g-C3N4制备及其协同PDS可见光催化降解布洛芬的研究

以尿素为主要原料,采用热聚合法在不同条件下制备了光催化剂g-C3N4(石墨相碳化氮),通过改变尿素在马弗炉中加热的温度(350℃、400℃、450℃、500℃)和时间(0.5 h、1 h、1.5 h),得到不同烧结温度和时间的光催化剂,并对其进行X射线衍射(XRD)、扫描电子显微镜(SEM)、傅立叶红外光谱分析仪(FT-IR)、紫外可见漫反射光(UV-Vis)表征,并通过可见光光催化降解布洛芬试验,探究了制备温度、时间对g-C3N4光催化性能的影响;并在溶液中加入PDS(过硫酸钾),联合g-C3N4在可见光下光催化降解布洛芬。结果表明,当烧结温度为500℃、烧结时间为1.5 h时,制备的g-C3N4在可见光区有较强吸收且具有较大的比表面积,以致其表现出最佳的光催化性能;PDS的存在对布洛芬的降解有促进作用,且加快了g-C3N4对布洛芬的光催化降解,相比于纯g-C3N4,4 h内布洛芬的降解率由63%提升为90.5%。以异丙醇、甲醇、对苯醌、草酸钠、重铬酸钾、甲醇分别为羟基自由基(·OH)、·OH和硫酸根自由基(SO4^-·)、超氧自由基(·O2-)、空穴(h+)、电子(e^-)的捕获剂。通过对反应过程的活性物种鉴定,·OH、SO4^-·、h+、e^-均参与了布洛芬的光催化降解,其中h+在反应中的贡献率达到了82.9%,在降解布洛芬过程中起主导作用;在反应体系中添加PDS后,催化剂g-C3N4的荧光强度变小,即加入PDS能够有效降低g-C3N4的光生空穴与电子的复合率,提高g-C3N4的光催化性能。

Preparation of g-C3N4 and its synergistic PDS visible photocatalytic degradation of ibuprofen

Taking urea as the main original raw material,the present paper has been preparing a photocatalyst g-C3N4(graphite phase nitrogen carbide)by the thermal polymerization under the different conditions by changing the heating urea temperature in the muffle furnace(350℃,400℃,450℃and 500℃)and for the time length of 0.5 h,1 h,1.5 h.And,then,it can be expected to gain the photocatalysts at different sintering temperatures and time lengths by scanning electronic microscope(SEM)subjected to the X-ray diffraction(XRD).And,then,it would be possible for us to characterize the degradation of ibuprofen by visible light through the Fourier infrared spectroscopy analysis(FT-IR)and the UV-visible diffuse reflectance(UV-Vis).And,then,the paper has done an investigation of the effects of the temperature and time on the photocatalytic properties of gC3N4.When the ibuprofen tends to get degraded under the visible light PDS(potassium persulfate),it would be possible for the ions to photocatalyze by adding g-C3N4to the solution.Thus,the results of our testing practice show that,when the sintering temperature is set up at 500℃and the sintering time length is 1.5 h,it would be possible for the prepared g-C3N4to turn to be strongly absorbed by the large specific surface area in the visible light region,which implies that it enjoys the optimistic photocatalytic activity.Such a kind of advantage may account for the presence of PDS,which can promote the degradation of ibuprofen and accelerate the photocatalytic degradation of ibuprofen by gC3N4.In such a condition,the degradation rate of ibuprofen can be made to increase from 63%to 90.5%during a period of 4 h as compared with that of pure g-C3N4.And,if so,the isopropanol,methanol,the p-benzoquinone,the sodium oxalate,the potassium dichromate and the methanol can all be made into the respective catchers of the hydroxyl radical(·OH),·OH and sulfate radical(SO4^-·),the superoxide radical(O2-·),the hole(h^+),and the electron(e^-)·OH,SO4^-·,h^+,e^-,which are all participated in the photocatalytic degradation of ibuprofen.And,all the participated catchers can be identified and determinated by the active species in the reaction process,for the contribution rate of h^+in the reaction can be as high as to reach 82.9%,which is supposed to play a leading role in the ibuprofen degradation.Thus,it can be concluded that,adding PDS to the reaction system can likely reduce the fluorescence intensity of the catalyst g-C3N4,that is to say,the PDS addition can effectively help to reduce the recombination ratio of the photogenerated holes and electrons of g-C3N4 and heighten its photocatalytic performance.