高氯酸体系中肼为还原剂催化还原U(Ⅵ)的反应动力学

摘要

The kinetics of platinum-catalyzed reduction of U(Ⅳ) with hydrazine in perchloric acid media was studied. By investigating the influence of U(Ⅳ) concentration, hydrazine concentration, acidity and catalyst amounts (S/L) on the reaction, the reaction rate equation is obtained: -dc(UO22+ )/dt = kc0.39 (UO22+ )c0.36 (N2 H5+ )c-0.51 (H+ ), and the rate constant is 3. 2×10-3(mol/L)0.76/min at 60℃ and the solid-to-liquid ratio of 0. 002 kg/L. The effect of temperature was also investigated. The results show that while increasing the temperature, the reaction accelerates and the reaction process shifts from reaction-controlled to diffusion-controlled. Based on the above results, a possible reaction mechanism with the dissociation of adsorbed hydrazine on the catalyst as the the control step, is explored.%开展了高氯酸体系中以肼为还原剂,铂黑为催化剂催化还原U(Ⅵ)的动力学研究.通过考察U(Ⅵ)浓度、肼浓度、酸度以及催化剂用量等条件对反应过程的影响,确定了该反应的初始动力学速率方程为-dc(UO2+2)/dt＝kc0.39(UO2+2)c0.36(N2H+5)c-0.51(H+),在60℃、固液比0.002kg/L时,速率常数k=3.2×10-3(mol/L)0.76/min.研究了温度对反应速率的影响,结果表明,在20～75℃范围内,随着温度升高,反应速率加快,反应过程由化学反应控制转变为扩散控制过程.并在此基础上推测了可能的反应机理,认为肼在催化剂表面的吸附分解是整个反应的控制步骤.