The Research On Upgrading Fenton Process Advanced Treatment Of Straw Pulp And Papermaking Wastewater

The traditional Fenton process was proven to be effective for straw pulp and papermaking wastewater treatment, but demonstrated a problem with high operating cost. In this study, the effluent from aeration tank was treated using various modified Fenton process. A feasible retrofit scheme, with the aiming of reducing operating cost, was selected and optimized. Furthermore, a new heterogeneous Fenton catalyst was also developed.The polarity, molecular weight distribution and organic matter types of the pulp and papermaking wastewater were analyzed. It was found that the main organic matter in wastewater was macromolecular organic matter whose molecular weight was greater than 3 k Da, accounting for about 93.7% of TOC in the wastewater. Most organic matter was proven to be hydrophobic. Since the strong hydrophobic organic compounds accounted for 59.2% of TOC in the wastewater.The process parameters of traditional Fenton process treating papermaking wastewater were evaluated through orthogonal tests and single factor tests. The experimental results showed that the process parameters affecting the CODCr removal performance in following order: H2O2 dose > pH > Fe2+ dose > reaction time. The best operating conditions of this process was reaction pH value of 3, H2O2 dosing of 8 mmol/L, n(H2O2: Fe2+) = 2:1, the reaction time of 30 min. The cost of reagent was calculated to ?1.0-1.7 yuan/m3 approximately.According to this wastewater characteristics, three kinds of proposed schemes:Coagulation-Fenton, alkali out-Fenton and step-feed-Fenton were brought forward and investigated. The final results showed that the coagulation-Fenton process presented better performance than the other two modified Fenton processes. The optimal operating conditions of the combined coagulation-Fenton process were determined. The suggested operating conditions of coagulation sedimentation pretreatment were: initial pH in the reaction of 5, PAC dosing quantity of 72 mg/L, PAM dosing quantity of 1 mg/L, quick stir time of 2 min, slow stir time of 5 min, static sink 30 min. The suggested operating conditions of Fenton oxidation were: the initial pH value of 3, n(H2O2: Fe2+) = 1:1, H2O2 dosing quantity of 2 mmol/L, reaction time of 30 min. Finally, the reagent cost of the combined coagulation- Fenton process was ?0.83 yuan/m3, which was much lower than ?1.3 yuan/m3 of the traditional Fenton process.A new heterogeneous Fenton catalyst compsed of both Mn and Fe element was developed. Two preparation methods of by immersion or citric acid sol-gel were both utilized to produce the catalysts. The CODCr removal efficiencies using immersion preparation methods achieved as high as 70%, the other is 65%. The catalysts could be reused with low decrease of CODCr removal efficiencies(50% after three times reuse), which was due to the erosion of metal ion loaded on the molecular sieve.