Preparation And Properties Of Photocatalyst Of Nanocrystalline TiO₂-Pillared Montmorillonite

TiO₂ pillared montmorillonite combinated with the photocatalytic activity of TiO₂ and the high adsorption properties of montmorillonite,as a novel environmental material,has been one of the hot research topics and attracted much attention domestically and internally.However,for the traditional preparation route of TiO₂ pillared montmorillonite,the precursor of TiO₂(titanium gel) is too small to transform into the anatase TiO₂ crystals with an appropriate size.Thus,photocatalytic activity is limited. The microstructure of pore size and volume in montmorillonite plays a key role in the transportation efficiency of organic contaminants with large molecular weight.Therefore,how to optimize the interlayer distance of montmorillonite and how to control the size of TiO₂ crystals with the improvement of photocatalytic activity become an important challenge.In this paper,a new TiO₂ pillared montmorillonite different from traditional pillared method was suggested.Firstly,TiO₂ nanoparticle was prepared and size control with application of DEA as modified and structural regular;Secondly,surfactant CTAB was introduced into DEA-TiO₂ suspension for assemblying a novel pillar of "DEA-TiO₂-CTAB",which was intercalated with montmorillonite.Firstly,Nanosized titania dioxide particles were prepared by controlling the hydrolysis of TiCl₄ in aqueous solution with further amine modification.The effects of the process parameters(concentration of Ti⁴⁺, acidity,hydrolysis temperature,Ti/diethanolamine(DEA) ratio) have been investigated in terms of structural phase and particle size.The systematic study of the process parameters allowed to optimize the synthesis conditions and to identify a concentration of titanium ions Ti⁴⁺ into the aqueous solution in the range between 0.75 to 1.5m/L,a Ti⁴⁺/H⁺ ratio of 2/1 to 2/3,a hydrolysis temperature of 70-95℃and a Ti/diethanolamine(DEA) ratio of 1/1 as optimum conditions.The optimization of the process parameters led to single phase rutile nanospheres and mixed crystalloid of anatase and rutile with average dimension of 4-10 nm.Secondly,we pillared montmorillonite with the prepared DEA-TiO₂ nanoparticles,and in order to overcome the lack of single TiO₂ pillared clays,use CTAB(Cetyltrimethylammonium bromide) as the microstructural modifier in the synthetic procedure.Three kinds of Ti/CTAB pillared clays were synthesized by controlling the addition sequences.The well-designed experiments show that the reaction(TCM) with DEA-TiO₂ and CTAB combined first,and then pillared montmorillonite led to the optimal results.The interlayer distance reaches 2.04 nm.After calcinations,interlayer distance of TCM-500 reaches 1.29 nm.This strategy can improve the pore diameter,structure of montmorillonite.At last,we use the so-called composite materials were applied into the decomposition of methyl orange and investigate their photocatalytic activity.The investigation show that the surfactant improves the content of montmorillonite and improves the photocatalytic activity.The adsorption ratios of TCM,CMT and TCM are similar,which are all around 87%.But the single DEA- TiO₂ pillared clays is 78%,and montmorillonite is only 8.42%.The influence of calcination is not very evidence.In the photocatalytic experiment,we compare TCM and TCM-500 with commercial P25.The photocatalytic ratios of these three kinds of photocatalysts are similer,TCM-500 is better than P25 appreciably,which reaches 99.64%.It is showed that the strategy can better combine the photocatalytic activity of TiO₂ and the high adsorption properties of montmorillonite.