g-C3N4/TiO2/SiO2纳米复合介孔材料光催化降解微囊藻毒素

Many drinking water sources have been seriously contaminated by microcystins (MCs) in our country. The difficult problem confronted by the people working in the fields of correlative scientific research is how to highly effectively remove MCs from water. In this project, novel g-C3N4/TiO2/SiO2 nanocomposites possessing ordered mesopore channels (including grains and membranes) are scheduled to prepare using the applicant et al. improved “evaporation-induced self-assembly” approach combined with the removal of templates in the mesochannels by calcination, crystallization of pore-walls (including the formation of anatase TiO2 and g-C3N4) under high temperatures and then removal of carbon under mild conditions. The ordered mesoporous g-C3N4/TiO2/SiO2 nanocomposites, with very unique mesoporous frameworks consisted of g-C3N4 (graphitic carbon nitride) nanoparticles, anatase TiO2 nanocrystals and amorphous SiO2 nanoparticles by linking mutually, integrate “g-C3N4/TiO2” with high degradation activity under visible light, SiO2 with excellent adsorption performance, large number of strong acid sites allowing effective hole-trapping and then prohibiting undesirable photocarrier recombination, high specific surface areas and mesochannels into one, which can fast and highly effectively remove MCs from water by synergistic role. The influences of various preparation conditions on the mesoporous structures, physicochemical properties, etc. of the above-mentioned materials are scheduled to study systematically. The synthesis mechanisms, and the laws of adjusting and controlling will be clarified. The relationship between the performances of adsorption and photocatalytic degradation of MCs and the compositions, structures and surface properties, etc. of the mesoporous photocatalysts prepared with various g-C3N4/TiO2/SiO2 molar ratios under different crystallization conditions are planned to study detailedly, in order to elucidate their intrinsic correlations and obtain the optimal photocatalysts (including grains and membranes). The degradation intermediates and products of MCs, and their sorts and structures are planned to study deeply in order to clarify the photocatalytic degradation mechanisms. At present, the research in this aspect has not been seen in the literature.

我国大量饮用水源被微囊藻毒素(MCs)严重污染，如何高效去除MCs是相关科研面临的难题。本项目拟采用申请者改进的“溶剂挥发诱导的自组装”法与焙烧去除模板剂、高温孔壁晶化、温和除碳相结合，研制新颖的g-C3N4/TiO2/SiO2纳米复合有序介孔材料(颗粒、膜)。该材料由g-C3N4(石墨相)纳米颗粒、锐钛矿TiO2纳米晶粒与SiO2纳米颗粒相互连接组成，集可见光降解活性高的“g-C3N4/TiO2”、吸附性能优良的SiO2、有效分离光生空穴的强酸中心、大比表面积、介孔道于一身、协同作用，可高效去除水中MCs。系统研究各种制备条件对上述材料的介孔结构、物化性质等的影响，阐明合成机制与调控规律。详细研究各种催化剂组成、结构、物化性质等与吸附和光催化降解MCs性能的关系，阐明其内在联系，并研制出性能最佳光催化剂。深入研究MCs降解中间物、产物及其种类和结构，阐明降解机理。目前这项研究尚未见报道。

我国大量饮用水源被微囊藻毒素(MCs)严重污染，如何高效去除MCs是相关科研面临的难题。本项目先用“同步组装”法合成两维六方结构锐钛矿TiO2-SiO2纳米复合有序介孔材料(母体)，然后用“抽提SiO2”法，在孔壁上制备“二次孔”，获得三维高度互通的锐钛矿TiO2-SiO2纳米复合介孔材料和锐钛矿TiO2介孔材料。本研究的策略是采用高含量二氧化硅、高晶化温度以及温和抽提法。结果表明，均一的二次孔可在3.6–6.2 nm范围内精细调控，但介孔骨架结构仍保持原有的规整性和完整性。该方法简单、温和、可控、易重复。MC-LR在三维介孔TiO2内的扩散效率显著高于在其母体内的效率。介孔TiO2对MC-LR展现出很好的光催化降解(λ=254 nm)性能，该性能分别是其母体和P25光催化剂的8.8和13.4倍。此外，出人意料的是，介孔TiO2降解偶氮染料酸红1和活性艳红X3B的活性极高，该活性分别是P25的55.9和51.1倍，甚至分别高达其母体的87.0和84.7倍。研究证明，“大孔径二次孔”对活性的巨大升高起了关键作用，而大比表面积也有较大贡献。三维复合介孔光催化剂对亚甲基蓝的降解速率相当高，该速率是其母体的7.3倍，甚至高达P25的38.8倍。大孔径二次孔在活性提升中起压倒性作用，而匹配的吸附性能起了重要的协同作用。同样重要的是，上述催化剂均具有相当的稳定性和可重复使用性。上述结果在当时的文献中均未见报道。这项研究为合理设计和制备具有三维大孔径二次孔和超预期光催化性能的其它介孔材料开辟了一条崭新途径。 .采用“多组分协同组装”法与“热缩聚、模板剂去除、高温孔壁晶化、温和除碳”等过程相结合，成功合成出各种摩尔比、新颖的两维六方结构xg-C3N4/yTiO2/zSiO2纳米复合有序介孔材料。采用SAXS、SAXRD、WAXRD、TEM、EDX、Mapping、电子衍射、低温氮吸附、UV-vis DRS等技术对制备的样品进行了详细表征。在模拟太阳光照射下，分别评价了上述样品吸附与光催化降解MC-LR和RhB的性能。令人鼓舞的是，一些催化剂的活性相当高。同样，催化剂将CO2还原为CO和CH4的性能也非常好，CO的产率很高。系统研究了光催化剂的合成条件及其物化性质等对其吸附与光催化性能的影响。