水污染治理K_(2)CO_(3)-尿素活化毛竹制备分级多孔炭及其对RhB的吸附作用

Preparation of hierarchical porous carbon from bamboo activated by K_(2)CO_(3)-urea and its adsorption for RhB

以毛竹粉为原料,低腐蚀性K_(2)CO_(3)和尿素作为活化剂,制备毛竹基活性炭(PAC),分别利用SEM和N_(2)物理吸附仪(Autosorb-iQ)表征活性炭的表面形态和微观孔结构特点,研究不同p H值、时间和PAC用量等因素对PAC吸附RhB性能的影响,并分析其吸附规律。结果表明,当毛竹粉、K_(2)CO_(3)和尿素的质量比为4∶2∶1,热解温度为600℃,活化时间为60 min时,PAC具有微-介孔共存、高比表面积(2 554.85 m^(2)/g)和总孔容大(0.98cm^(3)/g)的特点。PAC对Rh B表现出良好的吸附效果,45℃时最大静态平衡吸附量达到707.29mg/g,且准二级动力学模型对PAC吸附RhB具有更好的拟合性,即吸附过程以化学吸附为速度控制步骤;吸附等温线试验则表明,Langmuir和Freundlic这2种模型与吸附过程均有较高的拟合度,但Langmuir模型的R^(2)更接近1,属于以单层吸附为主同时存在非均匀多层吸附的行为;热力学结果分析表明,PAC对RhB吸附过程的△G°<0,△H°>0,△S°>0,说明吸附行为是自发进行,且以化学吸附为主。

Phyllostachys edulis based activated carbon(PAC)was prepared by activation modification with K_(2)CO_(3)-urea as activator under high temperature calcination,and its adsorption performance for Rhodamine B(RhB)was discussed.SEM and N_(2) physical adsorption instrument(Autosorb-iQ)were used to characterize the surface morphology and micro pore structure of activated carbon.The effects of initial pH value,time and the amount of activated carbon on the adsorption performance were studied.The adsorption mechanism behavior of PAC on RhB was analyzed by the adsorption kinetics,adsorption isotherm and adsorption thermodynamic.The results showed that when the mass ratio of P.edulis,K_(2)CO_(3) and urea was 4∶2∶1,the pyrolysis temperature was 600℃,and the activation time was 60 min,the prepared BAC had the characteristics of hierarchical porous structure,high specific surface area(2554.85 m^(2)/g)and large total pore volume(0.98 cm^(3)/g),and showed good adsorption effect on RhB,with the maximum adsorption capacity of 707.29 mg/g.The adsorption kinetics and isotherms were in accordance with the quasi second order kinetic model and Langmuir model respectively,indicating that the adsorption process is a single-layer adsorption dominated by chemical adsorption.The standard parameters changes of free energy(△G°<0),entropy(△S°>0)and enthalpy(△H°>0)in adsorption processes have been calculated,and it demonstrated that the adsorption behavior,indicate that the adsorption of RhB by PAC is a spontaneous endothermic process with obvious thermodynamic characteristics of chemical adsorption.