玉米芯生物炭的制备及其对水中罗丹明B的吸附性能

Preparation of Corn Cob Biochar and Its Adsorption Performance on Rhodamine B in Water

选用废弃玉米芯为原料,通过限氧热解法在600℃下制备玉米芯生物炭(CCB_(600))用于吸附水中罗丹明B(Rh B),在对CCB_(600)进行结构表征的基础上,通过序批实验对吸附影响因素、动力学、等温线及热力学进行了研究。结果表明,CCB_(600)具有较高的碳化水平、芳香性和良好的生化稳定性,比表面积高达22. 35 m^(2)/g,总孔容为0. 048 cm^(3)/g,同时含有—OH、C=O、C—O等含氧官能团,可为其吸附Rh B提供有利条件。在反应温度为25℃、溶液初始p H值为3. 0、CCB_(600)投加量为0. 4 g/L、Rh B初始浓度为20 mg/L时,吸附210 min后基本达到平衡,Rh B去除率超过94%。采用准二级动力学模型和Freundlich模型能更好地描述CCB_(600)对Rh B的吸附行为,吸附过程包括了快速吸附、慢速扩散和吸附平衡3个阶段,属于多分子层非均相吸附,颗粒内扩散不是唯一的控速步骤。Rh B在CCB_(600)上的吸附行为是自发的,且是吸热和熵增加的过程,吸附反应以化学吸附为主,与氢键和π—π键的作用密切相关。CCB_(600)可为水中Rh B的去除提供一种有价值的吸附材料。

Corn cob biochar(CCB_(600))was prepared for the adsorption of Rhodamine B(RhB)in water by oxygen-limited pyrolysis at 600℃.The adsorption factors,kinetics,isotherms and thermodynamics were investigated by sequential batch experiments based on the structural characterization of CCB_(600).The results showed that CCB_(600) had a high level of carbonation,aromaticity and good biochemical stability,with a high specific surface area of 22.35 m^(2)/g and a total pore volume of 0.048 cm^(3)/g.It also contained oxygen-containing functional groups such as—OH,C=O and C—O,which can provide favourable conditions for its adsorption of RhB.At a reaction temperature of 25℃,an initial pH of 3.0,a dosage of 0.4 g/L of CCB_(600) and an initial concentration of 20 mg/L of RhB,the adsorption reached equilibrium after 210 min,and the removal rate of RhB exceeded 94%.The quasi-secondary kinetic model and the Freundlich model could better describe the adsorption behaviour of RhB onto CCB_(600).The adsorption process included three stages:fast adsorption,slow diffusion and adsorption equilibrium,which were non-homogeneous adsorption of multiple molecular layers,and intraparticle diffusion was not the only rate-controlling step.The adsorption behaviour of RhB onto CCB_(600) was spontaneous and was a process of heat absorption and entropy increase.The adsorption reaction was chemisorption based and was closely related to the action of hydrogen andπ—πbonds.CCB_(600) may provide a valuable adsorbent material for the removal of RhB from water.