【摘要】 以聚丙烯酰胺(PAM)为絮凝剂,纳米TiO2为固定化酶载体材料,木瓜蛋白酶为酶模型制备纳米絮凝酶.结合粒度分析、SEM、EDS等表征手段,考察PAM种类、加量及体系pH对高分子凝胶絮凝与沉降动力学的影响.结果表明通过氢键、静电吸附和架桥等作用,纳米酶和PAM间产生有效的絮凝.TiO2纳米酶的絮凝沉降速度、体系浊度、絮团大小和紧实程度随PAM用量不同而改变.适量的PAM产生高沉降速度,低浊度,稳定、大絮团的强絮凝,其中nPAM絮凝酶的沉降速度最快,絮团最大.过量的絮凝剂导致絮团脱稳.调控体系酸碱度亦可有效调控PAM絮凝动力学行为.比较nPAM和cPAM,发现nPAM絮凝体对pH有较高稳定性,cPAM絮凝体受pH影响显著.故可以根据酶结构与特性,调节絮凝剂加量和体系酸碱度设计出微纳尺度可调的固定化酶.更多还原

【Abstract】 TiO2-enzyme microfloccules were prepared by using titanium dioxide nanoparticles as immobilizing carriers,three kinds of polyacrylamide(nonionic,cationic and anionic polyacrylamide) as flocculants and papain as a model of enzyme.The effects of pH values,dosage and types of polyacrylamide(PAM) on the flocculation and sedimentation behaviour of TiO2-enzyme microfloccules were investigated.The SEM,EDS and particle size analyzer were used to characterize the morphology of TiO2-enzyme microfloccules.The results showed that an effective flocculation was formed among TiO2,papain and different types of PAM flocculant by hydrogen bonding interactions,electrostatic attractions,adsorption bridging action,etc.It was noted that the settling rate of TiO2-enzyme microfloccules,turbidity of the supernatant,floc size and compactness of resulting floccules were highly dependent on the PAM dosage.For three kinds of PAM,similar trends of flocculation kinetics were observed,a general increase in settling rates were relevant to decrease in turbidity.Attributed to high settling rates,strong flocculation with big size and stable floc occurred with the function of optimum PAM concentrations.But the optimum dosages were different.When the concentration was in the range of 75 mg L-1 to 175 mg L-1,nonionic PAM(nPAM) displayed the best flocculant performance in all kinds of PAM with a rapid settling rate and large floc size.Moreover,under excessive dosage condition,breakup of floc then occurred.Flocculation kinetics of TiO2-enzyme microfloccules also could be effectively controlled by changing the pH value of reaction system.Compared nPAM with cationic PAM(cPAM),the microfloccules by using nPAM displayed a high stability and compactness in a wide range of pH values.The settling rate and floc size by using cPAM showed a strong dependence on pH values.It indicated that the immobilized enzyme size could be regulated by the PAM dosage and pH value according to the enzyme structure and properties.Such porous and flexible microstructure was expected to provide the free space as much as possible for the access of substrate molecules to enzyme.更多还原