Dispersibility, Shape and Magnetic Properties of Nano-Fe₃O₄Particles

Nano-Fe3O4 particles were prepared by a two-step microemulsion method, the influence of molar ratio of water to NP-5 (R), alkali concentration and temperature on dispersibility and shape of the nanoparticles were discussed. Magnetic studies were also carried out using VSM in this paper. It was found that the optimum preparation parameters are R = 6.0, alkali concentration = 2.5 mol.L–1, initial total iron concentration as 0.88 mol.L–1, and the temperature being 30°C, the prepared nano magnetite particles have uniform size and good dispersibility with a crystal structure belonging to cubicFe3O4 and lattice parameters of a = 8.273 ?. The results of magnetic studies show, magnetic properties of particles are influenced by dispersibility of nanoparticles which depends on size of clusters. The better dispersibility of nanoparticles leads to more ordered inner magnetic vector, and so the stronger magnetic behavior of nano-Fe3O4 particles.

Degradation of 2,4-dichlorophenol catalyzed by the immobilized laccase with the carrier of Fe_3O_4@MSS–NH_2

With the Fe3O4@MSS(magnetic mesoporous silica spheres)–NH2as the carrier and the glutaraldehyde as crosslinking agent,the immobilized laccase has been prepared and characterized by XRD,IR,SEM and BET etc.Under the optimal conditions,the removal efficiency of2,4-DCP reached 88%and the removal efficiency still remained 61.5%after five cycles of operations.In virtue of GC–MS analysis,2,5-dimethoxyl-1,4-quinone,2-chlorine-1,4-dimethoxyl benzene,3,30-dichlorine-4,40-dimethoxyl biphenyl,maleic acid phenol ester,and three kinds of maleic acid,alcohol ester,and para-hydroxyl phenol ester compounds have been identified as intermediate and final degradation products of 2,4-DCP,respectively.Besides,the degradation products of 2,4-DCP have been confirmed by performing the1H-NMR and13C-NMR experiments,further demonstrating the degradation mechanism of 2,4-DCP by the immobilized laccase.

Cagelike mesoporous silica encapsulated with microcapsules for immobilized laccase and 2,4-DCP degradation

In this study,cage-like mesoporous silica was used as the carrier to immobilize laccase by a physical approach,followed by encapsulating with chitosan/alginate microcapsule membranes to form microcapsules of immobilized laccase based on layer-by-layer technology.The relationship between laccase activity recovery/leakage rate and the coating thickness was simultaneously investigated.Because the microcapsule layers have a substantial network of pores,they act as semipermeable membranes,while the laccase immobilized inside the microcapsules acts as a processing plant for degradation of2,4-dichlorophenol.The microcapsules of immobilized laccase were able to degrade 2,4-dichlorophenol within a wide range of 2,4-dichlorophenol concentration,temperature and p H,with mean degradation rate around 62%.Under the optimal conditions,the thermal stability and reusability of immobilized laccase were shown to be improved significantly,as the removal rate and degradation rate remained over 40.2% and 33.8% respectively after 6 cycles of operation.Using mass spectrometry（MS） and nuclear magnetic resonance（NMR）,diisobutyl phthalate and dibutyl phthalate were identified as the products of 2,4-dichlorophenol degradation by the microcapsules of immobilized laccase and laccase immobilized by a physical approach,respectively,further demonstrating the degradation mechanism of 2,4-dichlorophenol by microcapsule-immobilized laccase.