Preparation And Proprerties Of Multimineral Photocatalystical Material Fe～(3+) Doped TiO₂/montmorillonite

Since the discovery of photoelectrochemical splitting of water on n-TiO₂ electrodes by Fujishima and Honda at 1972,n-type semiconductor heterogeneous photocatalytic technology has attracted much attention on TiO₂,which is non-toxic,innocuity,without thrill ,has well chemical stability,and quite high photocatalytic activity and the general use in the degradation of most organic pollutants,so it has gained a abroad attention of people in the dealing with the castoff pollutants,especially in the degradation of organic pollutants in the water with low concentration and high nocuousness.Natural bentonite is a kind of layered silicate which has the major component of montmorillonite,there is a layer lap of 1nm between the interior layer. Utilizing the strong ion exchange property and structural characteristics of bentonites,we can prepare the composite photocatalysts with nanometer.It has the properties of a large surface area,larger quantity of tiny holes,well heat tolerance,high surface acid property,and that its raw meterial has abundant source and low price.It is a high efficient supported photocatalysts which also has high selectivity.Due to montmorillonite's better cation exchange capacity and absorpion,the photocatalyst meterial of inorganic ion pillared montmorillonite has been payed attention by some scholars. Montmorillonite pillared by TiO₂ not only has the large quantity of porous structures and larger specific surface area,but also has the TiO₂ crystal grain which has the photocatalytic activity of semiconductor.In the process of the degradation of organic pollutants,it can overcome the difficulty of the reclaim of TiO₂ power and the disadvantage of the badly repeated use.So resently it has become the hotspot with the study of the montmorillonite pillared material. The montmorillonite in bentonite has large surface area,well adsorption property and excangeability of the layer cation,which makes TiO₂ can compound montmorillonite to achieve the support of TiO₂,and it also can make it possible to use special structural characteristics of modified montmorillonite to increase the contact of the catalysts and organic pollutants.Accordingly it can increase the degradation and accelerate the degradation speed.In this article,iron ion doped titanium photocatalyst powders were prepared by FeCl3.The porous natural montmorillonite has been employed as the TiO₂ support.The photocatalytic process of various photocatalysts on methyl orange have been studied.We doped the iron ion in TiO₂,realized the TiO₂ support on the montmorillinte,imprved the photocatalytic activity efficiently,and developed the spectrum respond area to the visible light area.And we can use the solar rays efficiently and reduce the cost.Combine Fe-TiO₂ and montmorillinte carrier,and it is possible to contact catalyst with the degradated material,and develop the degradation effect.In this article,the porous natural montmorillonite have been employed as the TiO₂ supports, and the photocatalytic process of iron doped-TiO₂/montmorillonite on methyl orange(MO)has been studied. The interface mechanism between the TiO₂ and the natural montmorillonite has been discussed,and the change of the kinetic process before and after iron doped-TiO₂ loading has been studied for the first time. The"super reaction area"model has been brought out for liquid system, in order to explain the photocatalytic process of the iron doped-TiO₂/ montmorillonite system.From the AFM,IR and spectra analysis,we can see that a certain amount of iron doped-TiO₂ combined with natural montmorillonite by Ti-O-Si or Ti-O-Al chemical bond.At the initial stage of photocatalytic degra- dation (PCD)of MO,the addition of nature montmorillonite supports have made the initial reaction change from original poor"adsorption controlled"process to the"reaction controlled"process.Since all of the reaction rates of iron doped-TiO₂/ montmorillonite are higher than the pure TiO₂ powder, it's obvious that the montmorillonite supports have enhanced the rate of the slower adsorption process resulting in the increase of the initial reaction rate R0.The first-order reaction rate k1 shows that no matter what kind of process controlled the PCD process at the initial stage the whole process of PCD must be an adsorption controlling process undoubtedly because of the proliferating of the medial product.Iron doped-TiO₂/bentonite composite photocatalyst were perpared by acidity sol-gel method.XRD and IR analysis were used to detect those samples.The photocatalytic properties of the samples which were detected by the decoloration rate of methyl orange solution and COD.It indicated that the photocatalytic properties of this kind of photocatalyst were prominent.The decoloration rate of 20mg/L methyl orange solution at pH=4 and the ratio of Fe-TiO₂/M at 2∶1 under visible hight could reach to 95% with COD more than 84%.Moreover,this catalyst could be reused several times after sintering at 200℃for 2.5h.When using the method of microwave heating, prepared the iron ions doped-TiO₂/montmorillonite composite mineral under the microwave radiation time of 10min, the crystal grain of anatase and rutile are up to the largest,at the same time the account for the crystal phase of anatase is up to the largest,the montmorillonite has a well pillared structure, and the most photocatalytic degradation.When microwave irradiation time is 15min or 20min, the crystalline size of TiO₂ becomes smaller,while the fraction of rutile increase,pillared structure exists, but the photocatalytic performance is not the best;when irradiation time is 5min, the effect of microwave irradiation in accelerating exchange rate and enhancing crystalline decreases, pure TiO₂ is the major in the sample so as to the photocatalytic performance is the best; when irradiation time is 10min,the crystal sizes of TiO₂ are the largest,while anatase is the major,pillared structure exists well, the photocatalytic performance is better, so the microwave irradiation time at 10min is suitable.When the ratio of Fe-TiO₂/M is 2∶1, the ratio of CTAB/M is 2∶5 and the sinter temperature is 450℃, the decoloration can up to more than 98%,the removal of COD can up to more than 82%.Studying the photocatalytic meterial iron ion doped-TiO₂/ montmorillonite composite mineral,has an important reasonal sense and practical sense for the henceforth study of the new type of mineral functional meterial,and also for the resolvation of the pollutant problem with the organic meterial in the water.