Study On Preparation Of Rod-like Mesoporous Titanosilicate Composites With Varied Aspect Ratio, Flower-like Titanate, Flower-like TiO₂, And Their Photocatalytic Performance

In this work, we synthesize rod-shaped mesoporous titanosilicate composites(RMTS) with controllable aspect ratios, flower-like titanate, flower-like TiO2withdominant exposed (101) anatase facets, respectively. And a photocatalytic activity isused to test the photocatalytic activity of the obtained materials. The key points are asfollows:(1) Rod-shaped mesoporous titanosilicate composites (RMTS) with controllableaspect ratios (ARs) are fabricated using tetrabutyl titanate (TBT) and tetraethylorthosilicate (TEOS) as precursors, ammonium hydroxide (NH4OH) as a catalyst, andcetyltrimethylammonium bromide (CTAB) as a template at room temperature with verylow surfactant concentrations under continuous stirring. Results show that slowing thestirring rate or increasing the concentration of CTAB mainly contribute to the growth ofRMTS in the longitudinal direction, resulting in ARs ranging from1to4. But onlystirring can effectively promote growth at AR=5. Moreover, the width of RMTS in thelatitudinal direction can be adjusted in the range of75–120nm by changing the amountof NH4OH used. N2adsorption-desorption isotherms curves of samples show that thesurface area increase with increasing AR. But a high AR value of5(AR5-150-0.5) doesnot result in a corresponding increase in specific surface area, which maybe due tohigher AR values are not conducive to the effective adsorption of N2and othermaterials.A photocatalytic activity test is preformed to photodegradation of p-chlorophenolin an aqueous solution at room temperature under UV light irradiation. When AR is lessthan4, photocatalytic activities of RMTS studies showed that increase with increasedAR. Furthermore, the length of RMTS played a more significant role in increasing itsphotocatalytic activity than its width at lower ARs. RTMS with AR=4and Ti/Si=2(molar ratio) has the highest activity among the nanoparticles obtained likely thatApplication of the composites resulted in nearly97.67%p-chlorophenol degradationunder3h of UV light irradiation.(2) Titanate is widely obtained by post acid treatments with HCl aqueous solutionsafter the hydrothermal process of TiO2without templates in concentrated aqueousNaOH. But the disadvantage of this method is that titanium source is derived from TiO2and has two processes. In this work, flower-like titanate with layered nanosheets is first synthesized by a solvothermal reaction of directly using tetrabutyl titanate as titaniumsource, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol)as stabilizer in acetic acid solution. Scanning electron microscopy (SEM) studies showthat the obtained titanate3D hierarchical flower-like structures assemble by layerednanosheets, and depend on a time-dependent experiment. Trans-mission electronmicroscopy (TEM) studies depict that the layer numbers of each nanosheet vary in therange of6–10, and interlayer distance is about0.83nm. The results from X-raydiffraction (XRD) patterns show that there is no change in phase transition, indicatingthe stable of titanate in the current reaction system. Moreover, the role of P123is foundto be critical in phase and morphology evolution of flower-like structure. There is aweak coordination between two hydrophilic parts of P123and titanium ions on thesurfaces of nanosheet, making P123act as a coating on layered nanosheet. The P123coating provides steric and electrostatic stabilization, which inhibit phase of titanate andfurther form colloidal titanate nanosheets. It is worthy to note that these3D hierarchicalflowerlike structures are sufficiently stable, and calcination at450°C for5h does notchange the integral appearance of the3D flower-like nanostructures and flower-likeTiO2with dominant exposed (101) anatase facets has obtained after calcination. Aphotocatalytic activity test is preformed to photodegradation of p-chlorophenol in anaqueous solution at room temperature under UV light irradiation. When the concerntrateof flower-like TiO2is0.50g L-1and p-chlorophenol is30mg L-1, percent degradation ofp-chlorophenol under3h UV light irradiation is nearly100.00%.