Aspectos eletroqu?micos na flota??o de sulfetos de zinco-chumbo presente em min?rio silicatado brasileiro ? uso do Na2S como modulador.

Sodium sulfide plays a multifunctional role in sulfide minerals flotation. The restorative action of minerals surface is its main function. As pH regulator, it reacts on surface and provides the conditions for interactions between minerals-collectors. However, changes in pulp composition can affect the electrochemical conditions desirable for flotation. Thus, the purpose this study was the evaluation of electrochemical state established in flotation, involving a willemite ore bearing zinc and lead sulfide minerals, when Na2 S was used as pH regulator. So, the electrochemical potential established in the pulp, the recoveries and contents of Zn, Pb, and Ag were considered as criteria for assessing the process. The pH equal to 9 yielded the best results for recovery (95.33% Zn; 61.24% Pb; 79.01% Ag) and content (12.96% Zn; 1.54% Pb; 307.33 ppm Ag), due to the smaller interference that occurred in the electrochemical conditions of systems when compared to pH 11, also included in the evaluations. However, larger dosages of Na2 S were counterproductive due to depressant action. Decrease in the potential can be related to the excessive amount of HS- , impairing the sulfides flotation.O sulfeto de s?dio possui um papel multifuncional na flota??o de minerais sulfetados. A restaura??o da superf?cie sulfetada dos minerais ? a sua principal fun??o. Como regulador de pH, este age na superf?cie mineral e oferece condi??es para as intera??es entre mineral-coletor. Contudo, mudan?as na composi??o da polpa podem afetar as condi??es eletroqu?micas necess?rias ? flota??o do sulfeto. Assim, o prop?sito deste estudo foi avaliar o estado eletroqu?mico estabelecido em flota??o, envolvendo um min?rio willem?tico portador de sulfetos de zinco e chumbo, quando o Na2 S foi usado como regulador de pH. Portanto, o potencial eletroqu?mico estabelecido na polpa mineral, as recupera??es e teores de Zn, Pb e Ag foram considerados como crit?rios para a avalia??o do processo. O pH igual a 9 permitiu os melhores resultados de recupera??o (95,33% Zn; 61,24% Pb; 79,01% Ag) e teor (12,96% Zn; 1,54% Pb; 307,33 ppm Ag), devido ?s menores interfer?ncias nas condi??es qu?micas do sistema quando comparado ao pH 11, tamb?m incluso nos par?metros de avalia??o. Contudo, maiores dosagens de Na2 S podem ter sido delet?rias como a??o depressora para os sulfetos. Quedas no potencial eletroqu?mico podem estar relacionadas ? quantidade excessiva de HS- , prejudicando a flota??o

Principal components analysis applied to flotation of iron ore.

A flota??o ? um processo de concentra??o, usualmente, empregado no beneficiamento do min?rio de ferro. O presente trabalho teve como objetivo avaliar a influ?ncia de vari?veis no processo de flota??o em bancada utilizando a t?cnica de an?lise de componentes principais. Para isso, realizou-se uma an?lise estat?stica com o aux?lio do software R, onde foram estudados os teores de s?lica e ferro na alimenta??o, no concentrado e no rejeito, teores dos contaminantes na alimenta??o (lama, ?xido de c?lcio e ?xido de magn?sio), perda por calcina??o e dosagem de amina. Por meio da an?lise foi poss?vel concluir que as duas primeiras componentes explicaram juntas aproximadamente 45% da variabilidade total da matriz de dados. A primeira componente explicou em torno de 25% da vari?ncia, sendo relacionada com a perda de seletividade do processo de flota??o. J? a segunda componente explicou cerca de 20% da vari?ncia e descreveu a inefici?ncia do processo. Atrav?s dos estudos realizados, foi poss?vel observar que a t?cnica de an?lise de componentes principais pode ser utilizada para melhor entendimento das vari?veis dos processos de flota??o em bancada.Flotation is a process of concentration, usually, employed in iron ore processing. The present work aimed to evaluate the influence of variables in the flotation process in the bench-scale using the principal components analysis technique. For this purpose, a statistical analysis by using the software R was carried out, studying the silica and the iron contents in the feed, in the concentrate and in the tailings as well as the contaminants (mud, calcium oxide and magnesium oxide) in the feed and also the loss on ignition and amine dosing. The analysis has allowed to conclude that the first two components together account for approximately 45% of the total variability of the data matrix. The first component explained about 25% of the variance, related to the loss of selectivity of the flotation process. The second component explained about 20% of the variance and described the inefficiency of the process. The conducted studies have shown that the principal components analysis technique can be used to a better understanding of the variables of the bench-scale flotation processes

Influence of attrition variables on iron ore flotation.

The presence of slimes is harmful to the flotation process: the performance and consumption of reagents are negatively affected. Traditionally, the desliming stage has been responsible for removing slimes. However, depending on the porosity of the mineral particles, desliming may not be sufficient to maximize the concentration results. An attrition process before the desliming operation can improve the removal of slime, especially when slimes cover the surface and/or are confined to the cavities/pores of the mineral particles. Attrition is present in the flowcharts of the beneficiation process of phosphate and industrial sand (silica sand). Research has been undertaken for its application to produce pre-concentrates of zircon and iron ore. However, there is still little knowledge of the influence of the attrition variables on the beneficiation process of iron ore. This study presents a factorial design and analysis of the effects of these variables on the reverse flotation of iron ore. The standard of the experimental procedures for all tests included the attrition of pulp, under the conditions of dispersion, desliming and flotation. The parameter analysed (variable response) was the metallurgical recovery in reverse flotation tests. The planning and analysis of the full factorial experiment indicated that with 95% reliability, the rotation speed of the attrition cell impeller was the main variable in the attrition process of the iron ore. The percentage of solid variables in the pulp and the time of the attrition, as well as their interactions, were not indicated to be significant

Utilising starches from sugarcane and cassava residues as hematite depressants.

The aim of this study is to investigate the actions of sugarcane bagasse and cassava wastewater (two residues from the food industry) when used as hematite depressants. Additionally, the effect of each residue preparation method on the flotation results was analysed. The efficiencies of the depressors were investigated through microflotation tests utilising samples of pure hematite and quartz from Quadril?tero Ferr?fero, which is in the state of Minas Gerais (Brazil). The pH of 10.5 was selected due to its frequent use in the concentration of iron ore via flotation in Brazil. Three residue gelatinisation methods (natural, heated, and conventional) were evaluated to determine the most efficient method for the flotation process. Further, zeta potential measurements were performed on the hematite to ascertain the performances of the residues. Microflotation test results showed that hematite recovery decreased with increasing depressant concentration, for all reagents. Finally, the actions of residues gelatinised with the addition of sodium hydroxide (i.e. the conventional method) were shown to be similar to that obtained from corn starch, which indicates their potential application in the flotation process

Estado de dispers?o de part?culas de hematita em polpas na presen?a de reagentes.

Os min?rios de ferro a serem explotados est?o com teores do mineral de interesse muitos baixos. Com a diminui??o desses teores, ocorre uma necessidade maior de moer o min?rio em granulometrias mais finas. Os ?xidos e hidr?xidos met?licos, tais como os ?xidos de ferro, tornam-se carregados quando dispersos em meio aquoso. As altera??es ocorridas na superf?cie de ?xidos e a forma??o de interface eletricamente carregada entre as part?culas e o meio aquoso s?o controladas pelo pH e for?a i?nica da solu??o em que s?o dispersos. Esses fatores levam ? necessidade de se estudar o efeito da dispers?o nas etapas de flota??o, espessamento e filtragem. Este trabalho, em escala de laborat?rio, visou contribuir para a melhor compreens?o do tratamento de min?rios de ferro abordando a dispers?o de polpas de hematita na presen?a de reagentes dispersantes ou agregantes. Foram avaliados quatorze reagentes org?nicos e inorg?nicos nos ensaios de dispers?o. O estudo da dispers?o da hematita sem adi??o de reagentes mostrou uma diminui??o do grau de dispers?o na faixa de pH de 6,5 a 7,5. As adi??es de amido e fub? levaram a agrega??o da hematita em toda faixa de pH, enquanto a dextrina levou ao aumento do grau de dispers?o, na faixa alcalina. O tanino, reagente org?nico natural, que n?o agride o meio ambiente em caso de descarte, apresentou um aumento no grau de dispers?o da hematita, mesmo em concentra??es mais baixas (150 g/t). O ?cido c?trico tamb?m levou ao aumento do grau de dispers?o da hematita. A raz?o SiO2 /Na2O ? um fator que pode interferir na a??o do silicato de s?dio na flota??o do min?rio de ferro. O silicato de s?dio C112, com raz?o mais baixa, n?o alterou significativamente o grau de dispers?o; o silicato de s?dio R3342, com maior raz?o, foi o que levou ao maior grau de dispers?o. J? o silicato de s?dio R2252 apresentou um aumento do grau de dispers?o por volta de pH 8,5. O Dismulgan V3377 n?o mostrou muita diferen?a no grau de dispers?o em todas as dosagens, mostrando certa semelhan?a com a curva de hematita pura. O Dispersogen LFS e o Polymax T10 levaram ao aumento do grau de dispers?o na faixa alcalina de pH. O Bozefloc AE 738 pode ser sugerido como floculante. Em pH 10,5 apresentou uma boa agrega??o nas dosagens de 500g/t e 1000g/t. O reagente Dispersol 589 apresentou, em todas as dosagens estudadas, um aumento altamente significativo do grau de dispers?o em toda faixa de pH. Em pH = 10,5, o reagente Depramin 158 levou a um aumento significativo do grau de dispers?o. Na faixa ?cida de pH, esse reagente levou a um grau de dispers?o de aproximadamente 50%.The iron content in ores that will be mined is steadily decreasing. The lower grade ores require finer grinding. Metallic oxides and hydroxides such as iron oxides acquire electrical when dispersed in aqueous medium. The changes on the oxides surfaces and the formation of the electrically charged interface are controlled by the pH and the ionic force of the solution in which they are dispersed. The factors lead to the need of investigating the effect of dispersion on flotation, thickening, and filtration stages. This laboratory scale study aimed at contributing to a better understanding of iron ores processing addressing the dispersion of hematite pulps in the presence of dispersing or aggregating reagents. Fourteen organic and inorganic reagents were evaluated in dispersion experiments. The study of hematite dispersion in the absence of reagents showed a decrease in the dispersion degree in the pH range between 6.5 and 7.5. The additions of starch and ground corn (fub?) caused aggregation of hematite in the full pH range, while dextrin increased the dispersion degree in the alkaline range. Tannin, a natural organic reagent, not aggressive to the environment in case of disposal, increased the hematite dispersion degree even at low concentrations (150 g/t). Citric acid also increased the hematite dispersion degree. The SiO2 /Na2O ratio is a factor that may interfere in the action of sodium silicate in iron ore flotation. The sodium silicate - C112, presenting the lowest ratio, did not change significantly the dispersion degree; sodium silicate R3342, presenting the highest ratio, led to the highest dispersion degree. Sodium silicate R2252 caused an increase in the dispersion degree around pH 8.5. Dismulgan V3377 did not affect significantly the dispersion degree leading to results similar to those achieved in the absence of reagents. Dispersogen LFS and Polymax T10 increased the dispersion degree in the alkaline pH range. Bozefloc AE 738 may be suggested as flocculant, enhancing the aggregation at pH 10.5 at dosages of 500g/t and 1000g/t. Dispersol 589 caused, a significant increase in the dispersion degree in the full pH range. At pH = 10.5, Depramin 158 led enhanced significantly the dispersion degree. In the acidic pH range the dispersion degree reached approximately 50%

Kaolinite removal from bauxite by flotation.

This paper presents a potential condition to separate kaolinite through flotation when it is present in bauxite ore. This research anticipates a Brazilian industry requirement, considering the tendency towards the need for aluminosilicates removal from bauxite ores, as has already occurred in China. Kaolinite is the most abundant aluminosilicate, and gibbsite is the main aluminum bearing mineral in Brazilian bauxite ores. The first step was a fundamental study involving microflotation experiments with pure samples of kaolinite and gibbsite. Ammonium quaternary salts and amines were used as the collector and corn starch as the depressant. In a fundamental study, the best conditions determined in the first step were evaluated for the flotation of kaolinite from bauxite ore using laboratory scale experiments. Tests with AQ142/starch (pH 10) and CTAB (pH 7) led to satisfactory results. In general, the highest values of alumina/silica mass ratio were obtained with AQ142/starch and the highest values of mass recovery and metallurgical recovery were achieved with CTAB

Kaolinite microflotation and zeta potential measurements in the presence of ammonium quaternary salts.

Studies on kaolinite flotation are being driven by Chinese bauxite characteristics, presenting low alumina:silica weight ratios. This paper addresses the effect of the presence of cetyl pyridine chloride (CPC) and cetyl trimethyl ammonium bromide (CTAB) on kaolinite floatability and zeta potential. The reagents were dosed at three concentrations and the best floatability results were achieved at the highest concentration level (1x10-4 mol/L). Zeta potential determinations showed that both quaternary salts (CPC and CTAB) shift the kaolinite zeta potential to more positive values the specific collectors adsorption onto the mineral surface