Both synthesis and photocatalytic potential of an innovative catalyst-powder type composite material based on the Zn or/and ZnO dispersed in a matrix of amorphous-carbon have been investigated. Zn/ZnO/amorphous-carbon nanostructured-matrix composite was prepared by partial pyrolysis method based on the Pechini method. The amorphous character of composite was characterized X-ray diffraction, while chemical bond investigated by infrared spectroscopy. The photocatalytic activity directed to the degradation of the phenol red dye of small fraction of commercial ZnO, Zn/C and Zn/ZnO/C composites were evaluated as a function of the degradation reaction of the phenol red dye, in the alkaline medium pH = 9. A mass concentration of 1:10,000 was selected being considered 30 and 150 min of reaction A comparison between photocatalytic activity showed that the degradation rate of phenol red dye is more efficient at both ZnO/Zn/C and Zn/C amorphous composites when compared to the pristine ZnO. The efficiency obeys the following order C/Zn ≥ C/ZnO/Zn > commercial ZnO with conversion equal to 70% for C/Zn and C/ZnO/Zn, while for the ZnO is around 55%. The kinetic of degradation is discussed.

urface properties core/shell nanoparticles have been investigated in recent years due to their promising reactivity in catalysis surface. In this work, the ZnO@Cr core/ shell nanoparticles were synthesized by Modified Pechini method and characterized by X-ray diffraction and scanning electron microscopy (SEM). The structural parameters were evaluated as a function of chromium coatings on the ZnO structure, using the Rietveld method. From the refinement of experimental diffractogram determined the crystallographic structure of the investigated system as being of the hexagonal type with space group P63mc. The coating of ZnO with chrome led to an increase of the structural parameters. Photocatalytic activity of ZnO@Cr nanoparticles was studied using a low power reactor and the phenol red dye in acid and basic medium. The nanoparticles showed level of degradation in acid medium 1.24 times higher than that in basic medium. The photodegradation follows a first order kinetics.

Characterization of membrane pore size by experimental methods is usually done by the determination of the rejection of polymeric molecules having a range of sizes such as PEG. These experiments are affected by concentration polarization, which can lead to erroneous interpretation of the results, mainly because the concentration and the permeate flux change along the membrane surface. Additionally, experimental methods alone are insufficient to obtain the membrane pore size. To improve the current approach, numerical methods are used to understand mass transport limitations in rejection experiments and to predict the membrane pore size. In the current study, the results show that the ultrafiltration membrane has a MWCO of 20 kDa, different from the value set by the manufacturer (30 kDa). For the experimental conditions, concentration dependent viscosity and osmotic pressure do not influence the permeate flow rate or rejection. Moreover, the membrane pore size was found to be 2.59 nm. This value was determined comparing rejection values obtained by numerical and experimental results. Numerical analysis is also important to characterize the flow and mass transport in each point at membrane surface.

Organic/inorganic hybrids composites type have been reported as an alternative for the preparation of multifunctional materials with superior properties to those of individual constituents. In this work, hybrid composites of semiconductor oxides with amorphous carbon (C/ZnO and C/TiO2) were synthesized by partial pyrolysis method and characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The XRD patterns showed the presence of crystalline diffraction lines overlaid by diffraction halos. Infrared spectra showed bands associated to the stretching of Zn-O and Ti-O bonds, as well as bands assigned to the stretching vibrations of C-O, C=O and C-H. Micrographs showed the formation of organized structures in the shape of plates and agglomerates of particles. Structural characterizations showed that the composites present the characteristics of the pristine semiconductors as well of the amorphous carbon matrix, showing a great synergism between C/semiconductor.

The control of environmental pollution has led to an intensive search for innovative and efficient technologies for wastewater treatment, especially those with toxic or non-biodegradable compounds. In this sense, this work involved the preparation of a hybrid composite of TiO2 with amorphous carbon by partial pyrolysis method and the analysis of their photocatalytic potential using phenol red dye as a test molecule. The composite was characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The evaluation of morphology and the structural characterization of the powder confirmed the formation of the hybrid composite of TiO2 dispersed in a carbon matrix with turbostratic structure, organized in the shape of overlapping plates. The composite presented a discoloration rate of 67% after 4 hours of irradiation. The photocatalytic reaction follows a kinetics of first order type.