秸秆焚烧物对黄土吸附五氯酚的影响研究

摘要

In order to study the adsorption of environmental endocrine disrupters onto loess soil affected by adding straw burning residual,pentachlorophenol (PCP) was selected as the target pollutant,to explore the adsorption kinetics,desorption kinetics,adsorption thermodynamics,and influence factors,such as particle size,initial concentration,ionic strength,pH values,by batch adsorption experiments.The results showed that the present of burning residual could promote the adsorption amounts of PCP on loess soil,and adsorption kinetics was fitted well with Pseudo-second-order model.The adsorption thermodynamics was more in line with the Freundlich adsorption model,and the adsorption isotherm conformed to the C-type.At the temperature range of 25～45℃,the average adsorption free energy (E) of PCP onto loess soil was less than 8kJ/mol,which indicates physical adsorption in the adsorption process.The adsorption free energy,such as Gibbs free energy,enthalpy and entropy were all less than zero,demonstrating a spontaneous adsorption process and the chaos degree of the system decreased.When the pH value between 3 and 7,the adsorption capacity of PCP decreased with the increase of pH values,and it was increase when the pH value between 7and 10.The adsorption capacity of PCP onto loess increased with the decrease of soil particle sizes.The adsorption capacity of PCP was increased with ion strength at the same ions situation,and when the concentration of ions is equal,the adsorption increases with the increase of the ion valence state.%为研究添加秸秆焚烧物对黄土吸附环境激素的影响,以五氯酚(PCP)为目标污染物,采用批量实验法研究了PCP在黄土与添加秸秆焚烧物黄土上的吸附动力学、吸附热力学以及初始浓度、离子强度、粒径、pH值等影响因素.结果表明:添加秸秆焚烧物促进黄土对PCP的吸附,黄土与添加秸秆焚烧物黄土的动力学均较好的符合准二级动力学模型;其热力学吸附过程均更符合Freundlich吸附模型,且吸附等温线符合C-型;温度在25-45℃时,PCP在黄土与添加秸秆焚烧物黄土上的吸附平均自由能(E)小于8kJ/mol,说明其对PCP的吸附主要以物理吸附为主;PCP的吉布斯自由能△Gθ、焓变△Hθ和熵变△Sθ均小于0,表明该吸附属于自发放热且混乱度减小的过程;当pH值在3～7范围内时,PCP的吸附量随pH值升高而逐渐减小,而pH值在7～10范围内时,其吸附量逐渐增大;黄土对PCP的吸附量随其粒径的减小而增大;离子相同时,其浓度越高越有利于PCP的吸附;离子浓度相同时,黄土对PCP的吸附量随其价态的升高而增加.