摘要
In the present study,zinc molybdate(β‐ZnMoO4)and graphitic carbon nitride(g‐C3N4)‐modifiedβ‐ZnMoO4(β‐ZnMoO4/g‐C3N4)were prepared to decontaminate aqueous solutions from the antibiotic sulfamethazine(SMZ).Our results revealed that the hydrothermal synthesis method greatly influenced the photocatalytic activity of the resultant catalysts.The pristineβ‐ZnMoO4samples obtained under more intensive synthesis conditions(24h at280°C)showed higher photocatalytic activity than that prepared for12h at180°C(denotedβ‐ZnMoO4‐180).In the case of in situ hydrothermal synthesis ofβ‐ZnMoO4/g‐C3N4,a surface‐modified sample was only obtained under the reaction conditions of180°C for12h.Compared with the sheet‐likeβ‐ZnMoO4‐180sample,theβ‐ZnMoO4‐180/g‐C3N4composite showed enhanced photocatalytic activity for the degradation of SMZ.By contrast,the hydrothermal reaction at280°C caused the gradual decomposition of g‐C3N4.It is believed that the structural incorporation of g‐C3N4intoβ‐ZnMoO4at280°C might disrupt the crystal growth,thereby deteriorating the performance of the composite catalysts formed at this temperature.For the composite catalysts prepared by the ultrasonic method,a remarkable increase in the degradation rate of SMZ was only observed at a high g‐C3N4content of8mol%.The photocatalytic degradation of SMZ byβ‐ZnMoO4‐180/g‐C3N4composite catalysts followed pseudo‐first‐order kinetics.Further study of the photocatalytic mechanism revealed that holes and superoxide radicals were the dominant oxidative species in the photodegradation process.The enhanced photocatalytic performance of the composites was attributed to the higher separation efficiency of the photogenerated electron‐hole pairs at heterogeneous junctions.The degradation intermediates of SMZ were detected by liquid chromatography‐mass spectrometry,from which plausible reaction pathways for the photodegradation of SMZ were proposed.Our results indicated that the synthesis method for g‐C3N4compos
在过去几十年中,钼酸盐在功能材料领域的应用备受关注.例如,半导体材料二价金属钼酸盐MMoO_4(M=Ca,Mg,Zn)在发光、催化、电容器、闪烁探测器等方面已有良好的应用.研究表明,钼酸锌在紫外或可见光照射下能够有效降解甲基橙、维多利亚蓝、苯酚等污染物.中国拥有丰富的钼资源,目前钼主要用于生产高强度钢.制备钼基高效除污除材料可作为钼资源的另一种高附加值利用模式.氮化碳(g-C_3N_4)作为一种低成本的光活性改性剂,可提高半导体材料的光催化性能.迄今为止,基于氮化碳复合材料的制备方法包括:原位水热合成、超声波复合、一步升温合成和沉淀法等.然而,很少讨论合成方法对复合材料性能的影响.本文以β-ZnMoO_4为主体材料,g-C_3N_4为修饰材料,首次制备了两者复合的新型光催化剂.采用不同的方法和条件制备了β-ZnMoO_4和β-ZnMoO_4/C_3N_4复合材料,探讨了合成方法对复合材料光催化性能的影响,并进一步研究了材料光催化降解磺胺二甲嘧啶的动力学和降解途径.以钼酸钠和硝酸锌为原料,在不同温度和时间条件下,采用水热法合成得到了两种不同形貌的β-ZnMoO_4材料.光催化降解实验结果显示,水热合成条件对催化剂的光催化活性影响很大,280℃水热条件下维持24 h,得到表面光滑的不规则微米颗粒(β-ZnMoO_4-280),其光催化活性高于180℃条件下获得的片状形貌的钼酸锌材料(β-ZnMoO_4-180).β-ZnMoO_4/C_3N_4复合材料通过原位水热法和超声法合成,结果显示,原位水热合成条件下获得的β-ZnMoO_4-180/C_3N_4光催化剂对磺胺二甲嘧啶表现出显著增强的降解能力.相比之下,在280℃水热条件下,C_3N_4颗粒发生逐步分解,且反应开始时C_3N_4颗粒会扰乱β-ZnMoO_4-280晶体生长的连续性,使复合材料性能下降.对于超声法合成的β-ZnMoO_4/C_3N_4材料,两种β-ZnMoO_4/C_3N_4复合材料的光催化活性均提高,但
基金
supported by the National Natural Science Foundation of China(51778505)
the grants from Hubei Province of China(Special Grant for Technological Innovation(2016ACA162)
the Natural Science Foundation,2015CFA017)~~
