Abstract In this article, we present the results of the mineralogical quantification of airborne dust from an urban area located in the Brazilian state of Minas Gerais in the vicinity of a gold mine. Three samples were collected at different points to assess spatial consistency. Results showed that the mineralogy, in relation to both major minerals and accessory minerals, is very similar for all samples, being predominantly composed of muscovite and quartz, which together account for around 60% to 75% by weight. The accessory minerals are clinochlore, albite, dolomite, calcite and kaolinite and the averages for each range from 4% to 13%. The only trace mineral with concentration below 1% was pyrite which has a concentration below 1%. The results provide an indication that the mining area is not the sole source of local dust, although the mine's contribution is significant.

The introduction of magnetic properties in adsorbent materials has the aim of improving solid-liquid separation processes. In this work, a magnetic composite was synthesized through the precipitation of manganese oxide in the presence of magnetite particles using O2 as an oxidant. The composite proved to be chemically and physically stable within a wide range of pH values. The composite characterization indicated that hausmannite (Mn3O4) represents the precipitated manganese phase and that magnetite undergoes no phase transformation during the synthesis. The composite and Mn3O4 particles were used to remove As(III) from aqueous solutions. The magnetic composite and Mn3O4 sample presented high and similar affinity for As(III), with maximum sorptive capacities of 14 mgAs g solid-1 (0.0048 mmolAs m-2solid) and 20 mgAs g solid-1 (0.0049 mmolAs m-2solid), respectively, at pH 5.0. The combination of an active high surface area sorbent (Mn3O4) with a magnetic phase (Fe3O4) allows for efficient As(III) removal and solid/liquid separation.

This work describes the process for functionalization of laponite through the grafting of 3-mercaptopropyltrimethoxysilane (MPTS). Laponite is synthetic smectite clay with surface area of 350 m²/g. The samples, prior to and after functionalization, were characterized by chemical analyses, thermogravimetric analysis (TGA), x ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), scanning electron microscopy and energy dispersive spectrometry (MEV/EDS). Infrared spectroscopy and elemental analyses confirmed the presence of organic chains and thiol groups in the modified clay. The immobilized and available thiol group, measured according to the Volhard method, totaled 1.4 meq/g of clay, with approximately 90% accessible for Ag+ trapping. These results represent an improvement as compared to other works concerning the functionalization of smectite-type clays in which the effect produced by functional group blockage limits the access of species to less than 10% of the complexing sites.

Esse trabalho tem como objetivo avaliar o potencial de geração de Drenagem Ácida de Rocha (ARD) de duas amostras de minério de ouro sulfetado através de três das mais tradicionais técnicas de diagnóstico de ARD: "Standard Acid Base Accounting and Modified Acid Base Accounting", métodos estáticos, e células úmidas, método cinético. As amostras foram submetidas a uma caracterização química e mineralógica que indicou a presença de traços de sulfetos, tais como pirita, arsenopirita e pirrotita e de carbonatos, tais como calcita e dolomita. Considerando os resultados dos ensaios realizados, foi confirmada a necessidade de se utilizarem diversas técnicas para se concluir sobre o potencial de geração de ARD dessas amostras. Enquanto os resultados dos ensaios do "Standard ABA" foram inconclusivos, os resultados de NNP e NP/AP do "Modified ABA" indicaram uma tendência de as amostras TP01 e WP01 serem geradoras de ácido, sendo essa tendência discretamente mais acentuada para WP01. Assim, o ensaio cinético foi conduzido para elucidar os resultados. Os resultados das células úmidas para as amostras TP01 e WP01 indicaram a provável oxidação dos sulfetos resultando na produção de ácido, seguida de neutralização pela alcalinidade gerada pelos carbonatos. Com base nesses resultados, pode ser concluído que, apesar de a amostra WP01 apresentar um potencial de geração de ARD ligeiramente superior a TP01, essas amostras podem estar em diferentes estágios no processo, ou melhor, TP01 deve estar em um estágio de geração de ARD mais avançado que WP01. O papel fundamental dos ensaios cinéticos foi ressaltado pelos resultados.

This work is aimed at evaluating the potential of Acid Rock Drainage (ARD) from two Brazilian gold sulfidic ore samples, by means of using three of the most traditional ARD prediction techniques: Standard Acid Base Accounting and Modified Acid Base Accounting, as static methods, and humidity cells, as a kinetic method. Samples were submitted to chemical and mineralogical characterization that indicated the presence of traces of sulfide minerals, such as pyrite, arsenopyrite, pyrrhotite and of carbonates, calcite and dolomite. While the Standard ABA results were inconclusive, the Modified ABA NNP results and NP/AP ratio suggested a tendency of TP01 and WP01 being acid generators, this tendency being slightly stronger for sample WP01. So, a kinetic test was conducted to elucidate the results. The humidity cells results for samples TP01 and WP01 indicated the probable sulfide oxidation to produce acid, subsequently neutralized by alkalinity generated by the carbonates. Based on the results, one can conclude that although sample WP01 has a slightly higher ARD generation potential than TP01, these samples can be at different stages of ARD process, or better, TP01 is at a more advanced stage of ARD production than WP01. The determinant role of the kinetic tests is highlighted by the results.