Study On The Treatment Of Wastewater Containing Polyvinyl Alcohol By Iron Carbon Microelectrolysis Combined With Fenton Oxidation Method

Polyvinyl alcohol（PVA）is an important polymer material widely used in various fields such as fiber manufacturing,adhesives,coatings,binders,packaging materials,and medicine.Although PVA itself is not toxic,its strong surface activity can produce a large amount of foam and water film in water,which can affect the process of water reoxygenation,leading to the inhibition or even destruction of the respiration activities of aquatic organisms.Therefore,direct discharge of wastewater containing PVA will have serious environmental impacts.Due to the poor biodegradability of PVA,traditional biochemical treatment methods are not effective.This study analyzed the water quality characteristics and indicators of PVA wastewater,and used the iron-carbon micro-electrolysis coupled with Fenton oxidation method to effectively degrade PVA wastewater.The optimal process parameters were studied in detail,and the degradation mechanism of PVA was preliminarily explored.The main research contents of this paper are as follows:（1）Find the optimal process conditions for using iron-carbon micro-electrolysis to treat PVA wastewater.The effects of aeration volume,iron-carbon dosage,reaction time,and p H on the degradation of PVA wastewater were studied through single-factor experiments.The appropriate range of process parameters was initially determined,and the optimal process conditions were obtained through response surface methodology:p H of 1.8,reaction time of2.5 hours,and aeration volume of 4.3 L/min.Under these conditions,the removal rates of COD and PVA in the PVA wastewater with a concentration of about 800 mg/L reached 62.26%and64.88%,respectively.（2）Iron-carbon micro-electrolysis coupled with Fenton oxidation method was used to treat PVA wastewater.The effects of reaction time,p H,ferrous sulfate dosage,and hydrogen peroxide dosage on the degradation of PVA wastewater were explored through single-factor experiments.The optimal process conditions obtained through response surface methodology were as follows:p H of 3.17,ferrous sulfate dosage of 0.15 g/L,and hydrogen peroxide dosage of 0.4 m L/L.Under these conditions,the removal rates of COD and PVA in the simulated PVA wastewater reached 35.91%and 99.99%,respectively.（3）The mechanism of PVA degradation by the iron-carbon-Fenton method was preliminarily studied.Through studying the relationship between the total amount of iron ions in the iron-carbon phase and COD,it was found that there is a significant correlation between the two.By tracking the changes in the concentrations of iron ions and hydrogen peroxide in the solution,it was shown that the reaction rate of the Fenton oxidation process is extremely fast and can complete most of the oxidation work within 10 minutes.The trend of changes in TOC,TC,TIC in the solution and the change in PVA concentration confirmed that the iron-carbon coupled Fenton oxidation method can degrade PVA and generate CO₂ and water.The results of gel permeation chromatography showed that（1）iron-carbon micro-electrolysis can effectively promote the depolymerization of PVA,and some PVA can be converted into small organic molecules;（2）using the Fenton oxidation method can decompose PVA into small organic molecules,causing complete depolymerization.The analysis results of UV-Vis absorption spectroscopy showed that during the degradation of PVA,the functional groups undergo changes.By treating PVA simulated wastewater with micro-electrolysis technology,some structurally complex,long-chain,cyclic intermediate products may be produced,and intermediate products with C=C and C=O double bonds may also be generated under[H]attack.The results of infrared spectroscopy analysis showed that after Fenton oxidation treatment,a new absorption peak appeared at 621cm^-1 in PVA wastewater,which is speculated to be detected due to the generation of ferrous sulfate or iron sulfate or thiol-like substances.After Fenton oxidation treatment,many small peaks appeared at the wavenumber range of 784 cm^-1 to 1172cm^-1,indicating that PVA was decomposed into many small molecules through the iron-carbon micro-electrolysis coupled with Fenton oxidation method.There was an absorption peak at the wavenumber of 1369 cm^-1,indicating the presence of aromatic amine substances in the original PVA water,and the content increased after micro-electrolysis treatment and decreased after Fenton oxidation treatment.This suggests that the combination of iron-carbon micro-electrolysis and Fenton oxidation can effectively decompose and transform aromatic amine substances,which are intermediate products rather than terminal products.After 2 hours of iron-carbon micro-electrolysis treatment,the absorption peak at the wavenumber range of 1600 cm^-1 to 1620 cm^-1 became stronger,which usually corresponds to the stretching and vibration of the carbonyl group（C=O）in aromatic carboxylic acid molecules.After Fenton oxidation treatment,this absorption peak weakened,indicating that the Fenton oxidation method has a significant degradation effect on aromatic carboxylic acid molecules.