可见光多相类芬顿降解水中孔雀石绿

为强化多相类芬顿反应的速率,采用可见光辅助树脂载铁(FeIII/R)为催化剂催化过氧化氢降解水中孔雀石绿(MG).结果表明,可见光能强化MG的降解.探讨初始pH值、过氧化氢初始浓度和MG初始浓度及叔丁醇等对反应速率的影响.叔丁醇实验表明羟基自由基和高价态铁在反应中同时存在.催化剂重复使用表明铁在树脂表面负载比较牢固,具有较好的稳定性.     

Reactive species in resin supported heterogeneous Fenton-like oxidation of Malachite green solution

During the oxidative degradation of nonbiodegradable Malachite green (MG) by means of H2O2 /FeIIIR (iron supported on ion-exchage resin) in a dynamic column,the binding energy of the Fe(2p3/2) region for XPS spectra was found to be different between the top layer and the bottom layer in this column. Based on the data from XPS spectra and DMPO-OH·signal by EPR spectra,it is shown that the formation of ferryl (IV) is the key step for the oxidation of MG. The ferryl (IV) species can oxidize MG,and its redox potential is about 0. 739 - 0. 803 V measured by cyclic voltammograms (CV) . The catalytic capability of ferryl (IV) species was also evaluated,and it is found that it can promote the decomposition of H2O2 more efficiently than ferric iron. The removal rate of MG mainly depends on the adsorption of catalyst. Both ferryl (IV) and HO·radicals are the reactive species in the system. The oxidation of HO·is only a small part of the overall removal rate. Based on the obtained results,a possible mechanism for a resin-supported Fenton-like oxidation reaction is proposed.     

铁络合物催化类Fenton氧化研究进展

综述了铁络合物催化类Fenton氧化的研究进展.铁络合物与铁相比具有更高的催化活性,可提高水中有机物的去除效果.均相类Fenton存在后续金属离子的去除问题,因此铁络合物作为催化剂的多相催化类Fenton氧化具有更好的应用前景.重点介绍了高分子负载铁络合物催化类Fenton氧化降解水中有机物的研究现状及铁络合物催化类F...     

Free Radical Mediated Cellulose Degradation during High Consistency Ozonation

Abstract

A study was performed on the ozonation of cotton linters at high consistency, 40%, and pH3, in order to shed some light on the mechanism of degradation of cellulose during pulp bleaching. Ferryl ions (FeO²⁺), produced in the reaction of O₃ with Fe(II), was used to initiate free radical chain reactions to investigate the relation between chain reactions and degradation. The degradation was evaluated by viscometry. The degradation of cellulose responded more strongly to the propagation than to the initiation of the chain reactions. Also, the results suggest that the reactions responsible for initiation do not in themselves contribute to the observed degradation. Complementary experiments were made on cellulose beads (<5% crystalline). In contrast to the results from the cotton linters, the degradation of cellulose beads appears to correspond directly to ferryl ion formation. In non‐structured cellulose (cellulose beads), cellulose is highly accessible. The degradation is thus directly linked to the total amount of radical attack. In naturally structured cellulose (cotton linters) only cellulose at fibril surfaces is accessible and will react. A chemical attack of fast‐reacting agents on surfaces in structured cellulose should thus not be highly efficient in lowering the average chain length. What distinguishes radical chain reaction degradation in this context is that the spreading chain reaction is governed by the time of each step in the reaction cycle. The explanation that best fits our results is that of a free radical chain reaction, where the propagation step is rapid, which also implies that degradation is concentrated to zones along fibrils or fibers.     

树脂负载高价铁催化H2O2降解橙黄Ⅳ

为提高多相类芬顿反应的速率,采用高价铁氧化合物(FeIVF=O/R)为催化剂,强化H2O2分解降解橙黄IV.探讨初始pH值、温度、过氧化氢初始浓度和橙黄IV初始浓度等对反应速率的影响.结果表明:随着pH值升高,橙黄IV降解率下降.在pH值3～10的范围内,能有效地对橙黄IV进行降解.催化H2O2降解橙黄IV的反应遵循一级反应动力学,反应活化能为59.94kJ/mol.反应速率常数与H2O2的初始浓度及与橙黄IV初始浓度都具有很好的正相关性.催化剂重复使用表明铁在树脂表面负载比较牢固,具有较好的稳定性和耐用性.