以顆粒活性碳為擔體之流體化床-Fenton中吸附、催化及化學氧化再生作用之探討

Abstract

高級氧化程序是利用氫氧自由基的強氧化力來分解水及廢水中的有機物。許多研究證明Fenton試劑（H2O2/Fe2+）是一種有效而簡單的氧化劑，但其缺點是在反應過程中會產生大量的氫氧化鐵污泥，而需進一步作固液分離及污泥處置。為解決此問題，以H2O2為氧化劑，氧化鐵作為異相觸媒之氧化程序值得進一步研究。 本研究結合Fenton反應及流體化床結晶的技術，不僅可解決傳統Fenton法的固液分離及污泥處置問題，且具有高質傳效率及較易處理難分解有機物的優點，為一新開發的高級氧化程序。在本論文中將探討以活性碳為擔體之氧化鐵覆膜活性碳的製備、使用氧化鐵覆膜活性碳進行批次吸附及氧化苯甲酸的研究、以及此以活性碳為擔體之Fenton流體化床結晶槽中吸附/催化/化學氧化再生程序之研究。 在流體化床操作條件方面，探討不同觸媒量及反應停留時間對COD及總Fe去除率的影響。結果顯示流體化床中填充的氧化鐵覆膜活性碳愈多，對總Fe的去除率也較高，表示在活性碳表面的結晶愈多；而反應停留時間愈長，COD及總Fe去除率愈高。 在批次吸附及氧化苯甲酸的研究部分，先對活性碳及兩種氧化鐵覆膜活性碳進行24小時恆溫吸附實驗，結果顯示活性碳及兩種氧化鐵覆膜活性碳之最終pH低時吸附效果較pH高時好，另外原始活性碳吸附效果較氧化鐵覆膜活性碳A、B都好；至於氧化鐵覆膜活性碳B之吸附效果又比氧化鐵覆膜活性碳A好。然後進行批次氧化實驗，研究以此二種觸媒催化氧化苯甲酸之可行性，發現加入Fe2+能提升催化氧化的能力，而氧化鐵覆膜活性碳A對苯甲酸的催化氧化效果較好。另外也證實H2O2的存在會加速氧化活性碳，而使溶液中的TOC濃度增加。 最後進行約六週的實驗探討以活性碳為擔體之Fenton流體化床結晶中吸附/脫附/催化氧化的再生程序，先經過約二週的長晶（進流有機物、NaHCO3及Fenton試劑）→一週的正常操作→一週之提高二至三倍進流有機物負荷→一週之提高進流十倍有機物負荷→接著停止有機物進流但仍持續Fenton試劑進流一週（再生）→最後再恢復正常進流，觀察此連續過程中COD去除率之變化，並在再生時期前後取具代表性時點的觸媒做苯甲酸吸附容量的測定，由COD去除率及苯甲酸吸附容量變化得知，此程序確實能使活性碳再生。

Hydroxyl radical（·OH）is very oxidative, which is the base of advanced oxidation process（AOPs）for degrading organic compounds in water and wastewater. Fenton’s reagent（H2O2/Fe2+）has been proved in a lot of studies to be an effective and simple oxidant, but the drawback is the production of substantial amount of Fe（OH）3 sludge that requires further seperation and disposal. To solve this problem, the application of H2O2 as oxidant and iron oxide as the heterogeneous catalyst in oxidizing organic contaminants deserves further investigation. In This study, a novel technology which combines Fenton reaction with fluidized bed reactor was developed. It not only desolves the seperation and disposal problem of traditional Fenton’s method but is highly efficient in mass transfer and degrading organic compounds. The preparation of GAC-supported FeOOH, batch adsorption and oxidation using FeOOH-GAC and GAC, GAC as supporter in Fenton-fluidiaed-bed reactor：adsorption, catalysis and chemical oxidation regeneration was investigated. In the part of operating condition of fluidized bed, the influence of different catalyst vloume and hydrous reaction time to COD and total Fe removal was investigated. The result indicated that the more the FeOOH-GAC was filled, the higher the Fe removal, meaning the more crystal on the GAC surface；besides, the longer is the HRT, the higher is the COD and total Fe removal. In the part of study of batch adsorption and oxidation, the 24 hours isothermal adsorption experiment of GAC and the two FeOOH-GAC were performed first, the result indicated that their adsorption efficiency was better at low pH than at high pH, and that the adsorption efficiency of GAC was higher than that of the two FeOOH-GAC；the adsorption efficiency of FeOOH-GAC(B) is higher than that of FeOOH-GAC(A).Subsequently the batch oxidation experiment was performed to investigate the feasibility of the catalysis oxidation of BA of the two catalyst, the addition of Fe2+ was found able to increase the catalysis oxidation. Besides, the existance of H2O2 was proved to increasingly oxidate GAC, and increased the TOC concentration of solution. Eventually an experiment for six weeks was performd to investigate the adsorption/catalysis/chemical oxidation regeneration process of the Fenton fluidized bed using GAC as supporter, which was crystallized for 2 weeks（inflowed organic compounds, NaHCO3 and Fenton reagent）→normally performed for 1 week→2~3 times the inflow organic compounds for 1 week→10 times the inflow organic compounds for 1 week→stopped the organic compounds inflow but continued the Fenton reagent inflow for 1 week→normal inflow, the change of the COD removal was observed during the process, then select and take out catalyst at typical time point to measure the quantity of BA adsorbed, from the change of COD removal and BA adsorption capacity, GAC was regenerated during the process.