Study On Degradation Of Pyridine By UV-Activated Persulfate And Hydrogen Peroxide Technologies

Pyridine,nitrogen-containing heterocyclic compounds,is widely found in various industrial wastewater.Pyridine has"three effects",which is highly toxic and difficult to biodegradation.It is easy to accumulate in environment and seriously affects health of animals,plants and human beings.In multiple pyridine wastewater treatment technologies,the advanced oxidation technologies?AOPs?have gradually coming into view,because of theirs advantages of high efficiency,cleanliness,mild reaction conditions and without secondary pollutions.In a variety of AOPs,ultraviolet light activation can produce radicals stably,high oxidation efficiency,operation easily and less by-products.It has great potential to degradation of refractory organic pollutants.The degradation of pyridine in simulation wastewater is studied using UV/PS and UV/H₂O₂ process,which is based on the photochemistry advanced oxidation technologies.The effects of UV-light intensity,oxidation dose,initial pH value,reaction time and chloride ion concentration on the degradation of pyridine is investigated by single factor experiments.The BBD response model is constructed to determine the interactions between dosage of oxidant,initial pH value and reaction time.The best experimental conditions are obtained by the response surface analysis.Identifying the main types of radicals.The intermediate products and possible degradation pathway of pyridine is deduced from ultraviolet spectrogram and TOC removal rate.The experimental results show that:?1?The best reaction conditions of UV/PS process degradation pyridine are determined by the single factor tests and the response surface analysis.Under the optimum reaction conditions,when the initial pyridine concentration is 20mg/L,UV-light intensity is 9.94 mW/cm²,the concentration of PS is 1.04mmol/L,initial pH value is 3 and reaction time is 34.62 min,the pyridine degradation rate using UV/PS process is 98.07%,and the effluent concentration of pyridine is 0.386 mg/L.?2?The best reaction conditions of UV/H₂O₂ process degradation pyridine are determined by the single factor tests and the response surface analysis.Under the optimum reaction conditions,when the initial pyridine concentration is 20 mg/L,UV-light intensity is 9.94 mW/cm²,the concentration of H₂O₂ is1.56 mmol/L,initial p H value is 7.5 and reaction time is 37.39 min,the pyridine degradation rate using UV/H₂O₂ process is 94.69%,and the effluent concentration of pyridine is 1.062 mg/L.?3?Using Two kinds of radical scavengers identify the main types of radicals.The results show that the main radical in UV/PS system is sulfate radical?SO₄^-·?,while the main radical in the UV/H₂O₂ system is hydroxyl radical?·OH?.?4?Through ultraviolet spectrogram and TOC removal rate,the degradation products and possible reaction pathway of pyridine is speculated in two kinds of advanced oxidation technologies.In UV/PS and UV/H₂O₂ system,pyridine is oxidized by SO₄^-·and·OH radical respectively.It firstly generates inorganic acids of small molecules,and eventually mineralizes into carbon dioxide,water,ammonia nitrogen and other inorganic substances.?5?The comparison of UV/PS and UV/H₂O₂ process to degrade pyridine finds that the pyridine degradation rate of UV/PS is higher than UV/H₂O₂under the same amount of oxidants or the best experimental conditions.However,UV/H₂O₂ technology is better to remove TOC.In addition,under the weak alkaline condition,UV/H₂O₂ process has great degradation effect.It doesn't need to adjust pH value,and has the simple operation.