Zhang Changbo, Wang Lei, Wu Feng, Deng Nansheng
School of Resources and Environmental Science, Wuhan University, PR China.
Environ Sci Pollut Res Int. 2006 May;13(3):156-60. doi: 10.1065/espr2005.10.287.
For their high photoreactivity, Fe(III)-carboxylate complexes are important sources of H2O2 for some atmospheric and surface waters. Citrate is one kind of carboxylate, which can form complexes with Fe(III). In our previous study, we have applied Fe(III)-citrate complexes to degrade and decolorize dyes in aqueous solutions both under UV light and sunlight. Results have shown that carboxylic acids can promote the photodegradation efficiency. It is indicated that the photolysis of Fe(III)-citrate complexes may cause the formation of some reactive species (e. g. H2O2 and *OH). This work is attempted to quantify hydroxyl radicals generated in the aqueous solution containing Fe(III)-citrate complexes and to interpret the photoreactivity of Fe(III)-citrate complexes for degrading organic compounds.
By using benzene as the scavenger to produce phenol, the photogeneration of *OH in the aqueous solution containing Fe (III)-citrate complexes was determined by HPLC.
In the aqueous solution containing 60.0/ 30.0 microM Fe(III)/citrate and 7.0 mM benzene at pH 3.0, 96.66 microM *OH was produced after irradiation by a 250 W metal halid light (lambda > or = 313 nm) for 160 minutes. Effects of initial pH value and concentrations of Fe(III) and citrate on *OH radical generation were all examined. The results show that the greatest from 3.0 to 7.0) was at pH 3.0. The photoproduction of *OH increased with increasing Fe(III) or citrate concentrations.
In the aqueous solutions containing Fe(III)-citrate complexes, *OH radicals were produced after irradiation by a 250 W metal halide light. It can be concluded that Fe(III)-citrate complexes are important sources of *OH radicals for some atmospheric and surface waters.
It is believed that the photolysis of Fe(III)-citrate complexes in the presence of oxygen play an important role in producing *OH both in atmospheric waters and surface water where high concentrations of ferric ions and citrate ions exist. The photoproduction of *OH has a high oxidizing potential for the degradation of a wide variety of natural and anthropogenic organic and inorganic substances. We can use this method for toxic organic pollutants such as organic dyes and pesticides.
由于其高光反应性，铁（III）-羧酸盐配合物是一些大气和地表水过氧化氢的重要来源。柠檬酸盐是一种羧酸盐，它能与铁（III）形成配合物。在我们之前的研究中，我们已应用铁（III）-柠檬酸盐配合物在紫外光和阳光下对水溶液中的染料进行降解和脱色。结果表明，羧酸可提高光降解效率。这表明铁（III）-柠檬酸盐配合物的光解可能导致一些活性物种（如过氧化氢和羟基自由基）的形成。本研究旨在量化含有铁（III）-柠檬酸盐配合物的水溶液中产生的羟基自由基，并解释铁（III）-柠檬酸盐配合物对降解有机化合物的光反应性。
以苯作为清除剂生成苯酚，通过高效液相色谱法测定含有铁（III）-柠檬酸盐配合物的水溶液中羟基自由基的光生成量。
在pH为3.0、含有60.0/30.0微摩尔铁（III）/柠檬酸盐和7.0毫摩尔苯的水溶液中，用250瓦金属卤化物灯（波长≥313纳米）照射160分钟后，产生了96.66微摩尔羟基自由基。研究了初始pH值以及铁（III）和柠檬酸盐浓度对羟基自由基生成的影响。结果表明，在pH值从3.0到7.0的范围内，在pH为3.0时产生的羟基自由基最多。羟基自由基的光生成量随铁（III）或柠檬酸盐浓度的增加而增加。
在含有铁（III）-柠檬酸盐配合物的水溶液中，用250瓦金属卤化物灯照射后会产生羟基自由基。可以得出结论，对于一些大气和地表水而言，铁（III）-柠檬酸盐配合物是羟基自由基的重要来源。
据信，在存在氧气的情况下，铁（III）-柠檬酸盐配合物的光解在大气水和存在高浓度铁离子和柠檬酸盐离子的地表水中产生羟基自由基方面起着重要作用。羟基自由基的光生成对于降解各种天然和人为的有机及无机物质具有很高的氧化潜力。我们可以将此方法用于处理有机染料和农药等有毒有机污染物。
