UV/Fenton体系中Fe2+/Fe3+的相互转化规律

为了控制UV/Fentan方法中铁元素的用量,合理利用溶解态铁的催化反应过程并提高其降解效率,研究以难生物降解性染料罗丹明B为目标物,通过正交实验和单因素实验确定了UV/Fenton体系的最佳反应条件,并利用一元线性方程模拟了罗丹明B退色反应的的动力学方程.结果显示,当体系的最初pH为3.00,溶液中Fe2+]=0.180 mmol·L-1、H2O2]=124.022 mmol·L-1时,UV/Fenton氧化罗丹明B退色符合一级反应动力学方程.研究了总铁含量维持在0.180mmol·L-1、保持紫外光照射、4次向同一UV/Fenton体系中添加1.7mLH2O2,每次反应后Fe2+/Fe3+的循环转化规律和溶液的脱色效果.研究结果表明,每次反应结束阶段(30 min),Fe2+浓度均高于Fe3+浓度,残余液仍具有较强的催化能力,溶液的脱色率达到99.9%;退色反应速率常数始终维持在较高水平,最后一次循环反应结束后,反应速率常数达到0.2547,相对于初始反应速率常数只下降了17%左右.

Transform rules between Fe3+/Fe2+ in the UV/Fenton system

In order to reduce the over usage of dissolved Fe in the UV/Fenton system and enhance the catalytic oxidation involving Fe ions, the kinetics of oxidation of the refractory dyestuff Rhodamine B were studied through orthogonal experiments, individual factor experiments and unitary linear regression equation simulation. The results show that high degradation efficiency occurs at initial pH=3, Fe2+ concentration of 0.180 mmol·L-1 and H2O2 concentration of 124.022 mmol·L-1. The UV/Fenton degradation obeys first-order kinetics. Furthermore, cyclic transformation of Fe2+ with Fe3+ as well as degradation of Rhodamine B in the UV/Fenton system were investigated, by maintaining 0.180 mmol L-1 dissolved total Fe and ordinary UV irradiation throughout the whole reaction, while adding 1.7 mL 30% H2O2 into the residual solution four times in sequence. The Fe2+ concentration in the residual after each recycle is still higher than that of Fe3+, which implies that the system still has a high catalytic oxidation ability. It was also found that 99.9% of decoloration is observed at 30 min in each of the five cycles. The reaction rate constant for the last cycle was 0.2547 s-1, a decrease of only 17% compared to the initial rate constant.