活性炭表面含氧官能团对TiO_2/AC的吸附和光催化活性的影响

Effects of surface oxygen functional groups on activated carbon on the adsorption and photocatalytic degradation activities of a TiO_2-AC hybrid for methylene blue and methylene orange

通过硝酸氧化和热处理获得了表面含氧基团和织构显著变化的活性炭,考察了所得活性炭载纳米TiO_2光催化剂(TiO_2/AC)对亚甲蓝和甲基橙的吸附和光催化降解,研究了活性炭表面含氧基团对TiO_2/AC吸附和光催化活性的影响。结果表明,活性炭表面含氧基团的变化比织构显著,其表面含氧基团尤其是羧酸基团对TiO_2/AC的吸附和光催化活性有决定性的影响;同时,针对降解物的电荷性质不同,活性炭表面含氧基团的影响有差异,对阳离子亚甲蓝的吸附和光催化活性的影响比阴离子甲基橙的显著,250℃下脱除表面羧酸后的催化剂对亚甲蓝的光催化活性明显降低而对甲基橙的则稍有增加。

A series of activated carbons(AC)with different amounts of surface oxygen functional groups was obtained by nitric acid oxidation and heat treatment at different temperatures,and these were used as supports for a TiO2photocatalyst.The nature and number of the surface oxygen functional groups were determined by Boehm titration.The pore texture and morphology of the ACs and the TiO2-AC hybrid were characterized by nitrogen adsorption and scanning electron microscopy.The adsorption and photocatalytic activity of the material under ultraviolet light irradiation were investigated using methylene blue(MB,cation dye)and methylene orange(MO,anion dye)as the model compounds.Results show that the oxidation and heat treatment change the surface oxygen functional groups much more than they do the pore texture.The surface oxygen functional groups,especially the surface carboxylic acid,control the adsorption and photocatalytic activities for MB and MO over the TiO2-AC hybrid.The surface oxygen functional groups have a much greater influence on MB degradation than that on MO.The photocatalytic degradation activity for MB decreases at all heat treatment temperatures while that for MO is increased by heat treatment at250C.