活性污泥胞外聚合物（EPS）对Pb2+吸附性能的研究

以活性污泥中提取的胞外聚合物(EPS)作为吸附剂,考察了pH、EPS投加量及温度对Pb2+吸附效果的影响,通过响应面法对其吸附条件进行优化,并对其热力学吸附特征和吸附动力学进行了探讨。研究结果表明,EPS对Pb2+的最佳吸附条件组合为:温度35℃,pH4.2,m(EPS):m(Pb2+)=2.5:1,在此条件下Pb2+实际去除率达到89.16%。EPS对Pb2+的吸附等温线能较好地用Langmuir方程和Freundlich方程来描述,但更适合用Langmuir方程拟合,3种不同温度下(20、30、40℃)最大单分子层吸附量分别为0.9229、1.0129、1.1191mg·mg-1。EPS对Pb2+的吸附过程可以用准二级动力学方程描述,并在240min达到吸附平衡,平衡时理论最大吸附量为0.45mg·mg-1。

The Characteristics Study on Adsorption of Pb2+ by Extracellular Polymeric Substances from Activated Sludge

The adsorption property on lead ions was studied using extracellular polymeric substances(EPS) as adsorbent,which was extracted from activated sludge.The parameters affected the adsorption rate were investigated and optimized via a response surface method,such as solution pH,dosage of EPS and temperature.The thermodynamic and kinetic absorption characteristics of EPS for lead ions were also discussed.Results showed that the optimal adsorption condition was at 35 ℃,pH4.2 and m(EPS):m(Pb2+) was 2.5:1.Under the optimum condition,the actual adsorption efficiency of lead ions by EPS could reach 89.16%.The absorption isotherm of lead ions by EPS could be described by both Langmuir and Freundlich model.But the Langmuir model was more accurate than the Freundlich model.According to the Langmuir equation,the maximum adsorption amount at the temperature of 20,30 and 40 ℃ can be expected to reach 0.922 9,1.012 9,1.119 1 mg·mg-1 when adsorption equilibrium,respectively.The adsorption amount increased with the rise of temperature showed that temperature was beneficial to the adsorption process and the process of adsorption of lead ion by EPS was an endothermic process.In addition,the adsorption process fitted well with pseudo-second order equations.The adsorption equilibrium could be reached at the time of 240 min with the maximum theoretical absorption amount of 0.45 mg·mg-1.