棉花秸秆黑炭对Cd^(2+)的吸附特性研究

Adsorption characteristic of Cd2+by black carbon derived from cotton straw

以棉花秸秆黑炭(以下简称黑炭)为吸附剂,通过吸附动力学、吸附热力学以及等温吸附实验研究了黑炭对Cd^(2+)的吸附特性。结果表明,Cd^(2+)在黑炭上的吸附动力学更加符合准二级动力学方程,其吸附可分为快速吸附和慢速吸附两个过程,在60min就可以达到饱和吸附量的92%。颗粒内扩散并不是控制吸附速率的唯一步骤,同时受到液膜扩散和表面吸附的作用。吸附等温线拟合发现Langmuir方程能更好地描述Cd^(2+)在黑炭上的吸附行为,Cd^(2+)在炭变化时间为3.0、4.5h的黑炭上的最大吸附量分别为36.36、38.61mg/g。吸附热力学研究结果表明,黑炭对Cd^(2+)的吸附是自发的吸热过程。

Batch adsorption experiments were carried out to evaluate the adsorption kinetics and thermodynamics characteristic of Cd 2+by black carbon derived from cotton straw.The results showed that the kinetics of the removal of Cd 2+was in agreement with a pseudo-second-order equation,where it could be divided into fast and slow adsorption stages.The adsorption capacity reached 92%of the saturated adsorption capacity after 60 min.Intra-particle diffusion was not the only step to control the adsorption of Cd 2+by black carbon.It might be a combined action of internal diffusion and surface adsorption.The adsorption isotherm was described well by the Langmuir equation,and the maximum adsorption quantities of Cd 2+by two kinds of black carbon with carbonization time of 3.0 and 4.5 h were 36.36 and 38.61 mg/g,respectively.Thermodynamics analysis suggested that Cd 2+adsorption onto black carbon was spontaneous and endothermic process.