Pyrite utilization in the carboniferous region of Santa Catarina, Brazil : potentials, challenges, and environmental advantages

The main coal seams explored in the coal region of Santa Catarina are Barro Branco (BB) and Bonito (BO). Owing to the association with the mineral matter, the tailings generated in the beneficiation are arranged in disposal areas, and subject to the generation of acid mine drainage (AMD). The objective of this study was to evaluate the use of pyrite present in the coal rejects of the BB and BO seams and the environmental gains with desulfurization. For this purpose, densimetric separability test, ash, sulfur, and AMD generation analyses were performed. In addition, the amount of pyritic concentrates and sulfuric acid were estimated considering the current level of production. Three densimetric fractions were obtained: less than 2.2 (energetic material), between 2.2 and 2.7 (low sulfur material), and greater than 2.7 g cm-3 (pyrite concentrate). The results revealed that the two seams could be beneficiated by gravimetric processes, obtaining pyrite concentrates with approximately 60% pyrite. By converting pyrite to sulfuric acid would represent an increase of 500,000 tons per year in the Brazilian production of this material and, in environmental terms, a reduction of up to 90% of the acidity potential to be disposed in the environment in the case of the BB seam and 65% for the BO seam. It was also observed that the “desulfurized” fraction of the BO had higher levels of pyrite and a higher potential for acidity generation than the BB seam, implying greater risks of environmental contamination and higher acid water treatment costs

Hydrometallurgical processing of Brazilian iron ore tailings for the synthesis of pigments

The aim of this study was to investigate the synthesis of iron oxide pigments from IOT. The sample of IOT was obtained through mining activity of the Quadrilátero Ferrífero in the state of Minas Gerais, Brazil. The procedure was carried out by hot acid leaching with hydrochloric acid (HCl) which allowed the recovery of about 95% of the iron in a liquor. The iron-based pigments— red (IBP_R), black (IBP_B), and yellow (IBP_Y)—were synthetised from the liquor by selective precipitation, crystallisation, and thermal procedures. The pigments were characterised by particle size distribution, mineral and chemical compositions, as well as colourimetric properties. The process of synthesis was successful and the procedure was shown to maximise the utilisation of mineral resources and minimise the environmental, social, and economic impacts associated with IOT disposal

Heterogeneous photocatalytic degradation of dyes in water/alcohol solution used by the brazilian agate industry

The agate dyeing industry has been commonly seen as a high-pollution industry. Dyeing wastewater treatment is considered one of the most important categories for water-pollution control, because of its intense colour and the high concentration of organic contaminants. Most dyes used in the process present minimal biodegradability due to aromatic organic compounds in their structure. Using a photocatalytic reactor, experiments were carried out to study the decolorization of a water solution containing 8% ethylic alcohol and 200 mg L−1 of the dye Rhodamine B (RhB), the most difficult colorant to degrade among the used by the agate industry. The best conditions were further applied to treat the same agate water/ethyl alcohol solution containing a mixture of 200 mg L−1 of Rhodamine B (RhB), Crystal Violet (CV), Brilliant Green (BG), and Blood Red (BR). All the experiments were performed in a 2 L reactor equipped with ultraviolet (UV) lamps, at a wavelength of 365 nm, with powdered TiO2 or ZnO as the catalyst. The results indicated that the optimal decolorization conditions were attained with 2.5 g L−1 of the catalyst at pH 10 and an irradiation time of 80 min. The process resulted in complete degradation of CV, BG and 80% - 90% degradation of RhB and BR. The catalyst ZnO presented a performance somewhat better than TiO2. It is possible to conclude that the process of heterogeneous photocatalysis is effective for decolorization of water streams from the agate industry

Plantas aquáticas secas : uma alternativa moderna para remoção de metais pesados de efluentes industriais

O presente trabalho mostra o potencial de aplicação da biomassa seca e morta de plantas aquáticas na remoção de metais pesados de efluentes industriais. Dados referentes as caracteristicas dos tecidos vegetais das espécies Potamogeton lucens. Salvinia sp. e Eichornia crassipes e como ocorre a interação com os metais são apresentados. Adicionalmente, os resultados obtidos no tratamento de um efluente de galvanoplastia em uma coluna de percolação em escala piloto preenchida com uma mistura das biomassas das plantas P. lucens e Salvínia sp. são reportados. A eficiência do processo foi medida em relação a remoção dos metais cobre. zinco. niquel e ferro. Os resultados mostram que a alternativa estudada é eficiente na remoção de metais presentes de forma residual em efluentes da indústria metal-mecânica.The present work shows the potential use of the non-living biomass,of aquatic plants for the removal of heavy metal ions from Waste waters. It is reported the main characteristics of the plant tissues of the species Poramogeron lucens, Salvinia sp·, and Eichhornia crassipes and the mechanis of metal binding. Additiolly, the results obtained in the treatememt ofm electroplanting wastewater in a packed bed column filled with a mixture of P.Lucens ,and Salvinia sp· biomasses are showen. The process efficiency was evaluated in terms of copper, zinc, nickel and iron removed. The results show that the process studied is efficient for the removal of residual concentration of heavy metal present in waste waters from metalfinishing industries

Using static, kinetic and metal mobility procedures to evaluate possibilities of coal waste land disposal at Moatize Mine, Mozambique

Coal mine waste rocks produced during mining and beneficiation can affect the environment due to land degradation and acid mine drainage generation. However, proper characterization and treatment of mineral processing wastes creates options for safe disposal, enhancing the environmental performance. The aim of this study was to use static and kinetic tests to assess properties of coal waste produced at the Moatize Mine in Mozambique, one of the largest "world-class" coal deposits. The study included sampling and characterization of coarse and fine wastes generated during coal beneficiation. Both materials were analyzed in terms of granular properties, static procedures - immediate composition, sulfur forms, mineralogical composition, elemental composition, acid-base balance – and kinetic behavior in humidity cell tests. The conjugation of these techniques indicates that these wastes have a low water acidification potential and low geochemical mobility of toxic elements. Therefore, it was concluded that fine and coarse wastes could be used in land shaping procedures

Removal of pollutants from an AMD from a coal mine by neutralization/precipitation followed by “in vivo” biosorption step with the microalgae Scenedesmus sp.

This work evaluates the benefits of a complementary treatment step of acid mine drainage (AMD) using the algae Scenedesmus sp. in terms of algae biomass production, residual metal removal, and the toxicity of the discharged water. Conventional treatment by neutralization/precipitation of an AMD from a coal mine in Brazil was conducted with Ca(OH)2 at pH 8.7. Algal growth studies were performed in the treated AMD, with and without a nutrient supply. The raw e uent and treatments were compared in terms of residual concentration of metals and sulfate, conductivity, and toxicity with the Allium cepa and Daphnia magna test organisms. The results show that the conventional treatment allowed a major metal removal, reduction in the conductivity, and good indices in the toxicological parameters evaluated. The biosorption with in vivo microalgae improved the quality of the e uent for residual metals. No significant toxicity was observed to Allium cepa in all treatments performed, while the Daphnia magna test indicated a reduction in toxicity after the biosorption step. It was concluded that algae growth can be carried out in treated mine waters, providing algae biomass and helping to achieve the standards for water discharge

Waste generation in agate processing : use of SiO2 as a support material for Fe3O4

Brazil is one of the main producers of colored gemstones, and Rio Grande do Sul is the state with the greatest production of agates, amethysts and citrines. This sector is preponderant in the economy of the regions of the Upper Uruguai and Middle Plateau, but it faces technological difficulties, among which we can highlight the large volume of gemstones exported in rough state, with low added value, and the low efficiency equipment. Another problem is the sheer volume of waste generated without the adequate treatment and appropriate place for disposal. The purpose of this study is to conduct a diagnosis of the processing of the gems, identify the types of waste generated and the importance of the implementation of environmental management for this industrial sector and propose an alternative of SiO2 use (a residue from the processing of Agates) as a support material for the compounds based on iron oxides

Prevenction of the acid mine drainage (AMD) by blending coal tail and a slag from an eletric steel plant

Uma das tecnologias de prevenção da geração da Drenagem Ácida de Minas (DAM) é o método de aditivos alcalinos. A alcalinidade impede as reações de oxidação da pirita, evitando a geração de acidez e a solubilização de metais em meio aquoso. Assim, o objetivo deste trabalho é estudar o uso de escória do forno panela de aciaria elétrica como aditivo alcalino para o controle da geração de DAM. O rejeito de carvão foi obtido em uma mina de carvão do Estado do Rio Grande do Sul e a escória foi fornecida por uma usina siderúrgica semi-integrada. Inicialmente, caracterizaram-se os materiais pelo método de contabilização de ácidos e bases. Após, realizaram-se ensaios cinéticos em células úmidas pelo método ASTM D 5744-96. A qualidade da água de percolação nas células úmidas foi analisada em termos de pH, Eh e concentração de metais e sulfatos. Os resultados demonstram que a DAM pode ser evitada pela mistura do rejeito de carvão com a escória em uma proporção de 3:1. Pode-se concluir que a disposição conjunta de escória de aciaria com rejeito de carvão é uma alternativa viável para o controle da geração de DAM em minerações de carvão.Alkaline additive is an effective method for controlling acid mine drainage (AMD). Alkalinity hinders pyrite oxidation reactions, avoiding acidity and metals solubilization in water. Thus, the aim of this work is to study the use of a ladle furnace slag as an alkaline additive for controlling AMD. The coal tailing was obtained from a coal mine in Rio Grande do Sul State and the slag from a minimill steel plant. Initially the materials were characterized by the acid-base accounting method. After, kinetic tests in humidity cells were carried out according to ASTM D 5744-96 method. The leaching water was evaluated in terms of pH, Eh, metals, and sulfates concentration. The results showed that AMD could be avoided by mixing the coal’s tailings with slag at 3:1 proportion. It is demonstrated that ladle furnace slag is a suitable alkaline material for AMD prevention in coal tailings deposits

Biossorção de metais pesados com a biomassa de macrófitos aquáticos

O presente trabalho tem como objetivo estudar a biomassa seca e homogeneizada de macrófitos aquáticos como um material sorvente de metais pesados (Cr(III), Ni, Cu, Zn, Cd e Pb) presentes em soluções aquosas. Os macrófitos aquáticos foram coletados em recursos hídricos do Estado do Rio Grande do Sul, lavados, secos a 60°C, moídos, peneirados e embalados em sacos plásticos. Diversas propriedades físicas, bioquímicas, interfaciais e químicas dos biossorventes foram analisadas. Realizaram-se estudos de sorção em batelada com soluções sintéticas de metais pesados e, posteriormente, estudos em coluna de percolação de laboratório com soluções sintéticas e efluentes industriais de atividades de mineração e metalurgia. A sorção dos metais pesados por macrófitos aquáticos não ocorre necessariamente por processos metabólicos da planta viva. A biomassa morta de algumas espécies acumula elevadas quantidades de metais por mecanismos físico-químicos. Dentre as espécies estudadas, o Potamogeton lucens é a que apresenta maior capacidade de sorção de metais pesados. As espécies Salvinia herzogii e Eichhomia crassipes também apresentam-se eficientes. A sorção dos metais ocorre por reações de troca iônica, onde o principal grupo superficial envolvido é o carboxila. O fenômeno segue o modelo de adsorção de Langmuir e os valores máximos de acumulação foram de 1,5 meq/g para o P. lucens, 0,9 meq/g para a S. herzogii e 0,7 meq/g para a E. crassipes. A sorção dos metais pesados é máxima em valores de pH acima de 5,0. O limite na faixa básica é dado pelo pH de precipitação dos elementos metálicos na forma de hidróxidos. A seguinte ordem de seletividade foi determinada para alguns dos cátions estudados: Cu+2 > H+> Zn+2 > Ni+2 > Ca+2 >Na+. A remoção dos metais pesados pode ser eficientemente realizada em colunas de percolação com leito empacotado. Após a saturação, os metais podem ser recuperados e a biomassa regenerada por eluição com soluções ácidas (por exemplo: 0,5 a 2% HCl). A biomassa dos macrófitos aquáticos mostrou-se efetiva no tratamento de efluentes de galvanoplastia e de mineração como um estágio de polimento. Em certos casos, após vários ciclos de sorção/dessorção, os biossorventes regenerados e neutralizados podem ser destinados à alimentação de animais. A calcinação dos biossorventes saturados com metais pesados permite obter concentrados de interesse metalúrgico. A alternativa tecnológica estudada é eficiente no tratamento final de efluentes líquidos contendo concentrações residuais de metais pesados. As principais vantagens deste processo são a alta cinética, a seletividade para a remoção de metais de transição e o baixo custo. Os resultados são discutidos em termos das propriedades superficiais dos biossorventes, química da solução aquosa, parâmetros termodinâmicos e cinética do processo.The aim of this work was to study the dried and homogenized biomass of aquatic macrophytes as sorbent materiais for heavy metais (Cr(III), Ni, Cu, Zn, Cd and Pb) present in aqueous solutions. The aquatic macrophytes were collected in Rio Grande do Sul - Brazil, washed, dried at 60°C, ground in a bladed mixer and stored in plastic bags. Several physical, biochemical, interfacial and chemical properties of the biosorbents were analyzed. Sorption studies were carried out by batch procedures with synthetic solutions containing heavy metais. Additionally, sorption studies in a laboratory packed bed column with synthetic solutions and real efiluents from mining and metallurgical industries were performed. The results showed that it is not necessary the macrophytes be alive to remove heavy metais from aqueous solutions. The nonliving biomass of some species binds heavy metais by physico-chemical mechanisms. From the macrophytes studied, Potamogeton lucens showed the highest uptake capacity. The species Salvinia herzogii and Eichhornia crassipes also present a high capacity of heavy metal accumulation. The sorption mechanism by these biomaterials was found to occur mainly by an ion exchange reaction between dissolved metal ions and the carboxylic groups present on the plant surface. Sorption followed the Langmuir adsorption isotherm and maximum metal uptake was attained at 1,5 meq/g for P. Lucens, 0,9 meq/g for S. herzogii and 0,7 meq/g for E. crassipes. Maximum metal removal was obtained at pH higher than 5, O. The basic limit was given by the precipitation pH o f the heavy metais as hydroxides. The selectivity order o f sorption was determined as: Cu+2 > H+ > Zn+2 > Ni+2 > Ca+2 > Na+. Heavy metal removal can be efficiently carried out in packed bed columns. After sorbent saturation, metal ions can be recovered from the loaded biomass by elution with HCI solutions (for example: 0,5 a 2% HCI). Practical studies showed that this process is efficient for the treatment of electroplating and mining effluents as a polishing stage. In some cases, after several sorption/desorption cycles, the regenerated and neutralized biosorbents can be used for animal feeding. The calcination of the biosorbent loaded with heavy metais allowed to obtain a metal concentrate of metallurgical degree. The biomaterials studied are suitable for the final treatmet of liquid efiluents containing residual amounts of heavy metais. The main advantages of the process are the kinetics, the selectivity for transition metais and the low cost of the biosorbents. Results are discussed in terms of the surface properties of the materiais, solution chemistry, thermodynamic parameters and kinetic data