Elizabeth Mendes de Oliveira

Application of Nanoparticle Tracking Analysis (NTA) in Aqueous Solutions of TiO2

The study of nanoparticles involves a new field of research in various areas of technology, whose production and use have been recognized as multiple benefits to the society. However, the uncontrolled emission to the environment of nanoparticles is growing exponentially over the last decade. Thus, knowledge of the influence of nanoparticles and how they can modify the ecosystem is extremely importantand demand specific studies. Therefore, it is of fundamental importance to increase the knowledge of the interactions and transport of nanoparticles in soil, in particular this research will study the TiO2 nanoparticles (TiNPs). Aiming to improve such knowledge, this paper addressed tests on columns with soil collected in the landfill Volta Redonda located in the state of Rio de Janeiro, Brazil. Aliquots of TiO2-nanoparticle suspensions in soil were collected periodically after their preparation, and analyzed the aggregate of particles distribution and Ti concentration. Experimental results suggest that the higher stability of TiO2 suspensions resulted in a higher mobility of TiO2 through soil layers with lower retention rate.

Effects of the silica nanoparticles (NPSiO2) on the stabilization and transport of hazardous nanoparticle suspensions into landfill soil columns

This study evaluates the stability and transport behaviors of hazardous nanoparticles into soil landfills using experimental procedures to simulate the effects of natural silica nanoparticle suspensions during their percolation into the soil layers of municipal waste landfills. For this, we prepared stabilized suspensions of nanoparticle oxides containing silicon (NPSiO2), titanium (NPTiO2), copper (NPCuO) and zinc (NPZnO), which are recognized as hazardous to the environment, and we conducted leaching experiments within the soil column by simulating landfills layers and simulating the capture and attenuation of nanomaterials into municipal waste landfills. The results demonstrated that the presence of NPSiO2 in suspensions increases the stable concentrations of copper, zinc and titanium oxides and strongly decreases soil layer effectiveness. In contrast, NPZnO improves effectiveness due to its ability to promote agglomeration and setting conditions, allowing further complexation.

Study of the Effects of SiO2 Nanoparticles Concentration on the TiO2 Nanoparticles Suspensions Stabilization

TiO2 nanoparticles (NPTiO2) suspensions are in several ecosystems and residue treatment processes or disposal systems due to their large industrial use and handling. The interactions of the NPTiO2 with NPSiO2 have special interest due to their strong ability to maintain high TiO2 nanoparticles concentration in suspension and promote nanoparticles clustering. These characteristics are used either in cleaning systems or in production of nanoparticles solution for several applications in the food industry or medicine. In this study, suspensions of NPTiO2 and NPSiO2 are synthetized and their stabilizations are discussed. A base TiO2 nanoparticles suspension was synthetized and the initial concentrations of SiO2 nanoparticles (NPSiO2) were changed in order to determine the effects of presence of SiO2 nanoparticles on the stabilization and clustering size. Zeta potential and concentrations measurements were carried out throughout the time and correlated with the initial concentrations of the base suspensions. In this study, the concentrations, zeta potential and pH are measured to estimate the stability of the suspensions. The clustering size, obtained by nanoparticle tracking analysis (NTA), are also monitored and discussed. Results of column soil experiments are discussed and compared under similar conditions with literature data.

Analysis of the Microwave Heating Effect in the Comminution Efficiency of Iron Ore Particles

Heating iron ore fine particles using microwave energy has been effective due to the different interactions between minerals and gangue in the magnetic field generated by the microwave. In this way, this paper proposes to use microwave energy to heat the particles of iron ore to promote micro cracks and fissures, which would facilitate the comminution and pulverization process to produce pellet feed. It was analyzed different conditions of heating and cooling in the comminution step. By using techniques of scanning electron microscopy (SEM) and image analysis it was possible to assess and quantify the micro cracks and subsequent analysis of the energy and size fragmentation in the comminution step of ultrafine particles.