Synthesis And Performance Of Biomimetic Magnetic Iron-carbon Composite Catalysts

Phenol-containing wastewater is considered as typical toxic bio-refractory organic wastewater which can cause considerable damage to the water environment.The Fenton-like reagent appeals to researchers.Biomimetic catalytic degradation is more environmentally friendly,however the synthesis of biomimetic catalysts is a hot and difficult point.Biomimetic magnetic iron-carbon composite catalysts were successfully synthesized via oxidation precipitation method,which could be employed to catalyze hydrogen peroxide to oxidize 4-nitrophenol?P-NP?.The catalytic property and reaction mechanism towards P-NP of the catalyst was investigated.The purpose is to develop a novel catalyst of green,efficient and no secondary pollution.The study is summarized as follow:?1?Biomimetic Coke/Fe₃O₄ catalyst was synthesized via an in-situ oxidation-coprecipitation and used as a heterogeneous Fenton-like catalyst to degrade P-NP.Fe₃O₄ NPs were evenly and firmly dispersed on the coke,and its average particle size was about 90 nm.Experimental results showed that the P-NP degradation with Coke/Fe₃O₄ follows pseudo-first-order kinetic rate law;the apparent rate constant for the P-NP was evaluated to be 0.027 min^-1,removal rate of CODCr was 75.47%,and the dissolubility of Fe was 2.42 mg?L^-1 when at the following initial conditions: [catalyst]=1.2 g?L^-1,[H₂O₂]=30 mmol?L^-1,pH=3.0,T=30 ? and the best mass ratio of Coke/Fe₃O₄ was 0.6.Biomimetic Fe₃O₄/Coke catalyst had a good chemical stability and reusability.?2?A composite material?Fe⁰/Fe₃O₄?using Fe⁰ supported Fe₃O₄ magnetic nanoparticles was successfully prepared.The characterization showed that the Fe⁰ and Fe₃O₄ combined steadily,with particle size 60¹80 nm.Experimental results showed that the P-NP degradation with Fe⁰/Fe₃O₄ follows pseudo-first-order kinetic rate law;the apparent rate constant for the P-NP was evaluated to be 0.067 min–1.The best mass ratio of Fe⁰/Fe₃O₄ was 0.75.?3?Biomimetic Coke/Fe⁰/Fe₃O₄ composite materials with good magnetic property were obtained by loading nano Fe₃O₄ on Coke/Fe⁰ with in-situ oxidation-coprecipitation.The degradation of P-NP by biomimetic Coke/Fe⁰/Fe₃O₄ was optimized by the response surface methodology?RSM?based on Box-Behnken design?BBD?.The predicted removal efficiencies 99.21% of P-NP agree well with the experimental values under the best initial conditions: [catalyst]=1.2 g?L^-1,[H₂O₂]=30 mmol?L^-1,pH=3.0,T=30 ?.?4?The organic intermediates were qualitatively analyzed by GC-MS.p-benzoquinone,hydroquinone and 2,4-dinitrophenol were detected during the degradation of P-NP.There were two possible degradation paths of P-NP: one path was that ?OH reacted with NO₂ group to obtain hydroquinone and p-benzoquinone;another path was that ?OH attacked the aromatic ring forming dihydroxycyclohexadienyl radical?DHCHD??,?DHCHD??was then rapidly oxidized to form 1,2,4-benzentriol.?5?The mechanism of degrading organic wastewater by biomimetic magnetic catalysts was the results of the synergies between nano Fe₃O₄,Fe⁰ and coke.Biomimetic Coke/Fe⁰/Fe₃O₄ was a novel green catalyst with high efficiency,non-secondary-pollution and reusability,which provide a theoretical basis for organic wastewater treatment technology with new type,high efficiency,low cost,green and no secondary pollution.