Preparation And Photocatalytic Property Of Polymer/TiO₂ /MMT Nanocomposites

As a semiconductor material, TiO2 has the distinctive photocatalytic property. As reported that TiO2 can photodegradate nearly all organic marerials with high oxidation ability and light conversion efficiency.What’s more, with the low price, strong practicability and long term chemical stability, TiO2 becomes the most promising photocatalyst applied in wastewater treatment and air purification to prevent the secondary pollution effectively. A significant step of photocatalytic oxidation is that the pollutant molecules must be gathered over the surface of TiO2 and effective collision with it.Montmorillonite(MMT) is an inorganic salt with the layered structure, which can be the substrate to avoid the aggregation when TiO2 particles are immobilized onto it through the ion exchange reaction. Moreover, MMT can improve the stability and separability of the organic-inorganic nanocomposite.Templating is an effective method for the synthesis of materials with specific size and morphology.When cellulose and cellulose grafted polymer as the template, not only can they control the size and morphology of synthesized TiO2, but also can strip the layers of MMT, thus TiO2 can adsorb the UV light effectively and enhance the adsorption-photodegradation efficiency.Our paper focused on the synthesis of polymer/TiO2/montmorillonite nanocomposites with MMT as the substrate and cellulose and cellulose grafted polymer as the templates through a conventional free radical polymerization and sol-gel method at low temperature and then characterized them. The performances of the organic-inorganic nanocomposites in photodegradating organic dyes and chlorine phenolics were studied.The main contents are as follow:1. The cell-g-Poly(4vp)/TiO2/MMT nanocomposite was synthesized based on cellulose(cell), butyl titanate(TBT) and montmorillonite(MMT) as the originalmaterials through grafted-intercalated polymerization and sol-gel method at low temperature. FT-IR spectra proved the successful immobilization of TiO2 on MMT.XRD patterns indicated the existence of anatase TiO2 and the effective stripping of MMT layers. SEM showed the different impacts of cell and cell-g-P4 vp templates on the morphology of prepared TiO2. TEM characterization proved the successful intercalation of cell-g-P4 vp into MMT. The nanocomposite exhibited efficient adsorption-photodegradation activity for methyl orange dye(MO) under 254 nm, 30 W UV light. The best photodegradation of MO is when the pH value of the solution is 4,initial concentration is 100 mg/L and quantity of photocatalyst is 0.20 g.Nanocomposite has the prior photodegradating and separating ability to the commercial TiO2. The photodegradation process conforms to the first order kinetics and has the faster photodegradation rate under the lower concertration of MO.2. The cell-g-Poly(MMA)/TiO2/OMMT nanocomposite was synthesized based on cellulose(cell), butyl titanate(TBT) and organic montmorillonite(OMMT) as the original materials through grafted-intercalated polymerization and sol-gel method at low temperature. FT-IR spectra proved the successful immobilization of TiO2 on MMT. XRD patterns indicated the existence of anatase TiO2 and the effective stripping of MMT layers. SEM showed the different impacts of cell and cell-g-PMMA templates on the morphology of prepared TiO2. TEM characterization proved the successful intercalation of cell-g-PMMA into MMT. The nanocomposite exhibited efficient adsorption-photodegradation activity for 2,4-DCP under 254 nm, 30 W UV light. The best photodegradation of 2,4-DCP is when the pH value of the solution is 6,initial concentration is 100 mg/L and quantity of photocatalyst is 0.10 g.Nanocomposite has the prior photodegradating and separating ability to the commercial TiO2.The photodegradation process conforms to the first order kinetics and has the faster photodegradation rate under the lower concertration of 2,4-DCP.3. Here we solved the problem that the organic-inorganic nanocomposite wouldbe degraded under long term UV irradiation after several cycle photodegradation through calcination. The cell/TiO2, cell-g-P4vp/TiO2, cell-g-PMMA/TiO2,cell-g-P4vp/TiO2/MMT and cell-g-PMMA/TiO2/OMMT were all calcinated under air and nitrogen atmosphere respectively and then the morphology and photodegradation ability were also studied. The experiments proved that the products after calcination under nitrogen atmosphere have some irregular pore structure and have better adsorption capacity, but the photodegradation ability was poorer. The products after calcination under air atmosphere have the poorer adsorption capacity, but their photodegradation ability was better compared with the products after calcination under nitrogen atmosphere and need more long time to photodegrade the pollutant completely compared with the original nanocomposite. In conclusion, the original nanocomposites cell-g-P4vp/TiO2/MMT and cell-g-PMMA/TiO2/OMMT were both with the best performance in adsorping-photodegrading MO and 2,4-DCP molecules.