Study On Photoelectrocatalytic Treatment Of Wastewater Containing HAPM By Cobalt Tetrapyrazinoporphyrazine Derivatives

Tetrapyrazinoporphyrazines and their metal derivatives(MTPyzPzs)are the most widely studied class of azaanalogues of phthalocyanines(Pcs).Peripheral substituents endow MTPyzPzs with not only solubility in organic or aqueous solvents,but also fine-tune spectral and other physicochemical properties and biological activity,which can play better catalytic performance.In this study,cobalt(?)1,4,8,11,15,18,22,25-octaaza-phthalocyanine(CoTPyzPz)and cobalt(?)2,3,9,10,16,17,23,24-octa-methyl-1,4,8,11,15,18,22,25-octaaza-phthalocyanine(MeCoTPyzPz)were synthesized according to the literatures.Also,I improved a new synthetic method of cobalt(?)2,3,9,10,16,17,23,24-octa-t-butyl-1,4,8,11,15,18,22,25-octaazaphthalocyanine(t BuCoTPyzPz),and the optimum molar ratio of 2,2,5,5-tetramethylhexane-3,4-dione: 2,3-diamino-2-butenediuronitrile: urea: hydrated cobalt chloride was screened out 2: 2: 6: 0.75,when the yield was increased to 81.6%.The catalysts were loaded onto conductive carbon black(CB)and conductive polyaniline(PANI),respectively,using an ultrasonic impregnation method.The photocatalytic and electrocatalytic units were used to form the photoelectrocatalytic system,which was prepared by using the 300 W xenon lamp as the light source,the supported catalysts as the particle electrode and the titanium plate / stainless steel plate as the main electrodes.The photoelectrocatalytic degradation performance of catalysts was investigated by treating the anionic polyacrylamide(HPAM)solution,which the initial concentration was 50 mg/L.The results showed that a synergistic effect was produced besides the photocatalytic and the electrocatalytic effects in the photoelectrocatalytic system.The phthalocyanine catalysts had no catalytic performance in the electrocatalytic system without any carriers,so the removal rate and viscosity reducing of HPAM was significantly lower than that of the photocatalytic process.After loading on the conductive carrier,it constituted a complete three-dimensional electrocatalytic system,and produced effective reaction current,which resulted in electrolysis reaction to produce hydroxyl radicals and superoxide radicals to degrade HPAM.Among the catalysts,t BuCoTPyzPz/CB was the best,which the removal rate reached 94.55 % and the viscosity dropped to 0.32 mPa·s.With the analysis of single factor influence on the photoelectrocatalytic system,it was found that the best experimental factors could not only maximize the synergistic effect,but also saved raw material and energy consumption.In the combination system,the power consumption of photocatalytic process increased.Nevertheless,the combined process shortened the degradation time and enhanced the usage efficiency of unit power.Among all the catalysts,tBuCoTPyzPz/CB achieved the highest pollutant removal efficiency and energy efficiency under the same conditions.Dynamics research was carried out with the process,it was confirmed that the degradation of HPAM of the single catalytic process was in accordance with the quasi-first order reaction kinetics formula,which is the same as the synergistic degradation of HPAM.The response surface analysis of photoelectric synergistic catalytic process was carried out by Box-Behnken method.The prediction model was established by using the amount of catalyst,the voltage and the electrolyte concentration as the independent variables,the HPAM removal rate as the dependent variable.I had verified the prediction model,and the prediction results were consistent with the measured results.In particular,increasing the catalyst dosage,cell voltage and electrolyte concentration could increase the HPAM removal rate.In contrast,the effect of the cell voltage played a more important part than other two factors,at which time the electrocatalytic oxidation performance was fully released.The optimized parameters of the photoelectrocatalytic process were follows: the catalyst dosage was 0.36 g/L,the cell voltage was 40.51 v and the electrolyte concentration was 0.1492 mol/L.The cyclic voltammetry curve of tBuCoPPz/CB particle electrode was determined by electrochemical workstation.Electron spin resonance(ESR)technology was used to determine the active species in the photoelectrocatalytic system.The results showed that the degradation of HPAM was quasi-reversible redox reaction,and the major active species were hydroxyl radicals and superoxide radicals in the process.Through the analysis of the reaction intermediates,the degradation path of HPAM under the condition of this study was as follows: the long chain of HPAM molecular was broken to form short chain HPAM molecular,which continued to be oxidized by radicals to produce small molecules such as acrylamide monomer and acrylic acid,and the last oxidation products were nitrate,carbon dioxide and water.The HPAM degradation relied on the oxidation of the photoelectric synergistic system,and the two separate processes played their respective catalytic degradation,meanwhile the other process also produced an additional enhancement effect.The increase in the yield of active species under this complex interaction was the main reason for the synergistic enhancement.Based on the research results of photoelectrocatalytic process,the two signal catalytic processes were combined simply,however,we could also get significantly synergistic enhancement effect besides to the two processes respective degradation effects.This photoelectric combined process has many advantages,such as the simple combination and the rapid treatment for refractory wastewater,which exhibits a certain practical value for the improvement of existing facilities.Meanwhile,the low energy consumption,relatively mild reaction conditions and the good stability,low cost,non-toxic catalysts are required to make the photoelectrocatalytic synergistic process become a highly promising water treatment technology.