Catalytic Degradation Of Dyes Using Cobalt Phthalocyanine/PAN Nanofibers

With the rapid development of industrial civilization, the problems of environmentalpollution are increasingly prominent. Among them, the problem of water pollution is particularlyacute. As a main source of water pollution, dye wastewater has the characteristics of high chroma,high COD, high BOD, multitudinous suspended solids and complicated composition. Dyewastewater is usually difficult to be biodegradable. Therefore, it is urgently needed to develop anefficient and environmentally friendly method for the treatment of dye wastewater. Advancedoxidation processes can produce strong oxidizing reactive species, which could quickly oxidateand degrade dyes and other organic pollutants, causing the researchers’ widely attention. Metalphthalocyanine has been certified that it can efficiently catalyze hydrogen peroxide, organicperoxide, oxygen to produce strong oxidizing species for oxidative degradation of organicpollutants. However, metal phthalocyanine can’t avoid forming dimer or polymer in solution,which will hinder its coordination with oxidants, leading to a decline in the catalytic activity dueto its planar ring structure. Therefore, we need to adopt a simple method to load metalphthalocyanine molecule on the supporter, which not only can prevent the metal phthalocyaninemolecule to form dimers or polymer, and improve the catalytic activity, but also can solve theproblem of recycling of metal phthalocyanine.In this dissertation, cobalt tetraaminophthalocyanine (CoTAPc), cobalt phthalocyanine(CoPc) and cobalt nitrophthalocyanine (CoTNPc) were dissolved in N-methyl-2-pyrrolidone(NMP), respectively, and polyacrylonitrile (PAN) was also dissolved in the above solution,respectively. Finally, we got the nanofibers (CoTAPc-PAN-F、CoPc-PAN-F and CoTNPc-PAN-F)loaded with the above-mentioned three types of cobalt phthalocyanine by electrospinning afterwell blended. We mainly studied the CoTAPc-PAN-F’s catalytic performance of oxidativedegradation of acid dye AR1in the presence of hydrogen peroxide (H2O2) and potassiumperoxymonosulfate (PMS). The effects of pH value, temperature, concentration of oxidant,concentration of catalyst on catalytic efficiency were investigated, respectively. And the catalyticproperties of the three different tpyes of substituent cobalt phthalocyanine nanofibers weretransversely compared. The mechanisms of H2O2and PMS catalytic decomposition byCoTAPc-PAN-F were preliminaryly discussed and the recycling performance of CoTAPc-PAN-F were also investigated. The specific research contents and results are listed as follows:1. H2O2and PMS could be effectively catalyzed to degrade acid dye AR1byCoTAPc-PAN-F. In the pH range of8~10borate buffer, CoTAPc-PAN-F exhibited the bestcatalytic performance to H2O2at pH8.5. In the pH range of4~7phosphate buffer,CoTAPc-PAN-F exhibited the better catalytic performance to PMS with the pH rising.2. The order of three different tpyes of substituent cobalt phthalocyanine nanofibers’catalytic performance to H2O2and PMS is CoTAPc-PAN-F> CoPc-PAN-F> CoTNPc-PAN-F.We think it is the substituent effect that led to the different catalytic performance of the threetpyes of substituent cobalt phthalocyanine nanofibers. Amino has a strong electron-donating abilitywhile nitro has a strong electron-withdrawing ability. Due to the strong electron-donating ability, H2O2isapt to be heterolytically cleavaged to generate high-valent cobalt-oxo intermediates while PMS is aptto generate active oxidizing species SO4–and HO.3. By adding active capture agent IPA and NaCl, the mechanisms of H2O2and PMScatalytic decomposition by CoTAPc-PAN-F were preliminaryly discussed. We infer thatCoTAPc-PAN-F could catalyze H2O2to generate high-valent cobalt-oxo intermediates as the mainactive species while HO was not generated during the catalysis. CoTAPc-PAN-F could catalyzePMS to generate SO4–and HO as the main active species.4. By evaluating the reuse performance of CoTAPc-PAN-F, we find out that its catalyticactivity to H2O2showed no obvious decrease after five successive runs, means the catalyst has agood reuse performance to catalyze H2O2. While its catalytic activity to PMS showed obviousdecrease after two successive runs, means the catalyst has a poor reuse performance to catalyzePMS. We hypothesize that the main active species SO4–and HO were destroying the CoTAPcon the surface of CoTAPc-PAN-F at the same time as decomposing AR1, leading to a decline inthe catalytic activity to PMS. Therefore, CoTAPc-PAN-F apply to catalyze H2O2, rather thanPMS to degrade dye and other organic pollutants.