Study On Degrdation Of Organic Pollutants By GLDA Enhanced Fe³⁺-（photo） Fenton System At Neutral PH

With rapid industrialization and urbanization,different classes of organic pollutants had beenfrequently found in municipal effluents and surface water which caused serious threat to human health.The common treatment technology always had the low efficiency for degrading refractory organic pollutants.Therefore,it was necessary to develop efficient techniques to treat these refractory organic pollutants.Fenton system was popular for removing recalcitrant organic pollutants in water because it could generate oxidizing free radicals.Moreover,Fenton technology was easy to operate.However,Fenton system usually worked in a narrow p H range（2.5–4.0）.At neutral p H,Fe（III）would convert to iron precipitation,resulting in the decline of valid Fe concentration and the degradation performance of Fenton system.However,wastewater was usually in neutral or alkaline condition.Thus,acidification pretreatment of wastewater was required when Fenton technology used in project.In addition,the reaction rate between Fe³⁺and H₂O₂was low,leading to a bad cycle of Fe³⁺/Fe²⁺.As a result,Fenton system often needed a large amount of catalyst,which greatly increased the processing cost.To apply Fenton technology in neutral condition,and enhance the iron cycle,we introduced GLDA and visible light to Fe³⁺/H₂O₂ system and established two new systems:Fe³⁺/GLDA/H₂O₂ system and Fe³⁺/GLDA/H₂O₂/vis system.The research contents were as follows:（1）Ciprofloxacin（CIP）was chose as the model pollutant.The paper verified both the Fe³⁺/GLDA/H₂O₂ system and the Fe³⁺/GLDA/H₂O₂/vis system had significant advantages in the degradation of CIP at p H 7.（2）The paper explored the effect of experimental factors on the degradation efficiency for CIP in the Fe³⁺/GLDA/H₂O₂ system and Fe³⁺/GLDA/H₂O₂/vis system.For Fe³⁺/GLDA/H₂O₂ system,95.6%of CIP removal was obtained with 100μmol/L Fe³⁺,100μmol/L GLDA,15 mmol/L H₂O₂;For Fe³⁺/GLDA/H₂O₂/vis system,97.85%CIP removal was obtained with 100μmol/L Fe³⁺,150μmol/L GLDA,0.6 mmol/L H₂O₂.It could be seen that the doasge of of H₂O₂ in the Fe³⁺/GLDA/H₂O₂/vis system was much lower than that in the Fe³⁺/GLDA/H₂O₂ system.（3）The study used UV-spectrum experiments,cyclic voltammetry experiments,and iron ion concentration detection experiments to explore the effect of GLDA on the cycle of Fe³⁺/Fe²⁺in the Fe³⁺/GLDA/H₂O₂ system and the Fe³⁺/GLDA/H₂O₂/vis system.The results indicated that GLDA could significantly enhance Fe³⁺/Fe²⁺cycle under neutral condition.（4）The study used EPR experiments and radical quenching experiments to explore the contribution of the radicals in the Fe³⁺/GLDA/H₂O₂ system and the Fe³⁺/GLDA/H₂O₂/vis system.The results indicated that·OH was the only free radical for attacking CIP in both two systems.O₂^·-was responsible for reducing Fe³⁺in two systems.（5）The study used HPLC-MS technology to detect the intermediate products for CIP degradation in the Fe³⁺/GLDA/H₂O₂ system and the Fe³⁺/GLDA/H₂O₂/vis system.