葵花籽壳生物炭对水中Cd^(2+)的吸附研究

Adsorption of Cd^(2+) from water by biochar derived from sunflower shell

以葵花籽壳为原料,在700℃下热解制备葵花籽壳生物炭(S-BC),采用X射线衍射(XRD)、扫描电镜(SEM)、红外光谱(FT-IR)等手段对生物炭进行表征,并研究其对水中Cd^(2+)的吸附。结果表明:S-BC具有介孔结构,表面含有—C—OH、—C=O等多种官能团。当溶液pH为2—7时,随pH的升高S-BC对Cd^(2+)的吸附量逐渐增加。S-BC对Cd^(2+)的吸附速率较快,在30min时可达到吸附平衡。当吸附温度为25~45℃时,Cd^(2+)的吸附容量为30.67~40.82mg/g。吸附动力学曲线符合拟二级动力学方程,吸附等温曲线可以用Langmuir方程很好地描述。吸附过程主要为单分子层化学吸附,吸附速率由多个过程共同控制,且吸附是自发、吸热、熵增的过程。

The biochar(S-BC)derived from sunflower shell was prepared by pyrolysis at 700℃.S-BC was characterized via XRD,SEM and FT-IR measurements.And the adsorption of Cd^(2+) from aqueous solution onto S-BC was studied.The results showed that S-BC formed mesoporous structure and contained many functional groups,such as—C—OH and -C=O.The adsorption amount of Cd^(2+) increased with the pH when the solution pH was between 2 and 7.S-BC had a faster adsorption rate,reached equilibrium in 30 min.When the temperature was 25~45℃,the adsorption capacity of Cd^(2+) was 30.67~40.82 mg/g.The adsorption kinetic data followed the pseudo-second-order model.The adsorption isotherms could be well described by the Langmuir model.The adsorption process was mainly monolayer chemical adsorption,and controlled by multiple steps.Thermodynamic study showed that the adsorption reaction was spontaneous,endothermic and entropy increasing.