Investigation Of TiO₂-rGO/ASC Photocatalysts For Flue Gas NO Removal

Atmospheric pollutant,mainly comprised of sulfur dioxide (SO2) and nitrogen oxides (NOx), is partly orginating from extensive power plant.Especially NOx have provoked urgent environmental stress and human health problem with the formation of acid rain,haze,photochemical smog and the deleption of ozone layer. Owing to using existing water and oxygen within flue gas as reactants,the photocatalytic oxidation technology could improved "water intoxication" of activated semicoke,together with reinforcement of oxidizing NO by generating active radicals.Along with diversified photocatalysts, the TiO2-based materials were probably the most suitable for NO abatement due to its non-poisonous, anti-photocorrosive and inexpensive properties. However, the quick recombination of photon-generated carriers and poor visible light response from optical perspective together with the unideal mechanical properties and lower specific surface area from denitration catalyst perspective left much to be desired.Therefore, the paper focused on exploration of easy preparation,low cost,water-resistant and activated semicoke based phocatalysts with visible light response.The principal research work was as following:In the present work, activated semi-coke supported TiO2-rGO nanocomposite photocatalysts(TiO2-rGO/ASC) were synthesized through one-step, green solvothermal method with different content of reduce graphene oxide. Detailed structural information was characterized by SEM,EDX,XRD,UV-Vis DRS and PL.Results indicated that TiO2 with small size and good crystality were evenly dispersed on rGO in TiO2-rGO/ASC photocatalysts. TiO2 in situ growing on rGO layers would lead to hold back quick recombination of charge carriers and redshift of absorption bands.Effect of TiO2 and rGO content on NO conversion over TiO2-rGO/ASC photocatalysts under UV irradiation was investigated.Results showed that photocatalytic activity increased up to 67.74% with the enhancement of TiO2 content ranging from 0.5% to 1.0%,while the NO conversion would decrease with the continue enhancement of TiO2. It turned out that the NO conversion was promoted with the increase of rGO content and TiO2-8%wt rGO/ASC photocatalysts showed the best photocatalytic performance with 70.68% NO conversion.Given that light,oxygen content and relative humidity were key factors for photocatalytic activity,corresponding pulse experiment was devised to comfirm the process of photocatalytic removal of NO.The results showed that comparing to the influence of light,oxygen content exhibited superior impact on photocatalytic performance.The NO conversion showed a steady and then decline trendy in absence of water.It was implied that the process of photocatalytic removal of NO was comprised of photocatalitic oxidation and normal oxidation.Effect of TiO2 and rGO content on NO conversion over TiO2-rGO/ASC photocatalysts under visible light irradiation was investigated.lt turned out that The NO conversion was promoted with the increase of rGO content and TiO2-8%wt rGO/ASC photocatalysts showed the best photocatalytic performance with 53.3% NO conversion. lower recombination rate of photogenerated charge and slight red shift of absorption bands were responsible for improved photocatalystic activity.Besides,the inverse correlation of generating CO concentrate and NO conversion indicated the competitive reaction.Finally, optimization of operational parameters with 70℃,8% O2 and 8% relative humidity were also obtained. Deactivation of TiO2-rGO/ASC photocatalysts for NO removal was investigated. Four different regeneration methods, comprised of thermal regeneration, ultrasonic water rinse, ultrasonic ammonia rinse and thermal vapor regeneration were carried out. The accumulation of nitrate on photocatalysts surface confirmed by FT-IR analysis was responsible for the deactivation of photocatalytic activity under four hours duration. It was worthy to note that thermal vapor regeneration would be optimal method owing to its excellent regenerative capacity and inexpensive procedure and the descent of NO conversion with the increase of generation times stagnates after third time regeneration.