纳米α - Fe2O3微球对U(Ⅵ)的吸附特性研究

将海藻酸钠与纳米α-Fe2O3制成微球,用于吸附U(Ⅵ)。探讨了纳米α-Fe2O3含量、交联时间、pH值、投加量、浓度、温度等对吸附的影响。结果表明,pH值对U(Ⅵ)的吸附过程影响显著,适宜pH值为3。U(Ⅵ)在微球上的吸附量随着吸附时间的增加而增大,初始阶段(1.5 h)反应进行得很快,9 h时达到吸附平衡。当U(Ⅵ)初始质量浓度为10mg/L时,其饱和吸附量为2.64mg/g。准二级动力方程很好地拟合了吸附动力学数据,且R2>0.99。吸附率与温度呈正相关,Lang-muir与Freundlich吸附等温方程均能较好地拟合固定化微球对U(Ⅵ)的吸附过程(R2>0.99),但Freundlich等温线效果更好。吸附反应中ΔG<0,ΔH>0且小于40 kJ/mol,ΔS>0,这表明吸附过程能自发进行,为吸热反应。

Adsorption of uranium ( Ⅵ ) by immobilized nano-α - Fe2O3 micro-beads

The given paper is to present our experimental results on the adsorption of uranium(Ⅵ) in the solution by nano-α-Fe2O3 micro-beads immobilized into sodium alginate(SA),which we have investigated in a batch experiment.As is known,nuclear energy,on the one hand,has brought about huge economic benefits to the world,on the other hand,it is inevitable for nuclear fuel production to generate low-level radiation waste,such as uranium and other radioactive heavy metals which are detrimental to us humans in many aspects.Therefore,strong demand has been existing to find and apply some kind of powerful adsorbent to reduce and eliminate such harmful nuclear waste to protect our environment.It is just from this need we would like to assume the task to study and analyze the effects of nano-α-Fe2O3 powders content in the particles,cross-linking time,solution pH value,adsorbent dose,initial U(Ⅵ) concentration,temperature and contact time for U(Ⅵ) adsorption.The results of our study indicate that the adsorption capacity is strongly affected by the pH value of solution with the optimal pH value being 3.Besides,we have also found that the adsorption process can be done rather quick in the initial 1.5 h,while the state of equilibrium can be reached in 9 h and the absorption capacity can get to 2.64 mg/g,with the U(Ⅵ) mass concentration of being 10 mg/L in the solution.What is more,as compared with the pseudo-first-order kinetics equation,it is possible to simulate the kinetics adsorption data better in the pseudo-second-order kinetics equation with a good correlation being R2>0.99.In addition,we have found the adsorption rate of uranium(Ⅵ) tends to increase slowly with the temperature rising,which shows that temperature has less effect on the adsorption.And,finally,it is found that the adsorption process comes into conformity with Langmuir and Freundlich isothermal adsorption models(R2>0.99),with the latter being better.And,all in all,the results of the thermodynamic parameters ΔG<0,0<ΔH<40 kJ/mol and ΔS>0 suggest that the adsorption process takes place in a spontaneous manner with endothermic,physical,hydroxyl complexation and ion exchange.