| Triphenylmethane dye is a kind of compounds which have some benzene rings, and is widely used in textile, leather products and staining agent. This kind of dye is carcinogenic, teratogenic and mutagenic. Its emission by producing, transporting and applying, leads to environmental pollution. Therefore, it is of important theoretical and practical significance to search for effective treatment methods for these highly toxic contaminants. It is believed that zero valent metal has wide application prospect due to its efficiency in reductive degradation of many organic products, along with low cost and simple processes. This paper mainly studied the factors and reaction mechanism of the degradation of malachite green by zero valent zinc alone and in the presence of small molecular organic acid (citric acid).Part Ⅰ:At pH4.0-6.0, the factors and reaction mechanism of decolonization of malachite green were investigated by batch experiments. The results showed that the decolonization of malachite green by zero valent zinc alone was effective. The reaction of decolonization of malachite green by zero valent zinc obeys to pseudo-one-order kinetics. Under experimental conditions, the decolonization of malachite green was best at pH6.0, and the degradation rate constant in the presence of zero valent zinc at pH6.0was1.5times as much as that of pH4.0. The pH value of reaction solution, temperature and the amount of zero valent zinc were the important factors which affected the decolonization of malachite green. And this paper conjectured the intermediates according to the data obtained by LC-MS and proposed a possible reduction mechanism.Part Ⅱ:At pH4.0-6.0, the degradation of malachite green by zero valent zinc in the presence of citric acid was conducted. The results showed that the degradation of malachite green was enhanced with proper citric acid addition at pH4.0. The reaction of degradation of malachite green also obeyed to pseudo-first-order kinetics. |
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