The Study On Quenching Of Residual H₂O₂ From UV/H₂O₂ Process By Granular Activated Carbon

As an advanced oxidation technology,UV hydrogen peroxide（UV/H₂O₂）had broad application prospects in the advanced treatment process of drinking water due to its strong oxidation capacity,small footprint,and low temperature impact.But UV/H₂O₂ Excess H₂O₂was produced in the process,which affects human health.In view of this,the granular activated carbon（GAC）quenching H₂O₂ process could be used as a post-process of UV H₂O₂ becauseof its excllent removal effect and no pollutant generation.In this paper,the kinetics of GAC quenching H₂O₂ was studied.Several influencing factors in the quenching process were analyzed and the mechanism was studied.The main conclusions were as follows:First,a static experiment of GAC quenching H₂O₂ was performed.the effects of H₂O₂initial concentration,GAC dosage,solution temperature,solution pH,different anions and natural organic compounds（NOM）on the quenching of H₂O₂ by GAC were investigated.（1）The kinetic analysis of the reaction process of GAC quenching H₂O₂ was carried out.The results show that the GAC quenching H₂O₂ reaction process accords with the pseudo first-order reaction kinetics.（2）The experiment used 8-16 mg/L H₂O₂ as the test object.After 35 min,the removal rate was maintained at about 50%.By analyzing the k value of each reaction rate constant,it is known that the change of the initial concentration of H₂O₂ is almost no for the k value.The effect is that the k value is 0.01285±0.0003 min^-1 at each initial concentration.（3）The experiment was carried out with H₂O₂ under the action of 0.1-0.9 gGAC.After 35 min,the removal rate increased from 28.12%to 68.75%.By analyzing the k values,k value(0.0016-0.0149min^-1)The linear increase increases with the increase in the amount of GAC（0.1-0.9 g）,and the rate of increase is 0.016 min^-1·g^-1.（4）The experiment was carried out with H₂O₂ under the temperature of 5-25°C.After 35 min,the removal rate increased from 31.25%to 77.50%,and the analysis of each k value(0.0089-0.0188 min^-1)and The Lenius formula shows that the increase of temperature which improves the quenching efficiency of GAC in the reaction.The activation energy required during quenching is Ea=84.26kJ·moL^-1.（5）The experiment was carried out with H₂O₂ at pH=4.5-9.5.After 35min,the removal rate increased from 27.50%to58.13%.According to the analysis of each k value(0.0072-0.0176 min^-1),GAC The quenching efficiency increases with increasing pH.（6）H₂O₂ under different anions and natural organic matter（NOM）was used as the test object.After 35 minutes,the removal rate of each group was HCO₃^->blank group>Cl^->SO₄^2->NO₃^->NOM,by analyzing the k values,HCO₃^-can promote the reaction of GAC quenching H₂O₂,while other ions will be The GAC quenching process of H₂O₂ has an inhibitory effect,and its inhibition ability was NO₃^->SO₄^2->Cl^-,and NOM-inhibition of GAC quenching H₂O₂.In the dynamic experiment,all the reactions occurred in the fast small carbon column test（RSSCT）.The removal of H₂O₂ in the blank group,NOM added group and HCO₃^-added group was compared and analyzed.（1）After 25 days of reaction,the carbon column The removal rate of H₂O₂ in the GAC was gradually reduced to 5%and remained unchanged until the end of the test,indicating that the GAC gradually appeared adsorption saturation during the entire carbon column test.（2）After 21 days,the NOM carbon column was added.The GAC will appear saturated until the end of the test,indicating that the addition of NOM will accelerate the saturation of the GAC in the carbon column.（3）After 29 days,the addition of the GAC in the HCO₃^-carbon column will result in saturation until the end of the test,indicating that HCO₃^-addition will slow the saturation of the GAC in the carbon column.For the GAC after the static and dynamic experiments have been completed,relevant characterization experiments were carried out.（1）Infrared spectroscopy and Boehm titration were performed on GACs at different pHs（pH=5.5,pH=7.5,pH=9.5）.The experimental results show that the pH of the solution will affect the state of H₂O₂ in the solution and the surface functional groups of the GAC.At pH=4.5-7.5,the H₂O₂ in the solution will be stable,the acidic functional group will appear on the surface of the GAC,and the acidic functional group will inhibit the solution.Quenching of H₂O₂.With the increase of pH,H₂O₂ in the solution is more easily dissociated into·OH and OH-when pH=7.5-9.5,while the acidic functional groups on the surface of GAC will gradually decrease and the surface basic functional groups will gradually increase.Basic functional groups The quenching of H₂O₂ in the solution will be accelerated.（2）The surface morphology changes of the GAC（blank group GAC,HCO₃^-group GAC,NOM group GAC）and the original GAC that have completed the RSSCT penetration test were tested.The experimental results show that the original GAC surface has stripe protrusions and is relatively rough.Although the roughness is constant during the reaction of H₂O₂,its strip-like protrusions are eliminated and a large number of holes are formed.The surface of the GAC to which NOM is added is relatively smooth but the pores are relatively small,and the surface of the GAC to which HCO₃^-is added becomes smooth and The holes are relatively large and pass through the interior of the GAC.（3）For the determination of the specific surface area and pore volume of each GAC and the original GAC in the breakthrough experiment,the experimental results show that the specific surface area of the GAC after the reaction has decreased to some extent,and the GAC will react with H₂O₂.There are microporous holes produced.The reason why there are not many pores in the NOMgroupis that the addition of NOM blocks the surface micropores of the GAC,and the addition of HCO₃^-causes a large number of microporous pores on the surface of the GAC.The pore volume of the pores accounts for the total pore volume ratio V HCO3-GAC>V blank GAC>VNOMGAC>V original GAC.Through the related research,the paper deepens the understanding of the degradation kinetics of target H2O2,and provides theoretical data and certain guidance for strengthening the performance of GAC quenching residual H2O2 in water and promoting its practical application.It helps UV/H2O2 process in drinking water.Further promotion in the processing industry.