Effects Of Ions Doped And Natural Zeolite Support On The Photocatalytic Activity Of TiO₂

Photocatalytic degradation and mineralization of organic andinorganic pollutants on the semiconductor n-TiO₂ have beenextensively studied in order to solve environmental problems relatingto waste waters and polluted air, because of its physical and chemicalstability, low cost, ease of availability non-toxicity, and electronic andoptical properties. However, there are still basic problems to be solvedfor improving the photocatalytic activity of TiO2 under Solar. Becausethe semiconductor TiO2 has high band gap (Eg=3.2eV), it is excitedonly by UV light (λ<387nm) to inject electrons into the conductionband and to leave holes in the valence band. Thus, this practicallylimits the use of sunlight or visible light as an irradiation source inphotocatalytic reactions on TiO₂. In addition, the high rate ofelectron-hole recombination on TiO₂ particles results in a lowefficiency of photocatalysis. And the nano TiO₂ is hard to be recycledand reused on the photcatalytic process. For the purpose ofovercoming these limitations of TiO₂ as h photocatalyst. Our studieshave been formed to enhance electron-hole separation and to extendthe absorption range of TiO₂ into the visible range by ion doped.Meanwhile, we loaded TiO₂ and doped TiO₂ photocatalysts on naturalzeolite.In this article, Iron ion and Nitrogen ion doped titaniumphotocatalyst powders were prepared by FeCl3 or urea mixing TiCl4.And the porous natural zeolite has been employed as the TiO2 supports.The photocatalytic process of various photocatalysts (e.g. TiO2,Fe-TiO2, TiO2/zeolite, Fe-TiO2/zeolite, TiO2-xNx, TiO2-xNx/zeolite) onMethyl Orange (MO) have been studied.Not only mechanism and action of ions doped TiO2 for enhancevisible light photocatalytic activity has been studied, but also theinterface mechanism between the TiO2 and the natural zeolite has beendiscussed. The visible light activity of TiO2 and reusing of nano TiO2has become ture.The photocatalytic degradation experiment results of MO, showsthat the activity of ions doped TiO2 has certainly increased both theSolar and UV light. But the results of photocatalytic degradation MOhas remarkably enhance for ions doped TiO2 catalyst under Solar light.In this paper, we considering analyze and discussed the cause ofthe activity of photocatalyst for enhancing. Using Methyl Orange asorganic contaminant model, by marking contrastive photocatalyticexperiment, it was found that the photocatalytic activity was muchhigher when ions doped TiO2 was at proper percent. However, thephotocatlytic activity declines when too much ions is doped in thetitanium dioxide. The optimum conditions for photocatlyticdegradation were also drawn out by investigating the effects of theions doped contentment and the calcining temperature. Thus, theoptimum contentment for Fe doped is about at 2.5×10-6 mol/g-TiO2and for Nitrogen doped is about at 7.2×10-6 mol/g-TiO2.The photocatalysts were characterized by XRD, AFM, FTIR,XPS and Visible Adsorption Spectrophotometer. Meanwhile, fromXRD spectra analysis shows that the more is contentment of ionsdoped the higher temperature for phase exchange of TiO2. The effectof pH on photocatalytic activity of samples and on properties ofadsorption has been studied. The optimum pH of photocatalyticdegradation MO system was drawn out.The AFM, XRD, FTIR and ions exchange of various samplesanalysis, shows that a certain amount of TiO2 combined with naturalzeolite by Ti-O-Si or Ti-O-Al, which does benefit for both thedurability of loading and the adsorption ability can also be remained inthe zeolite support compound photocatalyst. However, stability ofzeolite has declined.The visible light adsorption spectra analysis, shows that ionsdoped TiO2 photocatalyst has visible activity of photocatalytic, theexited wavelength has red shift to visible light regions, and the morecontent of ions doped, the wider the exited wavelength. So, theutilization ratio of Solar has been enhanced. Meanwhile, the XPSspectra analysis, shows that we can prepare Nitrogen ion doped onTiO2 by Sol-Gel from TiCl4 and Urea. And the preparation costing ofN doped TiO2 photocatalyst has been reduced.Comparison photocatalytic degradation MO ratio of after orbefore supported and considering the reusing experiment resultsanalysis, shows that the loading effects of natural zeolite increase boththe activity and the anti-death ability of the photocatalyst. Thus, thephotcatalytst samples can be recycled and be reused, and thephotocatalytic activity can also be remained in the zeolite supportcompound photocatalyst.The results of pre-heating treatment and water-dipping treatment,show that the pre-heating treatment is propitious to enhance theorganic transfer process, especially at the higher initial concentrationof MO, resulting in the increase the photocatalytic degradationreaction rate, and the water-dipping treatment preserves most of theopen pores of natural zeolite successfully, resulting in the increase ofthe transfer process of organic between the photocatalyst and zeolite.Comparing with the pre-heating treatment, the water-dipping treatmentis superior since it retains the open pores of raw zeolite.To sum up, ions doped titanium dioxide or ions doped TiO2coated on zeolite were prepared by a simple Sol-Gel. The dopedphotocatlyst not only enhance the ratio of electrons and holesseparation, but also increase exited wavelength of TiO2 shifts to visiblelight regions by ions doped. And the temperature of phase transfer hasincrease by ions doped, meanwhile enhances the activity of TiO2photocatalyst. The photocatalyst can combine with natural zeolitethrough chemical bonds. The addition of natural zeolite supportsincrease of photocatalytic efficiency of photocatalyst. The adsorptionability of the pores zeolite supports have enhanced the organic transferprocess during the photocatalytic degradation reaction, resulting in theincrease of the photocatalytic degradation rate of MO. Morever, theloading effects of natural zeolite increase the nati-death ability of thephotocatalysts.