Synthesis Of Biomimetic Magnetic Modified Water Treatment Agent And Their Catalytic Mechanism

In this paper, a novel biomimetic nano magnetic bentonite composite materials forthe advanced treatment of persistence organic wastewater were successfully synthesizedby loading the nano-sized particles of Fe3O4on organic modified bentonite. Thepreparation of biomimetic catalysts and the mechanism of catalytic degradation onorganic pollutants were investigated. The main research conclusions are as follows:（1） Different morphology of Fe3O4nanoparticles were prepared bycoprecipitation method and oxidation precipitation method. Orthogonal experimentanalysis and single factor experiment were used to determine the best syntheticconditions of the two synthetic methods, respectively. The best preparation conditions ofcoprecipitation method were m[Fe2+]/m[Fe3+]=3:4, T=80°C, pH=10,[Fe]=0.10mol L-1.The best preparation conditions of oxidation precipitation method were T=90°C,[OH-]=0.20mol L-1,[NO3-]=0.15mol L-1,[Fe2+]=0.50mol L-1. Using Orange Ⅱ assimulated wastewater to synthetically compare the catalytic effect of nano Fe3O4onorange II and the complexity of the preparation through the two methods, then selectingoxidation precipitation as synthetic methods of imitation of enzyme of nano magneticwater treatment agent.（2）Organic modified bentonite were synthesized by cationic surfactants andbentonite with cationic exchanging. The best modification conditions were obtainedthrough the orthogonal experiment: m[surfactant]/m[bentonite]=0.3, T=40°C, t=60min,pH=9. The synthesized materials were characterized by X-ray diffraction (XRD), Fourierinfrared ray (FT-IR) and scanning electron microscopy (SEM), characterization resultsindicate that the d001basal spacing increased from1.5134nm to1.9555nm. And thecation exchange capacity, specific surface area, the orange II decolorizing rate of themodified bentonite were also improved, it was proved that organic modified bentonitehad been synthesized successfully, and the adsorption of organics by organic modifiedbentonite was according with the Langmuir adsorption model. Using the organicmodified bentonite, with the best modification condition, as carrier of nano magneticwater treatment agent.（3）Biomimetic nano magnetic bentonite composite materials were obtained by loading nano Fe3O4on organic modified bentonite with in-situ oxidation-coprecipitation.The Fe3O4nano-particles in spherical form was loaded on the surface of bentonite andthe load was firm, in addition, bentonite was still maintained its layer structure, theaverage particle size of Fe3O4were around100nm, and the optimal loading level ofFe3O4nanoparticles was50%. The degradation of orange II by magnetic bentonitecatalytic was optimized by the response surface methodology (RSM) based onBox-Behnken design (BBD), optimum conditions were [catalyst]=1.5g L-1, pH=2.7,T=42°C and [H2O2]=22mmol L-1, respectively. The predicted decolorization rate underthe optimum conditions was99.55%. Confirmatory tests were carried out and thedecolorization rate of99.49%was observed under the optimum conditions, which agreedwell with the model predictions. The data indicate the strategy to optimize thedecolorization conditions, and to obtain the maximal decolorization efficiency by RSMfor the decolorization of the dye Orange II in this study was successful. In thedegradation of orange II by biomimetic magnetic bentonite/H2O2, biomimetic magneticbentonite displayed good chemically stability. The heterogeneous biomimetic catalyticreaction occurred on the catalyst surface was the main way of the orange II degradation.（4）To verify the degradation effect of biomimetic magnetic bentonite on realindustrial organic wastewater, the coking wastewater after secondary treatment wasselected as research object. The results show that the CODCrand chroma removal ratecan reach79.3%and93.4%respectively in the following initial conditions:[H2O2]=70mmol L-1,[catalyst]=0.8g L-1, T=30°C and pH=5.0. The final effluent can reachreclaimed water quality standard and catalyst can be recycled. The mechanism ofdegrade organic wastewater by biomimetic magnetic bentonite catalysts was the resultsof the synergies between nano Fe3O4and organic modified bentonite.