Ag/Zn改性桑叶生物质碳及其光催化降解染料性能

Study on Ag/Zn modification of mulberry leaf biomass carbon and its photocatalytic degradation of dye

通过在桑叶表面原位生长Zn基有机金属框架材料ZIF-8,再通过Ag改性、热解,制得一种新型的双金属Ag/Zn改性桑叶生物质碳材料(Ag/Zn@CL)。采用扫描电镜、X射线衍射、X射线光电子能谱、N_(2)吸附-脱附、紫外可见漫反射等手段对Ag/Zn@CL的组成与形貌结构进行了分析表征,并在可见光照射下研究了该材料对于有机染料结晶紫(CV)的光催化降解性能,分析了光催化脱色机理。实验结果表明,金属Ag成功负载在了ZIF-8复合桑叶的表面,制得的Ag/Zn@CL具有较窄的带隙能(2.71 eV),在可见光照射下可以产生大量e^(-)并进行后续的自由基反应,表现出优异的光催化降解活性。通过对桑叶与ZIF-8质量比、Ag的添加量、焙烧温度、焙烧时间等条件优化后,当CV初始质量浓度为300 mg/L,添加20 mg AgNO_(3),桑叶与硝酸锌质量比为1∶2,600℃下碳化3 h,暗反应30 min,光反应1 h后,CV的脱除率可达到97%。经过5次吸附-光催化循环测试,该材料对CV的降解率能保持在80%左右。利用废弃桑叶制得的Ag/Zn@CL能够快速、高效降解水体中的有机染料,同时具有较好的循环稳定性,在有机废水处理领域具有广泛的应用前景。

In the present study,a novel bimetallic Ag/Zn-modified biomass carbon material for mulberry leaves(Ag/Zn@CL) was successfully prepared.The material was prepared by in-situ growth of Zn-MOF(ZIF-8) on the surface of mulberry leaves and then Ag modification and heat treatment.The composition and morphology of Ag/Zn@CL were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),N_(2) adsorption and desorption,and UV-Vis diffuse reflection.The photocatalytic degradation of organic contaminant dye crystal violet(CV) by Ag/Zn@CL under visible light was further investigated,and its degradation mechanism and core were analyzed.The experimental results showed that Ag was successfully loaded on the surface of ZIF-8 composite leaves,and the prepared Ag/Zn@CL had a narrow band gap energy(2.71 eV),which could generate a large number of electrons under light conditions,and then carry out the subsequent free radical reaction,showing excellent photocatalytic degradation activity.According to the optimization of the ratio of mulberry leaves to ZIF-8,Ag addition amount,baking temperature and time,when the initial mass concentration of CV was 300 mg/L and 20 mg AgNO_(3) was added,Ag/Zn@CL was carbonized at 600 ℃ for 3 h,dark reaction for 30 min,and light reaction for 1 h,the removal rate of CV can reach 97%.After 5 cycles of adsorption-photocatalytic test,the degradation rate of CV was maintained at about 80%.Ag/Zn@CL prepared from waste mulberry leaves can degrade organic dyes in water quickly and efficiently,and had good cycle stability,which has a wide application prospect in the field of organic wastewater treatment.This research provided a new idea for the rational utilization of waste biomass resources,and also laid a foundation for the application of photocatalysis technology in the field of environmental protection.In conclusion,in this study,a new bimetallic Ag/Zn@CL photocatalytic material was prepared by in-situ growth of Zn-MOF(ZIF-8) and modification by Ag,and its degradation performance of organic dye CV was investigated,and its degradation mechanism was analyzed.The experimental results showed that Ag/Zn@CL had good photocatalytic degradation performance and cyclic stability,which provided a new solution for the treatment of organic wastewater.In the future study,we will continue to optimize the preparation conditions of Ag/Zn@CL to further improve its application effect in the field of environmental protection.At the same time,attention will also be paid to other types of photocatalytic materials to provide more possibilities for water pollution treatment.