Catalytic Fibers To Purify The Indoor Organic Pollutants

With the improvement of the people's living standards, indoor air pollution resulting from volatile organic compounds (VOCs), especially the malodors and formaldehyde, becomes more and more serious. Concerns about potential public health problems due to indoor air pollution are based on the evidence that urban residents typically spend more than 80 percent of their time indoors, so the treatment for VOCs of indoor air is imperative under the situation. In this dissertation, binuclear metallophthalocyanines (Mt₂Pc₂) were synthesized and supported on the cellulose fiber to obtain a novel functional catalytic fiber. With the aim of purifying indoor air, the representative organic pollutants of malodors and formaldehyde were used to investigate the reactivity of catalytic cellulose fiber.In this paper, octa-carboxylic metallophthalocyanine (MtPc) and binuclear metallophthalocyanine (Mt₂Pc₂) were synthesized through a phenylanhydride-urea route and characterized by infrared spectrum (IR), Ultraviolet and Visible Spectrophotometer (UV/Vis), thermalgravimetry analysis (TGA), atom absorption spectrum (AAS) and flight-mass spectrometry (MALDI-TOF). 2-mercaptoethanol was investigated as the model to evaluate the catalytic oxidation activity of MtPc and Mt₂Pc₂, and the results indicated that the catalytic oxidation ability of binuclear metallophthalocyanines was superior to that of the corresponding mononuclear metallophthalocyanines. Especially, the mononuclear phthalocyaninecopper (â…¡) almost had no catalytic oxidation activity towards 2-mercaptoethanol, while binuclear phthalocyaninecopper (â…¡) exhibited higher catalytic oxidation activity towards 2-mercaptoethanol, which attributed to the big tt conjugate system of binuclear phthalocyaninecopper (â…¡), the valence change of central copper ion and the stability of central metal ions with altertable valence depentent on phthalocyanine ring. The effects of pH, the concentration of metallophthalocyanine and temperature on the catalytic ability of binuclear phthalocyaninecopper (â…¡) were also investigated. The results showed that the initial reaction rate increased with the increase of pH from 6 to 11 and then rapidly decreased. The accelerated catalytic oxidation was attributable to the amount of the dissociative ^-SCH₂CH₂OH produced by 2-mercaptoethanol, which increased with the rise of pH below 11, while the excessive OH^-hindered the combination between ^-SCH₂CH₂OH and the central metal ion in phthalocyanine above 11, resulting in the lower reaction rate. Meanwhile, the catalytic activity of binuclear phthalocyaninecopper (â…¡) increased with the increase of the reaction temperature and metallophthalocyanine concentration. Moreover, the activation energy (Ea) was evaluated as 41.19 kJ/mol, indicating that the oxidation of 2-mercaptoethanol was an endothermic reaction in the presence of binuclear phthalocyaninecopper (â…¡).The catalytic activity of binuclear phthalocyaninecopper (â…¡) on the decomposition of hydrogen peroxide was also investigated, and the results showed that the reaction rate increased with the increase of pH above 8, while pH had no obvious effect on the reaction rate below 8. It was because the dissociation of hydrogen peroxide in alkaline solution resulted in the production of HOO-, which was easier to coordinate with the central copper ions. The logarithms of the catalyst concentration versus the initial decomposition rate of hydrogen peroxide accorded with a linear relation. Meanwhile, an interesting phenomenon was observed that binuciear phthalocyanineiron (â…¢) and binuclear phthalocyaninecobalt (â…¡) mixtures showed higher catalytic ability on 2-mercaptoethanol, which was attributed to their synergistic effect.Novel catalytic fibers (Mt₂Pc₂CF) were prepared by immobilizing binuclear metallophthalocyanines (Mt₂Pc₂) on the cellulose fiber pretreated by cationic modifier, and the optimum preparation conditions were determined as: pH8, 100℃, 60min and [Mt₂Pc₂]=0.4g·L^-1. The deodorizing property of Mt₂Pc₂CF was investigated, which showed that Mt₂Pc₂CF can efficiently eliminate mercaptan and hydrogen sulfide by catalytic oxidation. Importantly, Mt₂Pc₂CF has a better ability to be reused and recovered without obvious decrease of catalytic activity after several repetitive experiments.Another novel catalytic fiber, P-Co₂Pc₂CF, was obtained by introduing promoter into Co₂Pc₂CF. The catalytic oxidation activity of P-Co₂Pc₂CF on formaldehyde was investigated, and the effects of the amount of P-Co₂Pc₂CF, temperature, the initial concentration of formaldehyde, oxygen concentration and visible light were also discussed. The experimental results indicated that the introduction of promoter increased the catalytic oxidation activity of P-Co₂Pc₂CF on formaldehyde, which also increased with the increase of the amount of P-Co₂Pc₂CF, temperature and oxygen concentration. The visible light nearly had no effect on the catalytic oxidation activity of P-Co₂Pc₂CF for formaldehyde, which was facile to recover and reuse. The products formed in the catalytic oxidation of formaldehyde were identified by High Performance Liquid Chromatography (HLPC), Gas Chromatography (GC) and Mass Spectra (MS). The results showed that the catalytic oxidation started with the formation of formic acid, which was further mineralized to carbon dioxide and water.P-Co₂Pc₂CF can effectively eliminate indoor air pollutants of malodor and formaldehyde at normal temperature and pressure, which can be recycled. Our research provides a new thought to treat indoor air pollution, and it has great practical value and theoretical significance to solve more and more serious indoor air pollution.