Ag改性石墨相氮化碳(g-C_(3)N_(4))可见光辅助活化过一硫酸盐降解罗丹明B

Visible light assisted peroxymonosulfate activation on Ag modified graphite phase carbon nitride (g-C_(3)N_(4)) for Rhodamine B degradation

采用煅烧法和光还原法制备出具有高活性的Ag/g-C_(3)N_(4)催化剂,并将其应用于可见光下活化过一硫酸盐(PMS)降解罗丹明B(RhB)废水.系统研究了实际因素RhB浓度、催化剂投加量、PMS剂量、pH值和可溶性无机阴离子对RhB降解效果的影响.结果表明,RhB的降解率随着催化剂投加量、PMS浓度的增加而增大,随着初始RhB浓度的增加而减小.弱酸性条件有利于反应活化PMS降解RhB,而中性或碱性条件都会减缓催化反应的进行.Ag/g-C_(3)N_(4)-2/Vis/PMS催化体系30 min内对RhB的去除率最高可达93.2%,分别是Ag/g-C_(3)N_(4)/Vis和单独PMS催化体系的4.0和3.7倍.体系催化活性的提高归因于Ag的表面等离子共振效应及基于硫酸根自由基的高级氧化技术与光催化技术的协同作用.不同阴离子对催化反应的影响不同,溶液中的Cl-会对反应产生轻微的抑制作用,而H2PO-4和HCO^(-)_(3)的出现大大抑制了催化性能.催化剂具有良好的稳定性,5次循环后仍能在30 min之内降解77.4%的RhB.此外,捕获实验和ESR测试结果表明,Ag/g-C_(3)N_(4)-2/Vis/PMS催化体系中存在·O^(-)_(2)、h^(+)、^(1)O_(2)、SO_(4)^(-·)和·OH活性物种,并协同降解RhB污染物.

In this study, Ag/g-C_(3)N_(4) catalysts(Ag/g-C_(3)N_(4)) with high activity were prepared by calcination and photoreduction process. The as-prepared catalysts were studied for the degradation of organic pollutant Rhodamine B(RhB), and were also used for peroxymonosulfate(PMS) activation in the presence and absence of visible light. The effects of RhB concentration, catalyst dosage, PMS concentration, pH value and soluble inorganic anions on RhB degradation were systematically investigated. The results showed that the degradation rate of RhB was positively correlated with catalyst dosage and PMS concentration, but negatively correlated with initial RhB concentration. The optimal pH for the reaction was achieved and weak acidic conditions could promote RhB degradation, while the neutral or basic conditions played negative effects on the reaction. The removal rate of RhB in Ag/g-C_(3)N_(4)-2/Vis/PMS catalyst system was 93.2% within 30 min, which was 4.0 and 3.7 times higher than that of Ag/g-C_(3)N_(4)/Vis and independent PMS catalysis system. The improvement of catalytic activity can be attributed to the surface plasmon resonance effect of Ag and the synergistic effect of advanced oxidation technology based on the sulfate radical and photocatalytic technology. Anions influence experiments showed that different anions played different effects on catalytic reaction. The influence of Cl- on the removal of RhB was insignificant, while H2PO-4 and HCO^(-)_(3) seriously inhibited the degradation. Cycle experiments showed that Ag/g-C_(3)N_(4)-2 catalyst has good stability and 77.4% RhB can be removed within 30 min after 5 cycles. In addition, the capture experiments and ESR tests showed that different active species including ·O^(-)_(2), h^(+), ^(1)O_(2), SO_(4)^(-·) and ·OH can be found in Ag/g-C_(3)N_(4)/Vis/PMS catalyst system, and synergistically degraded RhB pollutants.