Preparation Of TiO₂/ACF Composite Via Sol-Gel Method And Its Application For Gas Phase Benzene Removal

Indoor air quality has significant influence to human health. Among various VOCs (volatile organic compounds), benzene is one of the most common occurred and carcinogenic. High concentration of benzene concentration would cause seriously health problems. Development of high efficiency benzene removal technology is desired throughout the worldwide.By now, both TiO₂ photocatalysis and activated carbon adsorption are common used methods in VOCs purification. Regarding the advantages and disadvantages of TiO₂ photocatalysis and activated carbon adsorption, if combined together, it maybe become one of the promissing purification technologies for indoor airborne pollutant. Combined theoretical analysis with experimental test, degradation of indoor C₆H₆ by TiO₂/ACF composite materials obtained by sol-gel method. Experiment parameters influence the benzene removal performance of TiO₂/ACF was systematically investigated, and the scanning electron microscope (SEM) and X-ray Diffraction (XRD) characterization and activity evaluation of the catalysts were also performed. Identification the intermediate products of benzene degradation was conducted. The relative removal mechanism of benzene over TiO₂/ACF composite material was elucidated. The results showed as follows:1. When the initial concentration of benzene were 5853 mg/m³, 2926.5mg/m³, 585.34mg/m³, with the increase of initial concentration, Photocatalytic efficiency reduce. It was also found that the Photocatalytic degradation ineffective to 5853 mg/m³ of benzene after 60min, which is what catalyst deactivation phenomena.2. Circulation flow rate for different micro-pump found that the gas flow cycle little effect on the rate of benzene photocatalytic degradation.3. When the percentage of TiO₂ load ACF from 31.57% to 47.29%, the photocatalytic activity increased slightly, from 37.67% to 39.53%. With the increase of loaded times, Photocatalytic degradation rate increased again emerged the volatility relations, first decrease and then increase which is likely that at first TiO₂ particles increase lead to the photocatalytic degradation rate increase, after increase the load content, resulting in the increased photocatalytic reactin of actived sites, but there is no catalyst surface area increases, making photocatalytic degradation experiments act as a catalyst loading of the part and not in proportion. When the content of 47.29%, the best photocatalytic effect. Supported catalysts show that photocatalytic degradation of activity: 2> 1> 5> 4> 3 times.4. At the different temperatures (300-800℃), the specific surface area show that decrease following the the temperature increase, the sample surface area decreased in the relatively flat, but 400℃after the sharp decline, resulting in the catalyst can provide actived sites a drastic reduction , and affect the absorption of catalyst, At the end lead to the TiO₂/ACF composite materials reduce the benzene removal. At 400℃heat treatment of samples remove benzene has the best effect.5. SEM characterization revealed that the load 1 time, TiO₂ in the ACF thin layer formed on the surface of integrity, as the load increased, TiO₂ thin thickening, cracking, and even some loss, Effective illumination to accept gas photocatalytic reaction TiO₂ thin layer of TiO₂/ACF reduced . XRD analysis showed that the composite material in TiO₂, at 300℃, samples of TiO₂ basically amorphous structure exists, the temperature rose to 400℃began to generate anatase, 500℃-600℃anatase diffraction peaks become more obvious and acute , when the temperature rose to 700℃, rutile structure began to generation, to 800℃temperature, the majority of its crystal into rutile.6. TiO₂ and the synergies between the ACF. TiO₂/ACF in ultraviolet light as 1 h after the removal of benzene to 39.53 %, Pure TiO₂ remove benzene showed the degradation of rate was 27.65 %, TiO₂ was loaded on the ACF, the catalytic performance is the original 1.43 times, Between the TiO₂ and the ACF exist the synergies enhance the performance of the removal of benzene.7. The intermediary product carries on the analysis using GC-MS to the benzene elimination process, by comparing the response to 60 min before and after the catalyst deactivation intermediate product types, discovered that is mainly some macro-molecule alkane production, and breaks without enough time degradation into CO₂ and H₂O, gathers in the TiO₂ surface and occupies the TiO₂ photocatalyst surface activity position, thus causes the TiO₂ deactivation.