好氧颗粒污泥对酸性红B的生物吸附模型研究

Biosorption model of acid red B on aerobic granular sludge

考察了灭活好氧颗粒污泥吸附酸性红B的吸附等温线、吸附动力学和热力学。结果表明,Langmuir和Redlich-Peterson比Freudlich吸附等温线更符合试验数据,20 ℃C时Langmuir最大单分子层吸附量为123.46 mg/g。吸附动力学符合准2级动力学模型。灭活AGS内部扩散过程用Webber-Morris模型拟合,结果表明颗粒内部扩散过程是限速步骤,但边界层扩散和动力学阻力亦不能忽略。热力学分析表明,吸附过程是吸热且自发的过程。

The paper is to introduce our simulated models for the biosorption of acid red B by aerobic granular sludge based on isotherm, kinetic and thermodynamic principles. For our research purpose, we have made detailed analysis from the point of view of isotherm, kinetic and thermodynamic principles while studying the process of the biosorption. As a result of experiments, we have found that the maximum biosorption capacity of ARB on AGS is 123.46 mg/g for the Langmuir isotherm at 20 ~C. In addition, Langmuir isotherm gave us a better description of the experimental biosorption data than the Freundlieh isotherm at all temperatures under question. However, if the whole concentration range can be divided into two sections, it would be possible for us to obtain the perfect fits to the experimental data with the Freundlich isotherm, especially at the lower concentration region. Having made careful comparison of the correlated coefficients determined for each isotherm analysis, we have found the Langmuir isotherm which helps to provide the best fit for ARB adsorption on AGS for the entire concentration range, as well as the Redlich-Peterson isotherm, though the Freundhch isotherm was able to give an excellent fit for lower concentration sections. It can also be said that, if the pseudo-second-order kinetic model could be used to describe the biosorption of ARB on AGS in the whole biosorp- tion process, it would be possible to work out the intraparticle diffu- sion ＇as the rate-controlling step by using Weber-Morris model. All the above investigation and analysis also indicate that three steps were needed to identify the biosorption process of ARB by AGS. However, since the linear lines did not pass through the origin, it may imply that the intraparticle diffusion may not be the only rate controlling step, whereas both the boundary layer diffusion and the kinetic resis~ tance may affect the hiosorption rate. Later on, we have worked out the thermodynamic parameters for the biosorption of ARB on AGS, such as free energy change （△G°）, enthalpy change （△H°） and entropy change （△S°）, with the values of △G° found as -27.15 kJ/mol, - 29.11 kJ/mol and - 32.29 kJ/mol at 20 ℃, 35 ℃ and 50 ℃. On the other hand, the values of negative △G° indicate that the ARB biosorption process is likely to occur spontaneously at all the three tested temperatures whereas the positive values of △H° and △S° reveal the endothermic nature of the biosorption process with the in- creased randomness at the solid/solution interface in the process of the biosorption of ARB on AGS.