Preparation And Performance Of Magnetic Composites Based On Controllable Fe₃O₄Nanoparticles

In recent years, the advanced treatment technologies for the refractory andcomplex coking wastewater are attracted widespread attention. Among thesetechnologies, advanced oxidation process has gained great attention. Fenton-liketechnology, as a kind of advanced oxidation process, became a hot topic. How todevelop a high efficient and green heterogeneous catalyst became a key factor for theapplication of Fenton-like technology. Based on this, in the present research,thecontrollable Fe3O4nanoparticles were synthesized via oxidation precipitationmethod. A novel magnetic composite material was successfully synthesized bycombining Fe3O4nanoparticles and activated carbon-Fe0, and further used as aheterogeneous Fenton catalyst for the degradation of simulation wasterwater(Rhodamine-B) and practical coking wasterwater. The preparation of catalysts, the bestreaction conditions and the reaction mechanism were studied in this research. Thestudy is briefly summarized as follow:（1）The effect of preparation conditions of oxidation precipitation method on thecatalytic performance of Fe3O4nanoparticles wereinvestigated. The result shows thatthe Fe3O4nanoparticles with higher catalytic performance were synthesized at thefollowing conditions: Fe2+concentration of0.4mol·L-1, reaction temperature95℃,Fe2+, NO3-and OH-mole ratio of2:1.5:4and reaction time2h via positiveprecipitation.（2）The catalysts were characterized by SEM and XRD, which showed that thesize and morphology controlled Fe3O4nanoparticles could be prepared via oxidationprecipitation method. Different morphology, such as octahedron, hexahedron,polyhedron and sphere, and particle size of30nm and19nm of Fe3O4nanoparticlescould be obtained by controlling the preparation conditions. The catalytic tests showedthat the Fe3O4nanoparticles with sphere shape and smaller particle size are of bettercatalytic performance.（3）Controllable magnetic composites C/Fe0/Fe3O4was prepared through in situsynthesis method using activated carbon/Fe0as support. The obtained materials werecharacterized by SEM and XRD, which showed that the Fe3O4nanoparticles could be well immobilized on activated carbon/Fe0. The optimum mass ratio of activated carbon,Fe0and Fe3O4was0.5:3:1. The removal rate of Rhodanmine B in the present ofC/Fe0/Fe3O4in90min was close to100%when the initial conditionswere T=15℃,[catalyst]=1.0g·L-1, pH=3.0and [H2O2]=50mmol·L-1.（4）The controllable magnetic composites were applied to advanced treatment ofpractical coking wastewater. The results show that the CODCrof wastewater in10hcould reduce to58.2mg·L-1and chroma could be reduced below20at the followinginitial conditions: T=15℃,[catalyst]=1.0g·L-1,[H2O2]=20mmol·L-1and pH=3.0. Theeffluent quality met the recycled water standards of GB/T19923-2005. The materialsprepared with activated carbon or coke are of better catalytic performance than that ofpulverized coal injection coal. The catalytic performance of the material decreased incycle experiments due to the loss of a small amount of Fe.