碳量子点修饰g-C_(3)N_(4)缓解二苯醚类除草剂污染

Remediation of diphenyl-ether herbicides pollution by g-C_(3)N_(4) modified with carbon quantum dots

为加速二苯醚类除草剂在可见光环境的降解,以玉米芯制碳量子点修饰石墨相氮化碳,合成一种非金属型光催化剂.考察在该催化剂作用下,氟磺胺草醚、三氟羧草醚和乙氧氟草醚等的光解行为及光解前后毒性.结果表明,氟磺胺草醚在可见光照射下的光解速率最大、其次为乙氧氟草醚,光照3 h的降解率即达99%和91%,而三氟羧草醚的光解速率最低、须光照至8 h才能达到90%的降解率.由高斯软件计算NPA(Natural Population Analysis)电荷分布得福井函数和双描述符,预测反应位点并结合液质联用分析降解产物,推测除草剂的降解过程应包括裂解、水解、脱卤、还原和羟基化等,证明了空穴和羟基自由基在其中的作用.观察玉米种子的生长实验,发现氟磺胺草醚的毒性略高于乙氧氟草醚,但二者经光照处理后毒性均显著下降,三氟羧草醚及其光解产物显示为低毒性.

To move faster the visible-light degradation of diphenyl-ether herbicides,the corn cobderived carbon quantum dots were prepared to modify graphitic carbon nitride(g-C3N4)and then achieved a non-metallic photocatalyst.It was well studied with the photolytic behaviors and toxicity alterations on the fomesafen,acifluorfen and oxyfluorfen.The results showed that the degradation rate of fomesafen was the highest and followed by that of oxyfluorfen.They were separately at 99%and 91%after 3 h of visible-light irradiation.And yet the degradation rate of acifluorfen was the lowest and it reached 90%even after lighted by 8 h.Using Gaussian software to calculate the charge distribution of NPA and then the Fukui function and dual descriptors were obtained to predict the reactive sites.The degradation products were analyzed with LC-MS and the photolysis process of herbicides was reasonably speculated such as scission,hydrolysis,dehalogenation,reduction and hydroxylation.The presence of vacancies and hydroxyl radicals was proved great roles in them.It was found that fomesafen performed a slightly higher toxicity than oxyfluorfen during the development of corn seeds while both of them significantly reduced to nontoxic after treatments.Finally,acifluorfen and its photolysis products showed the lowest toxicity among three herbicides.