Treatment Of Imidacloprid And Organicsilicon Wastewater Based On Electrochemical And Photochemical Oxidation Processes

In recent years,with the rapid development of modern industry as well as the increase of living condition,the water pollution problem is an emerging issue.Thus,the traditional wastewater treatment was difficult to degrade the toxic and biorefractory organic pollutants.Over the past few years,advanced oxidation processes(AOPs)have been receiving great attention for degradation and mineralization of organic pollutants in aqueous medium.The traditional Fenton technology is based on hydroxyl radical degradation of organic pollutants.Based on the similar mechanism,variety Fenton-like processes were developed to make up for the deficiency of traditional Fenton technology,including electro-Fenton process,photo-Fenton process and sulfate radical based the advanced oxidation processes technologies,etc.The Fenton-like processes have attracted more extensive attention of researchers.In this paper,homogeneous Fenton process and heterogeneous Fenton process were used to degrade different kinds of industry wastewater.Based on the experiment,we could get the following results and conclusions:In the first part,we compared several different combination systems to degrade organicsilicon wastewater.Finally,the modified EC/Fe2+/PDS system exhibits a rapid and continuous oxidation of organic contaminants.The system presented the obvious synergistic effect for the degradation of organicsilicon wastewater.Under the optimum conditions peroxide,the COD removal efficiency of wastewater could reach above 70.5%in 360 min.The effects of several operational parameters were discussed.Results showed that the initial pH will not affect the degradation efficiency.Within a certain range,the degradation efficiency of organicsilicon wastewater increased with increasing dosage of ferrous,hydrogen peroxide and current density.There still has iron sludge generated after the reaction,and the organicsilicon wastewater could not be degraded completely.Therefore,it is essential to develop other effective treatment technology.In the second part,the degradation of organicsilicon wastewater by UV-based photolysis processes was explored.We compared three different oxidants.And the effects of initial pH,oxidant concentration were investigated.We also compared the energy consumption of the three processes,respectively.Finally,the characteristics of dissolved organic matter(DOM)were identified by the excitation emission matrix fluorescence spectroscopy and parallel factor analysis(EEMs-PRAAFAC)method in the system.Compared with the degradation efficiency was worse when under alkaline conditions in UV/H2O2 system,the degradation efficiency of UV/PDS and UV/PMS system were increased.COD removal rate increased with higher concentrations of oxidant in a certain range.The results indicated that the UV/H2O2 process is more efficient and economic than the other processes for degrading the organicsilicon wastewater.Through the analysis of the EEMs-PRAAFAC,the three kinds of DOM in organicsilicon industry wastewater(tyrosine,tryptophan and humic acid-like substances)were significantly degraded into the fractions with small molecular weight as the fluorescence peaks disappeared.In the third part,we used an iron oxide(BT)as heterogeneous catalyst,which a by-product resulting from the non-seeded fluidized-bed Fenton reaction for the treatment of the bio-effluent tannery wastewater from a leather plant in Taiwan.Imidacloprid was mineralized in a three-phase fluidized bed reactor by heterogeneous photo-Fenton process was reported.The mineralization efficiency of imidacloprid increased with increasing dosage of catalyst and hydrogen peroxide.The optimum operational conditions were:the pH value was controlled at 3.5±0.2,the dosage of catalyst was 5 g/L and the concentration of hydrogen peroxide was 105 mM,respectively.Under the optimum conditions,the mineralization efficiency of imidacloprid(TOC0 497 mg/L)could reach 97.7%in 6 hours.Even more,the mineralization rate could also reach 94.1%in 4 hours.The stability of catalyst was observed by recycle experiments.The result showed that the catalyst remains a high level of stability.Oxygen participated in the mineralization process of imidacloprid and played an important role,it can be used as oxidant in the reaction and through different ways to improve the mineralization efficiency in this system.We also determined the changes of different kinds of inorganic nitrogen such as NH4+,NO3-,and NO2-.The results showed that the nitrogen initially present in the organic compounds was mainly converted into NH4+ and NO3-.Combined with the TOC results can further prove that this process is a powerful method for mineralization imidacloprid.