Research On Preparation Of Doped Cyanobacteria Carbon And Degradation Of Orange Ⅱ In Wastewater By Activated Persulfate

The water quality of the lake is far from the target requirements,and cyanobacteria still erupt every year.The domestic cyanobacteria lake is usually made into algae cake for landfill after salvage,without large-scale resource utilization.As a cheap,easily available and high-yield biomass material,cyanobacteria is a good choice of biological carbon source.In this paper,based on the advanced oxidation technology of persulfate,cyanobacteria were selected as biomass materials to prepare cyanobacteria carbon.The environment-friendly activated persulfate materials were prepared by high-temperature carbonization and liquid-phase reduction,and nitrogen doped cyanobacteria carbon（N@ACC）and cyanobacteria carbon loaded zero valent iron（NZVI@ACC）.The degradation effect,influencing factors and degradation mechanism of two kinds of materials on orange II（OII）were studied.The main research contents and conclusions were as follows:（1）Nitrogen doped cyanobacteria carbon materials were prepared at high temperature with cyanobacteria carbon as carrier and urea as nitrogen source（N@ACC）,the material had a larger specific surface area（159.12 m2/g）and smaller average particle size（3.28 nm）,and there were a lot of functional groups on N@ACC surface,which was conducive to the reaction of activated materials in aqueous solution.Researched the effect of N@ACC/PMS system degrade OII and explored the influencing factors.The results showed that the nitrogen doped material had a significant effect on activated persulfate,and when the initial p H of 100 mg/L OII was6 and the reaction temperature was 25 ^oC,N@ACC under the conditions of 2 g/L and0.56 g/L PMS dosage,the degradation rate reached 98.80%after 35min reaction.The results of inhibition experiment and free radical capture showed that the free radicals that played a role in the reaction process were·OH,SO₄^-,¹O₂,in which singlet oxygen played a major role.Pyridine Nitrogen at the N@ACC edge could be used as Lewis basic reaction site to induce the redox process,which was the reason for the formation of SO₄^-·and·OH.Graphite Nitrogen had smaller covalent radius and higherelectronegativity than C atom.It will induce the transfer of electrons from adjacent carbon atoms to nitrogen atoms.Therefore,positively charged adjacent carbon atoms（in group C=O）will more easily accept the nucleophilic addition of PMS and promote the formation of ¹O₂.（2）Using cyanobacteria carbon as the loading material,the cyanobacteria carbon loaded zero valent iron material（NZVI@ACC）was prepared by liquid-phase reduction method.The characterization results showed that nano zero valent iron was firmly loaded on cyanobacteria carbon and modified by zero valent iron.The NZVI@ACC surface contains functional groups such as C=C,C=O,-OH.The NZVI@ACC specific surface area was 49.249 m²/g,the pore volume was 0.104 cm³/g,and the average pore diameter was 19.196 nm.The cyanobacteria carbon material can effectively reduce the agglomeration of nano-sized zero valent iron,and the pore structure and active sites were significantly improved.The factors affecting the degradation of OII in NZVI@ACC/PMS system were explored.The optimal conditions were reaction temperature of 25 ^oC,initial p H of OII was 6 and carbon iron ratio of 1:1NZVI@ACC,the dosage was 1 g/L and 0.28 g/L PMS,the reaction could reach 98.32%in 14 min.The reaction mechanism was explored,and the results of inhibition experiment and free radical capture showed that the active groups that played a major role in the degradation of OII by NZVI@ACC/PMS were·OH and SO₄^-·.A large amount of SO₄^-·produced by PMS attacks the 12（N）site of OII.The structure of OII was destroyed and degraded into small molecular organics,such as aniline and naphthalene.Finally,it was completely degraded into small molecules(CO_2,H₂O).Considering the practical application performance of NZVI@ACC/PMS system can degrade different dyes（CR,OII,RB,MB）,and the removal rate of anionic dyes was significantly higher than that of cationic dyes.When there were halogen ions（Cl^-,Br^-,I^-）in the solution N@ACC/PMS and NZVI@ACC/PMS system had inhibitory effect,and the inhibitory effect was I^->Br^->Cl^-.The two doping modified cyanobacteria carbon methods used in study can realize the effective activation of persulfate,which provides a research reference for the treatment and disposal of cyanobacteria,the activation of persulfate and the removal of dye wastewater such as orange II.