杨树落叶对Cd^(2+)的吸附等温线和动力学研究

Research on the Equilibrium and Kinetics of the Bio-sorption of the Dead Leaf of Plane Tree to Cadmium

[目的]研究杨树落叶作为一种价廉、高效的重金属吸附剂的可行性。[方法]用杨树落叶吸附模拟废水中的Cd2+,研究不同环境条件如重金属离子初始浓度、生物吸附剂的量、溶液温度和溶液pH对吸附效果的影响。[结果]Cd2+的初始浓度从50 mg/L增大到500mg/L时,落叶对Cd2+的最大吸附量从20.0 mg/g增长到201.2 mg/g。当溶液的pH从3增大到11时,落叶对Cd2+的吸附量逐渐从30.9 mg/g增大到40.5 mg/g。分别用Langmuir和Freundlich 2种吸附等温线模型对Cd2+的吸附过程进行拟合;用一级动力学模型、二级动力学模型和内扩散模型对Cd2+的吸附过程进行动力学研究。结果显示,Langmuir吸附等温线模型和二级动力学模型适合描述树叶对Cd2+的吸附过程。[结论]落叶对Cd2+具有一定的吸附能力,是较为理想的重金属离子吸附剂。

[Objective]The feasibility of the dead leaves of plane tree as a cheap and high-efficient adsorbent to heavy metals was studied.[Method]The dead leaves of plane tree were used to absorb the Cd2＋from simulated wastewater and the effect of the different environmental factors such as initial concentration of Cd2＋,bio-sorbent dose,temperature and pH value of solution on absorption of Cd2＋ was studied.[Results]The maximum adsorption capacity of the dead leaf to Cd2＋was increased from 20.0 mg/g to 201.2 mg/g when the initial concentration of Cd2＋ was raised from 50 mg/L to 500 mg/L in solution.The amount of Cd2＋ adsorbed by dead leaf was increased from 30.9 mg/g to 40.5 mg/g when the pH value was raised from 3 to 11.The equilibrium data were tested with Langmuir and Freundlich isotherm equations.The kinetic data were analyzed with various kinetic models：pseudo-first order equation,pseudo-second order equation and intra-particle diffusion equation.The pseudo-second order and Langmuir isotherm were proved to be suitable for the description of adsorption of plane tree leaf to Cd2＋ well.[Conclusion]The investigation showed that the dead leaf of plane tree had high adsorption capacity and could be used as an ideal absorption material for the removal of heavy metal.