Wang Peifang, Wu Chuangfei, Guo Yong, Wang Chao
Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, P. R. China.
Phys Chem Chem Phys. 2016 Nov 2;18(43):30196-30203. doi: 10.1039/c6cp04625h.
Wheat straw-derived biochar (BC-4-700) with a large surface area (2263.10 m g) has been synthesized using potassium hydroxide as an activating agent, and its sorption performance is evaluated by sorbing methylene blue (MB) and methyl orange (MO). The sorption behaviours of both MO and MB by BC-4-700 all follow pseudo-second-order and Langmuir models, and the driving forces for the two sorptions are attributed to the pi-pi interaction. The largest sorption quantity for MO by BC-4-700 is 3.24 mmol g, being 1.37 times larger than that for MB (2.36 mmol g). There is an inflection point in the isotherm sorption curve of MB. It is widely accepted that MB is a cationic dye and MO is an anionic dye. However, the two experimental phenomena cannot be explained well by the widely accepted MB form. The pH detection experiments on MB and MO solutions suggest that MO does not hydrolyze in water and the existing form in water is the well-accepted MO, whereas MB hydrolyzes in water and the existing forms in water most likely include both the well-accepted MB and the hydrolyzed form of MB. This finding can account well for the two experimental phenomena mentioned above, which is helpful to understand deeply the behaviour of organic cations in water and the sorption mechanism of organic cations by sorption materials.
以氢氧化钾为活化剂合成了具有大比表面积（2263.10 m²/g）的麦秸衍生生物炭（BC-4-700），并通过吸附亚甲基蓝（MB）和甲基橙（MO）评估其吸附性能。BC-4-700对MO和MB的吸附行为均符合准二级动力学和朗缪尔模型，两种吸附的驱动力均归因于π-π相互作用。BC-4-700对MO的最大吸附量为3.24 mmol/g，比MB的最大吸附量（2.36 mmol/g）大1.37倍。MB的等温吸附曲线存在一个拐点。普遍认为MB是阳离子染料，MO是阴离子染料。然而，这两个实验现象无法用普遍接受的MB形态很好地解释。对MB和MO溶液的pH检测实验表明，MO在水中不水解，在水中的存在形态是普遍接受的MO，而MB在水中水解，在水中的存在形态很可能包括普遍接受的MB及其水解形式。这一发现可以很好地解释上述两个实验现象，有助于深入理解水中有机阳离子的行为以及吸附材料对有机阳离子的吸附机理。
