石莼和龙须菜对染料亚甲基蓝的吸附研究

Biosorption of methylene blue by the macroalga:Ulva lactuca and Gracilaria lemaneiformis

为探讨大型海藻石莼(Ulva lactuca)和龙须菜(Gracilaria lemaneiformis)对染料亚甲基蓝(methylene blue)的吸附特性,文章通过静态吸附实验研究了溶液起始pH值、吸附时间、海藻生物量和染料浓度对海藻吸附亚甲基蓝的影响,并结合吸附等温线、吸附动力学、吸附热力学和红外光谱研究了其吸附机理.结果表明,石莼和龙须菜对亚甲基蓝的吸附容量随溶液起始pH值的增加而增加,最适pH值为4~10;60 min吸附达到平衡;吸附容量随着海藻生物量的增加而减少,但随着染料浓度的增加而增加.通过Langmuir和Freundlich等温吸附模型对数据进行拟合,Langmuir等温吸附模型能很好描述石莼和龙须菜对亚甲基蓝的吸附,拟合得出的最大吸附容量分别为709.22 mg·g^(-1)和231.48 mg·g^(-1).准二级动力学模型能很好描述反应的吸附动力学.吸附热力学分析显示石莼和龙须菜的吸附反应均为自发的放热反应.此外,吸附前后红外光谱结果说明在海藻表面的羟基、氨基和酰胺基与亚甲基蓝的吸附有关.结果表明,石莼和龙须菜对亚甲基蓝的吸附具有较高的吸附容量,是有潜力的染料废水吸附剂.

The adsorption characteristics of marine macroalga Viva lactuca and Gracilaria lemaneiformis for methylene blue from aqueous solution were investigated using a batch system. Adsorption mechanism was stud-ied by adsorption isotherm kinetic, thermodynamics and Fourier transform infrared spectroscopy. The result showed that adsorption capacity of Viva lactuca and Gracilaria lemaneiformis increased with the increase of initial pH value and the optimum pH was observed at 4 ？10. The adsorption achieved equilibrium within 60 min. The adsorption capacity increased with increasing methylene blue concentration. Langmuir model depicted the data better than Freundlich model. The maximum adsorption capacity of Viva lactuca and Gracilaria lemaneiformis obtained from Langmuir adsorption isotherm reached to 709. 22 mg·g^-1 and 231. 48 mg·g^-1 respectively. The pseudo second-order kinetic model could be used as a successful model to describe the biosorption kinetics. The adsorption process were spontaneous and exothermic for two biosorbents from adsorption thermodynamics. In ad-dition, FT-IR revealed that the algal surface possessed many functional groups such as hydroxyl, amino and acylamide involved in adsorption of methylene blue. It can be concluded that Viva lactuca and Gracilaria lema-neiformis are potential biosorbent for removing methylene blue.