Research On Typical Organics Treatment By Fenton-like Reaction With Iron Complexation In Water

As a kind of advanced oxidation technology?AOPs?,Fenton method has been widely used in the treatment of organic wastewater.The traditional Fenton reaction has the following problems:easy to form iron precipitation,narrow application range of pH?pH2.5-3.5?,easy disproportionation decomposition and low utilization rate of hydrogen peroxide?H₂O₂?.In order to solve the above problems,a Fenton-like method of iron complexation was proposed in this paper to promote the solubility and redox cycle of iron(Fe²⁺/Fe³⁺),broaden the range of pH application,improve the utilization rate of H₂O₂,and further enhance the oxidation capacity of the system.In this study,organic acids and inorganic salts with complexing and reducing abilities were selected as complexing agents,calcium peroxides?CaO₂?and perdisulfates?PS?were selected as oxidants,and three Fenton-like systems were constructed to degrade methyl orange?MO?,a typical organic dye in water,and antibiotics such as sulfamethoxazole?SMX?.Specific research contents were as follows:?1?With CaO₂ as the oxidant and oxalic acid?OA?as the complexing agent,the degradation performance of Fe²⁺/OA/CaO₂ system was established to investigate the decolorization ability of MO under different reaction conditions,and the optimal reaction conditions were determined.When the addition of Fe²⁺/OA/CaO₂ was 1.5 mM:3 mM:3Mm,and the initial pH was 6.55,the decolorization rate of MO reached 97.00%after 15min.The Fe²⁺/OA/CaO₂ system was more effective than the traditional Fenton system,because the CaO₂ could significantly improve the utilization rate of H₂O₂,and the complexation of OA and iron could improve the solubility of iron.Free radicals masking experiments determined that the main active substances in the system were HO^·,O₂^·-and¹O₂.Density functional theory?DFT?calculation analyzed the mechanism of oxidation and complexation.The degradation byproducts of MO in this system were detected by high performance liquid chromatography-mass spectrometry?HPLC-MS?,and the degradation path was also proposed.?2?With CaO₂ as the oxidant and ascorbic acid?AA?as the complexing agent,the degradation performance of Fe³⁺/AA/CaO₂ system was established to investigate the decolorization ability of MO.The response surface method?RSM?was used to determine the optimal condition as Fe³⁺/AA/CaO₂?2.76 mM:0.68 mM:4 mM?,and the maximum decolorization rate of MO was predicted to be 99.30%.The experimental value was98.90%,which was consistent with the predicted value.In comparison experiments of different systems,when the addition of Fe³⁺/AA/CaO₂=2 mM:1 m M:3 Mm,the decolorization rate of MO after 15 min could reach 93.40%.Compared with Fe³⁺/H₂O₂,Fe³⁺/AA/H₂O₂ and Fe³⁺/CaO₂ systems,the removal rates were increased by 64.50%,68.00%and 78.10%,respectively.Comparative experiments showed that AA played an important role in the reduction of Fe³⁺to Fe²⁺.Free radicals scavenging experiments proved that the main active materials were HO^·,O₂^·-and ¹O₂ in the system.?3?With PS as the oxidant and sodium sulfite?Na₂SO₃?as the complexing agent,the degradation performance of Fe³⁺/Na₂SO₃/PS system was established to investigate the degradation efficiency of SMX.RSM was used to determine the optimal condition as Fe³⁺/Na₂SO₃/PS?0.4 mM:0.5 mM:2.5 mM?,and the maximum degradation rate of SMX was predicted to be 100.50%.The experimental value was 100%,which was consistent with the predicted value.In comparison experiments of different systems,when the amount of Fe³⁺/Na₂SO₃/PS=0.5 mM:1 mM:2 mM,the initial pH was 5.96,the SMX degradation rate of SMX was up to 85.00%after 15 min.Free radicals inhibiting experiments and ESR spectrum concluded that the main active radicals were SO₄^·-,HO^·and oxysulfur radicals(SO_x^·-,x=3,5)in the system.The results of biotoxicity simulation showed that the biotoxicity of some SMX degradation byproducts treated by the system were reduced.