共聚改性g-C_(3)N_(4)-N可见光催化降解RhB的研究

Photocatalytic Degradation of RhB Dye by Copolymerization Modification g-C_(3)N_(4)-N Under Visible Light

染料废水的排放对人类健康和生态系统构成严重威胁,光催化技术因其操作简单、绿色环保等优点在解决环境污染问题上已显示出巨大的潜力。类石墨相氮化碳(g-C_(3)N_(4)由于成本低且具有良好的化学稳定性,被认为是光催化领域最有前景的新型光催化剂之一,但由于单一g-C3N4的比表面积小、可见光吸收能力低、光生电子-空穴复合率高影响了其光催化性能。以邻氨基苯甲腈和尿素为原料,通过高温共聚改性制备高催化活性的g-C_(3)N_(4)-N光催化剂,研究g-C_(3)N_(4)-N在不同pH值、g-C_(3)N_(4)-N投加量和RhB溶液浓度条件下对RhB光催化降解的影响,并结合红外光谱、XRD、BET、UV-Vis对g-C_(3)N_(4)-N光催化降解RhB的机理和染料降解路径进行解析。结果表明,经共聚改性制备的碳化氮为类石墨型纯相g-C_(3)N_(4)-N,具有稳定的光催化活性、大的比表面积和多孔结构,在初始pH值为3时,加入50 mg的g-C_(3)N_(4)-N在可见光条件下光催化降解10 mg·L^(-1)的RhB可达到最好的光催化降解效果,RhB在暗反应30 min内的吸附去除率可达30%左右,120 min的去除率达到97.7%。在光催化作用下,g-C_(3)N_(4)-N将吸附在光催化剂表面的罗丹明B分子通过快速N^(-)脱乙基过程形成DER、EER和AR等大分子中间体,它们在空穴与·OH和·O2^(-)作用下,共轭结构裂解、开环,生成丁二酸、间苯二酚、丙酸等小分子,脱除的乙基被逐步氧化为乙二醇,这些小分子可以被转化为CO_(2)和H_(2)O。

The discharge of dye wastewater has become a serious threat to human health and the ecosystem.Photocatalytic technology has shown attractive potential in eliminating environmental pollution problems owing to its simple operation and environment-friendly.Graphite-like phase carbon nitride(g-C_(3)N_(4)was considered to be one of the most promising photocatalysts for its low cost and high chemical stability in the field of photocatalysis.However,poor specific surface area,limited optical absorption and high charge carrier recombination rate restricted its photocatalytic efficiency.Thus,a novel graphitic carbon nitride(g-C_(3)N_(4)-N)photocatalyst was synthesized by thermos-induced copolymerization modification method using urea and o-Aminobenzontrile,and its effect on photocatalytic degradation ability of RhB was evaluated based on solution pH value,g-C_(3)N_(4)-N dosage,and RhB concentration.In addition,both the photocatalytic degradation mechanism of RhB and its degradation path by g-C_(3)N_(4)-N were also analyzed through XRD,BET,UV-Vis in this research.The results showed that g-C_(3)N_(4)-N synthesized using copolymerization modification method was pure graphite-like phase g-C_(3)N_(4)-N,with the stable performance of a photocatalytic activity,large specific surface area and porous structure.Under visible light conditions,the photocatalytic degradation efficiency of RhB was found to be optimal with initial pH of 3,RhB concentration of 10 mg·L^(-1) and g-C_(3)N_(4)-N dosage of 50 mg,and the adsorption removal rate of RhB was achieved 30%within 30 minutes in dark reaction.Besides,its photocatalytic degradation removal rate of 120 minutes reach 97.7%.Under the catalysis of visible light,RhB molecules adsorbed on the surface of the g-C_(3)N_(4)-N was firstly degraded into macromolecular intermediates such as DER,EER and AR through rapid N-de-ethylation process,then base on redox reaction of holes,·OH and·O2^(-),conjugated structure of these intermediates was cracked and ring-opened to generate some small molecules,such as succinic acid,resorcinol,and propionic acid,and so on.After that,the removed ethyl groups were gradually oxidized to ethylene glycol.And these small molecules were eventually mineralized into CO_(2) and H_(2)O.