A amina, quando adicionada em solução aquosa contendo quartzo, adsorve--se na interface sólido--líquido em determinado pH, tornando as partículas de quartzo hidrofóbicas. Tal hidrofobicidade pode ser afetada pela adição de amido, que é capaz de adsorver--se mutuamente com a amina, possivelmente devido à formação de um complexo helicoidal entre os reagentes, denominado de clatrato. Assim, o quartzo readquire caráter hidrofílico, por a amina ser mascarada pelo invólucro de amido. Foram realizados ensaios de microflotação e eletroforese. Nos ensaios de microflotação, foi estudada a flotabilidade da hematita e quartzo com os reagentes eteramina e os amidos maisena e amidex 4001. A maisena promoveu diminuição da flotabilidade do quartzo de 95% para 35% com aumento da dosagem de amina. O amidex não mostrou essa tendência nas condições estudadas. A depressão do quartzo foi favorecida pelo aumento nas dosagens tanto de maisena quanto de amina, e por condições básicas de pH. Os ensaios de eletroforese, para determinação do potencial zeta, foram realizados com amina e amina e maisena em concentrações de 80 mg/L, nas quais houve evidência da formação de clatratos. O potencial zeta apresentou valores menos negativos em pH superior a 7, quando comparado com o potencial zeta de quartzo condicionado apenas com amina. Por fim realizou--se ensaios com amina e amidex em concentrações de 80 mg/L, nas quais não foi observada variação significativa do potencial zeta quando comparado com potencial zeta de quartzo com amina nas mesmas condições. PALAVRAS--CHAVE: flotação, minério de ferro, clatratos. SELECTIVITY IN THE REVERSE CATIONIC FLOTATION OF IRON ORE ABSTRACTAmines adsorbs at the solid--liquid interface when added to aqueous solution which contains quartz particles, under certain pH conditions, rendering these particles hydrophobic. However, this hydrophobicity may be affected by the addition of starch into the system, which is capable of adsorbing mutually with amine due to the formation of a helical complex between the reagents, called clathrate. Therefore, the quartz particles reacquire a hydrophilic surface since the amine is hidden by the starch envelopment. Microflotation and electrophoresis experiments were conducted with hematite and quartz and the reagents etheramine (frother and quartz collector) and corn starch and amidex 4001 (hematite depressants). The corn starch promoted a decrease in the floatability of quartz, dropping from 95% to 35% as amine dosage was increased. amidex did not show this trend at any condition investigated. Quartz depression was favored by the increase in the dosage of both amine and corn starch and by alcaline pH conditions. The electrophoreses experiments for zeta potential measurements were conducted with amine and amine and corn starch at 80 mg/L, there was evidences of the formation of clathrates were observed. In these conditions, higher zeta potential values were obtained when compared with the results obtained for quartz with amine only.
Tailings disposal in the form of diluted slurries has a tendency for particle size segregation, where coarse particles settle near the discharge point, and finer particles are carried by the water flux to more distant regions. This causes a loss of reservoir capacity due to voids between the coarser particles and increased water content in the deposit. This work aimed to evaluate the feasibility of reaching non-segregable high-density slurries with fine tailings from the niobium oreflotation process and measure its disposal parameters. The innovation is to achieve increased solids percentage in the settled deposit and to avoid particle size segregation along the slurry path with niobium tailings. The study involved physical, chemical, and mineralogical characterization and semi-pilot thickening tests to produce enough volume of underflow with different bed heights and solids flux rates. Slump, rheology, and flume tests were performed to evaluate underflow disposal characteristics. The results indicated that the thickener bed height did not significantly influence the underflow solids content, yield stress, or slump. The solids flux rate, on the other side, had a greater influence—the higher it was, the lower the solids content, yield stress, and disposal angle, along with a higher slump. In flume tests, a high density of non-segregable tailings slurry was achieved with 1.96 t/m3, corresponding to an underflow with 66.8% solids, 43.9 Pa of yield stress with 0.5 (t/h)/m2, and 0.5 m of bed height.
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