The mineral waste studied was host rock from a chromite mine located in Andorinha/Bahia, extracted and stockpiled in yards without specific application. Host rock was submitted to chemical analysis, XRD, SEM-EDS, IR and TGA and classified according to ABNT standards for solid waste classification. Analyses confirmed that this host rock, classified as ultrabasic, consists mainly of dolomite, calcite and diopside. Hazard assessment results showed this host rock should be classified as class II B - inert waste, important for its potential application in agriculture as a soil acidity correction agent.

Samples of Kaolin from different regions in Brazil were characterized by XRD, SEM and chemical analysis. A chemical bleaching study with pH adjustment was accomplished with the fractions below 37 μm, after classification by screening. The main objective was to evaluate the conditions of chemical bleaching that most increase the brightness of these kaolin's samples. Increases between 2.63 and 2.98% in the brightness (ISO) were observed after the chemical bleaching. We could say that the reduction of Fe3+ to Fe2+ during the chemical bleaching promoted an increase in the brightness, based on the Pourbaix Diagrams.

Esse trabalho apresenta uma proposta para efetuar, em escala de laboratório, a separação do epídoto presente em estéreis da lavra de scheelita da Província da Borborema. Para tanto, um fragmento de rocha foi britado e classificado em três faixas granulométricas, entre 150 µm e 600 µm. A concentração do epídoto foi realizada em mesa vibratória, seguida de separação magnética usando o separador isodinâmico Franz. As frações magnética e não-magnética foram analisadas por difratometria e espectrometria por fluorescência de raios X. Para a faixa de 150 a 300 µm, foi possível efetuar a concentração do epídoto com um teor de 75% após quatro passagens pelo separador magnético usando correntes de 0,5 e 0,6 A, correspondendo a 0,5 e 0,6 T, respectivamente. Constatou-se que a fração de maior susceptibilidade magnética é constituída de andradita e que os principais contaminantes do concentrado de epídoto são a calcita, a andradita e o quartzo.

This paper presents a laboratory procedure to concentrate epidote from fragments associated with country rocks of the scheelite mineralization in the Borborema Province (Rio Grande do Norte, Brazil). A block weighting 17.5 kg was crushed and classified in grain sizes ranging from 150 to 600 µm. The concentration was carried out in a shaking table followed by four cycles of magnetic separation using a Frantz isodynamic separator with currents ranging from 0.5 and 0.6 A (0.5 to 0.6 T). The mineralogical characterization of the pre-concentrate and the fractions resultant from magnetic separation were carried out by X-ray powder diffractometry and X-ray fluorescence spectrometry. The separation of the epidote allowed close to 75% epidote for the 150x300 µm size class. The fraction with the highest magnetic susceptibility in the mineral assemblage was mainly composed of andradite. Calcite, andradite and quartz were found to be the contaminants within the concentrate.

Neste artigo, o potencial no qual a depressão da galena ocorre, é relacionado com a formação de compostos hidrofílicos em sua superfície. São propostas reações com base em voltametria cíclica, dados termodinâmicos e análises por espectroscopia de fotoelétrons. Variáveis eletroquímicas, tais como o potencial de oxirredução, apresentam boas perspectivas para a flotação seletiva da galena e esfalerita, pois numa dada faixa de potencial, a superfície da galena, ao contrário da esfalerita, se torna hidrofílica, conforme mostraram as medidas de ângulo de contato e testes de microflotação.

In this article, the potential at which galena depression occurs is related to the formation of hydrophilic compounds on its surface. Reactions are proposed based on analyses by cyclic voltammetry, thermodynamic data, and X-ray photoelectron spectroscopy (XPS). Electrochemical variables, such as the redox potential, present good perspectives for selectivity in the flotation of galena and sphalerite, because in a given range of potentials, the galena surface becomes hydrophilic, as shown by measurements of the contact angle and floatability tests.