995)更适合描述此吸附过程,在303 K下最大单层吸附量为17.36 mg/g。计算了吉布斯自由能变(ΔG0)、焓变(ΔH0)、熵变(ΔS0)、吸附势( E)等热力学参数,ΔG0、ΔH0、ΔS0均小于0,说明此吸附过程是一个自发进行的、放热的、趋于有序的吸附过程。在相同温度下,随着亚甲基蓝初始质量浓度的增加,对应的E值逐渐降低。%The adsorption properties of Roystonea regia shell for methylene blue at different conditions were studied. The optimal adsorption conditions were the dosage of Roystonea regia shell 10 g/L, PH value 7, adsorption time 30 min and temperature 30℃. At this condition, the removal rate of MB was about 96. 11%. The pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to fit adsorption data in the kinetic studies. And the results showed that the adsorption kinetic described by the pseudo-second-order model was more accurate with R2>0. 999 1 and values of qe.cal and qe.exp were close . The equilibrium isotherms were conducted by using Langmuir and Freundlich models. The adsorption could be well depicted by the Langmuir adsorption isotherm(R2>0.995). And the maximum monolayer adsorption capacity was 17.36 mg/g at 303K estimated from the Langmuir model. The Gibbs free energy change(ΔG0 ) , enthalpy change (ΔH0 ) , entropy change (ΔS0 ) and adsorption potential( E) were calculated. The ΔG0 , ΔH0 and ΔS0 were negative. This indicated that the adsorption was a spontaneous, exothermic and decreasing entropy process. At the same temperature, with the increase of concentration of methylene blue solution, the adsorption potential gradually reduced.