Study On Degradation Of Nitrobenzene And Aniline In Wastewater By Dielectric Barrier Discharge

Water is an essential part of life.As a result of natural and human activities toxic and hazardous chemicals enter the waterbodies resulting in deterioration of its quality thus pushing the life of all living beings in danger.Because industrial wastewater usually contains a large number of harmful and toxic chemicals,untreated or improperly treated wastewater is discharged into the water body,resulting in water pollution.Nitrobenzene and aniline are highly toxic and extensively used chemicals in various industries for a range of applications therefore these chemicals are widely present in their effluents.Water scarcity and water contamination due to extensive use of organic compounds in industries initiate us to adopt modern techniques for wastewater treatment.The basic purpose of this research was to degrade and mineralize nitrobenzene and aniline in water using an efficient dielectric barrier discharge(DBD)reactor under different physical and chemical parameters such as initial pollutant concentration,voltage,solution p H,air flow rate,addition of promoters and inhibitors etc.Additionally to evaluate this DBD reactor’s performance for its energy yield,degradation efficiency,treatment volume and treatment time by comparing it with other advanced oxidation processes(AOPs).A series of separate experiments were performed to achieve these goals which are abstracted as following;(1).Dielectric barrier discharge(DBD)reactor was employed for the degradation of nitrobenzene in aqueous solution.Active species like ozone(O3)and hydroxyl radical(·OH)produced by DBD reactor were mixed with water which degraded the NB.The results indicated that the lower NB concentrations slightly acidic conditions and high voltage ranges showed the optimum efficiencies.Moreover,the impacts of active species inhibitors isopropyl alcohol(IPA),tert-butanol(TBA),sulfates(SO42-),bicarbonates(HCO3-),nitrates(NO3-),carbonates(CO32-)and chlorides(Cl-)on the degradation of NB were examined.This analysis showed that the hydroxyl radical was captured by the addition of these inhibitors and resulted the decrease in efficiencies and proved that hydroxyl radicals are main active species for DBD treatment.Byproducts produced during the degradation of nitrobenzene were assessed by analytical techniques of highperformance liquid chromatography(HPLC),liquid chromatography-mass spectrometry(LC-MS),UV-visible spectroscopy and total organic carbon(TOC)analysis.Fourier transform infrared spectroscopy(FTIR)analysis confirmed the formation of oxalic acid and the presence of OH radicals as a vigorous active specie in DBD treatment.Main intermediate products were nitrophenols and low molecular weight organic acids including oxalic acid and acetic acid that were eventually mineralized to carbon dioxide and water.The dielectric barrier discharge technology was found productive for the degradation of nitroaromatic compounds.(2).Herein performance evaluation of dielectric barrier discharge under different conditions for nitrobenzene degradation was done.A new dielectric barrier discharge(DBD)system was developed which was evaluated for the degradation of nitrobenzene in water under different experimental arrangements.DBD produces an enormous amount of active species like O3,·O,O2+ and O2-and ·OH to degrade the pollutants.In this study,DBD system was evaluated on the basis of changing the gas flow rate,adopting different carrier gas,by adding promoters and the effect of applied voltage on the production of active species to check the effectiveness of the DBD system.The DBD system was assessed based on input power,degradation efficiency and energy yield comparing with other advanced oxidation processes.The energy yield of the DBD system was 1.253 g/k Wh for the degradation of 20 mg/L of NB to 75 % in 60 minutes.These findings display superior results in comparison with the other AOPs regarding energy yield and the degradation efficiency of the pollutant.The results illustrate the significance of the system and further suggest its application to the industrial-scale treatment.(3).Herein degradation of aniline by dielectric barrier discharge in aqueous solution was carried out.Aniline is a priority pollutant that is detrimental to humans and the environment due to its carcinogenic and mutagenic nature.Degradation of aniline in aqueous solution was conducted using a dielectric barrier discharge system to get the optimum results for its degradation and to access the system’s performance.Different parameters were kept under consideration to be able to treat diverse wastewater scenarios.Role of active species like O3 and OH radical for aniline degradation was investigated by the addition of inhibitors and promoters and varying the p H and voltage.The results showed that 87 % of aniline was degraded in 60 minutes of dialectic barrier discharge treatment at 1.8 k V and 4 L/min of oxygen flow.UV-Vis spectra showed the gradual increase in the treatment efficiency of aniline with time.TOC analysis and the decrease in p H during the process determined the mineralization if aniline.HPLC and LC-MS were used to detect the intermediate and byproducts and to propose a degradation pathway of aniline.It was concluded that aniline was degraded to different byproducts and eventually mineralized to CO2 and H2 O.Comparison with other advanced oxidation processes showed that dielectric barrier discharge system has a remarkable potential for the removal of organic pollutants and further research need to be done to launch it for industrial scale.