Efficient Degradation Of M-phenylenediamine By NaBiO₃

As dye industry is developing, a lot of Aniline wastewatercontainingm-Phenylenediamine is pouring into the water,leaving negative effects onhuman health and the environment. Nowadays, more attention are focused to removeit from environment.Among low-degradation chemical methods, NaBiO3can play animportant role in removing harmful organic compounds in an efficientlyway. In thisstudy, NaBiO3was chosen as thematerial to investigate its degradation behavior. Themethod having these advantages as low cost and simple operation.In this study, m-Phenylenediamine was chosen as the target organic pollutant toinvestigate its degradation behavior over NaBiO3. It was studied by individualexperiment and orthogonal test to explore the influence of the initial concentration,pH, NaBiO3dosage and temperature. Basing on the above, The best workingcondition was calculated.Dynamic model, dynamic rate equation, and TOC were alsoanalyzed. The goal was aimed at the investigation of aniline degradation and thepresentation of mechanistic details of the photochemical process.The mainconclusions are as below:(1) It was found that the NaBiO3effect was better in the acidity condition. Theremainder m-Phenylenediamine in the acidity was less than that in the neutral andalkaline condition. When pH was3, the removal rate can reach to75%in the5minutes, whereas the removal rate in the neutral and alkaline condition werebelow60%, respectively.The result showed that the oxidation efficiency wasincreasing with time temperature and NaBiO3dosage increasing correspondingly. CI-had a good effect on the degradation.(2) The best working condition was when pH was3, NaBiO3dosage was0.75g/L,time was120min initial concentration of aniline was20mg/L.(3) The degradation was in the coincidence with first-order kinetic model anddynamic rate equation of Langmuir-Hinshelwood. When the initial pH value was3,its pseudo-first-order rate was up to0.0711min-1, which was far more than others’,When initial m-Phenylenediamine concentration was30mg/L, the pseudo first orderrate constant was0.0774min-1.The degradation efficiency decreased with increasinginitial aniline concentration. The degradation by different NaBiO3dosage all conformed to the first-order kinetic model. As the dosage was increasing, the pseudofirst order rate constants was more larger.(4) As there is a amidogen in the m-Phenylenediamine structure, there aretransformation of nitrogenin the process.The removal rose in the first30min of thedegradation, the concentration of ammonia nitrogen and nitrate were increasing.Nitrites were produced as the intermediates of nitrate, and the concentration was lowon the whole.(5) In the Bi(III)—Cl-—H2O, Bi(III) could combine with Cl-into BiOCl, which issediment having little influence on environment. Analysis on the TOC can help toclarify the details of the reaction. In the given condition, m-Phenylenediamine couldbe degraded completely in the30min while TOC still left60%. As the reaction goeson, m-Phenylenediamine could react with·OH. Its products would go into two parts.One part would be mineralized directly, while the other part opened ring then beingmineralized, meanwhile N-ionogen turned into mineral nitrogen.The results showed that the degradation of m-Phenylenediamine over NaBiO3had better efficiency and simpler operation comparing with traditional chemicaltechnology.