Research On Modified Of Visible Light Response Environmental Purification Materials

Along with the fast development of the industry and technology, the shortage of energy and environmental problems become urgent in daily life threatening the sustained development. The solar energy is a clean and renewable energy and its utility may solve the shortage of fuel and various pollution questions at the same time.Developing novel visible light respondent photocatalystic material plays the key role in the photocatalystic area. Recently, some polymer semiconductor photocatalysts including g-C3N4 were found to efficiently degrade organic pollutants and split water generating hydrogen under visible light. Much effort was then focused on further extending the adsorption of these materials for visible light and modifying the electronic band structure to enhance their photocatalytic performance.So far, chemical doping nonmetal elements such as P, F, or S in g-C3N4 have been reported to be an effective strategy for improving its photocatalytic activity. Among them, the most elusive dopant is element sulfur; its modulation of the optical absorption property and electronic band structure of g-C3N4 is very dependent on the type of sulfur precursor and synthetic routes. Sulfur has been doped into the framework of g-C3N4 by post-treating g-C3N4 in the H2S atmosphere; it was found that the homogeneous substitution of sulfur for lattice nitrogen led to a widened valence band (VB) and an increase in the conduction band (CB) minimum (CB) of g-C3N4. However, using a simple sulfur-containing compound such as thiourea, inorganic salt (ammonium thiocyanate), or elemental sulfur (S8) as the precursor in sulfur-mediated synthesis was identified the absence of S species in the resulting carbon nitride photocatalysts. These results imply that the underlying cause of sulfur doping in modifying the electronic band structure and optical properties of polymer semiconductor photocatalysts is meaningful and deserves further inquiry.Amount many photocatalysts, it was found that the novel photocatalyst polyimide also showed the property of low-cost, facile synthesis and environmental harmony and became the focus in our work. Meanwhile, sulfur-doped polyimide (SPI) photocatalysts were synthesized for the first time via an in situ thermal copolymerization method using sublimed sulfur (S4) as a dopant. The doped sulfur substitutes for the lattice nitrogen in triazine rings of PI to form the S-C bond and changes the distribution of negative charge in the two-dimensional plane of PI. Sulfur doping not only extends the absorption range of polyimide (PI) for visible light but also enhances the oxidation ability of the photoinduced hole of PI and shows an effective suppression to the recombination of electrons and holes in PI. The photocatalytic activity of SPI in the degradation of methyl orange is three times of PI in that. The free-metal novel polymer photocatalytic material has excellent recyclable use and degrades pollutants under visible light irradiation. Herein, it may be wildly applied in the future.Furthermore, we applied with a solution synthetic method to obtain the high surface area polyimide. So we used it as an adsorbent to adsorb MO to purify the environment. It turns out that PI has the potential to be an excellent adsorbent. The mass adsorption amount is about 200mg/g. Then, we obtain the adsorption isotherms of PI-Freundlich isotherm and Langmuir isotherm and find out the adsorbed process suits with Langmuir isotherm. Several models are exerted to investigate the details of the MO adsorption process onto PI, which include the pseudo-first-order model, the Ho pseudo-second-order model film diffusion model and the intra-particle diffusion model. The result indicates that the pseudo-second-order kinetic model give a better correlation for the adsorption of MO on PI compared to that of the pseudo-first-order model.