UV/H_(2)O_(2)降解罗丹明B综合实验设计

Comprehensive experimental design on UV/H_(2)O_(2)degradation of Rhodamine B

该文设计了利用UV/H_(2)O_(2)工艺降解染料废水中有机污染物罗丹明B(Rhodamine B,RhB)的综合实验,并采用单因素实验和响应曲面法优化实验条件。实验结果表明UV/H_(2)O_(2)工艺降解RhB过程符合假一级动力学方程,H_(2)O_(2)投加量和紫外光强度的交互作用是降解RhB最显著的影响因素。当H_(2)O_(2)的投加量为47.45 mL/L、水体初始pH值为8.11、紫外光强度为730μW/cm^(2)时,反应120 min后,RhB的理论去除率为92.44%,与验证实验结果的相对偏差为0.89%。由紫外-可见光谱和三维荧光光谱扫描结果可知,RhB在反应过程中被有效降解。该实验利用两种实验方法优化工艺条件,有助于提高学生在科研训练中对反应影响因素、动力学拟合及实验条件优化的认识。

[Objective]Rhodamine B(RhB)is a typical triphenylmethane dye with a carboxyl structure and a type of recalcitrant organic pollutant.It can cause significant damage to human health and the environment when discharged into water bodies.Ultraviolet/hydrogen peroxide(UV/H_(2)O_(2))technology uses UV light excitation to decompose H_(2)O_(2)into hydroxyl radicals(•OH)with strong oxidizing properties.The standard electrode potential of•OH is 2.8 eV,which is much higher than those of ordinary oxidants such as O3,Cl2,and H_(2)O_(2).UV/H_(2)O_(2)technology has the advantages of rapid reaction,low selectivity with organic compounds,and good treatment effects.In addition,the hydrolysis products of H_(2)O_(2)are water and oxygen,which are environmentally friendly and do not cause secondary pollution.Therefore,among many advanced oxidation methods,UV/H_(2)O_(2)technology is receiving widespread attention and research.Herein,a comprehensive experiment was designed to degrade RhB by the UV/H_(2)O_(2)process.[Method]The effects of process conditions such as H_(2)O_(2)dosage,pH value,and UV light intensity on the removal efficiency of RhB by UV/H_(2)O_(2)were explored by single-factor experiments.Response surface methodology(RSM)was employed to examine the interaction of the different influencing factors.A quadratic regression model for the RhB removal rate was constructed,and its accuracy was verified through experiments.UV-Visible(UV-Vis)spectroscopy and three-dimensional fluorescence spectroscopy were applied to confirm the removal effect of RhB.[Results]The results of the single-factor experiments indicated that the degradation process of RhB by UV/H_(2)O_(2)followed the pseudo-first-order kinetic equation.Properly increasing the concentration of H_(2)O_(2)improved the reaction rate and the degradation effect of RhB,but its excessive addition led to the self-loss of•OH.Weak alkaline conditions were more conducive to RhB degradation in UV/H_(2)O_(2)systems.With the increased UV light intensity,the reaction rate constant k value significantly increased.The RSM results revealed that the interaction between H_(2)O_(2)dosage and UV light intensity significantly affected RhB degradation.At a H_(2)O_(2)dosage of 47.45 mL/L,the pH value was 8.11,the UV light intensity was 730μW/cm^(2),and the RhB removal rate could reach 92.44%after 120 min.The relative deviation between the experimental and predicted values of the model was 0.89%.The predicted values from the regression model established with Design-expert software were highly correlated with the experimental values,accurately reflecting the actual removal of RhB.The UV-Vis and three-dimensional fluorescence results showed that a large number of azo bonds were rapidly broken by the active components,and the polycyclic aromatic hydrocarbons in the molecular structure of RhB were disrupted,but some benzene derivatives were formed during the reaction.[Conclusions]The UV/H_(2)O_(2)method could effectively degrade RhB dye wastewater.Single-factor experiments and RSM were used to optimize the conditions of the UV/H_(2)O_(2)process,which helped improve students’understanding of the influencing factors of the reaction,kinetic fitting and optimization of experimental conditions in scientific research training,and cultivating students’scientific and rigorous style.