Antônio Eduardo Clark Peres

Adsorption of oleate and octyl-hydroxamate on to rare-earths minerals☆

The adsorption of sodium oleate and potassium octyl-hydroxamate onto the rare-earths minerals monazite and bastnaesite was investigated through microflotation experiments, zeta potential determinations and infrared spectroscopy. The monazite and bastnaesite samples were purified in the laboratory reaching, respectively, final grades of 68.7 and 45.3 % RE2O3 + ThO2. The results confirm that sodium oleate chemisorbs onto bastnaesite and suggest a physical adsorption mechanism of this reagent onto monazite. Despite the lack of a full confirmation from FTIR spectrometry, there is a possibility of oleate chemisorption onto monazite in the pH range above the isoelectric point. A chemical adsorption mechanism was established for the interaction between octylhydroxamate and both minerals.

Depression of iron oxides with corn starches

Abstract A review of the industrial utilisation of corn starches in flotation, in Brazil, is presented with emphasis on iron oxides depression in the reverse cationic flotation of itabiritic ores. The current overall consuption reaches 40,000 metric tons per yeaer, iron ores concentration representing approximately 80% of the total amount. The industrial replacement of very pure conventional starch (assaying over 98% amylose + amylopectin on a dry basis) by coarser non conventional starches (containing around 7% proteins + between 1% and 3% oil, beyond amylose + amylopectin) is discussed. Some relevant aspects of different starch types are reported, highlighting an analysis of the action of the major individual components. The experimental results from microflotation tests in a modified Hallimond tube showed that zein, the most abundant corn protein, is a hematite depressant as efficient as amylopectin and conventional corn starch. The poorest depression performance came from a non conventional starch with a high oil content.

Utilisation of hydroxamates in minerals froth flotation

Abstract Following a critical review of the utilisation of chelating reagents (hydroxamates) in minerals flotation, results of a series of experiments performed in the presence of an experimental commercial hydroxamate as collector, at bench scale with two different ores and in a microflotation cell with several combinations of minerals (most of them “sparingly soluble minerals”) are presented. The conclusion is that the selectivity of minerals flotation with hydroxamates depends on a balance between the solubility of the mineral and the stability of the complex formed with the cation of the lattice. A favourable condition for the selective utilisation of hydroxamates as collectors is visualised if the mineral to be floated is the most soluble in the system and the chelate formed between the cation in the lattice and hydroxamate is the most stable.

Effect of sodium metasilicate and sodium sulphide on the floatability of monazite-zircon-rutile with oleate and hydroxamates

The floatability characteristics of monazite, zircon and rutile were investigated in a modified Hallimond tube. Sodium metasilicate and sodium sulphide were employed as depressants and sodium oleate, a commercial hydroxamate and a pure hydroxamate were utilized as collectors. Sodium metasilicate is more effective than sodium sulphide as a depressant for zircon and rutile. The best selectivity condition (depression of zircon and rutile and little effect on monazite) is achieved with either oleate or commericial hydroxamate as collector, at pH = 10. The effect of the conditioning temperature was also studied, revealing that, in some instances, a higher temperature enhances the selectivity, but in other cases the floatability of zircon and rutile is more strongly improved than that of monazite.

The effect of starch, amylose and amylopectin on the depression of oxi-minerals

Abstract In the present study microflotation tests were performed on pure mineral systems involving calcite, apatite, quartz and hematite. For the two first minerals sodium oleate was employed as collector and for the two latter the collector chosen was dodecylamine hydrochloride. Purified potato starch amylose and amylopectin (supplied by B.D.H.) and tapioca starch (commercial grade, from Thailand) were used as depressants in all systems. With the exception of hematite, all other minerals were depressed by the polysaccharides in the following decreasing depression order: tapioca starch (made up of approximately 17% amylose and 83% amylopectin), amylopectin and amylose. For hematite, amylopectin showed stronger depression than tapioca starch and amylose. Another important finding refers to the great differences observed for the ratios of collector to depressant concentrations, which were shown to vary from 1 to 11 for quartz to 3 to 1 for calcite (for a constant depressant concentration of 10 mg/l).

The role of sodium sulphide in amine flotation of silicate zinc minerals

Abstract The role of sodium sulphide in amine flotation of the silicate zinc minerals willemite and hemimorphite is discussed. Data from the literature are compared with experimental results obtained by the authors in Hallimond tube floatability tests. The activating effect of sodium sulphide was investigated considering the dual role of this reagent, either as in pre-sulphidization or as flotation pH regulator. The practical conclusion of these fundamental studies is the possibility of partial replacement of sodium sulphide by sodium hydroxide, in amine flotation systems of zinc silicates, with significant benefits in terms of reagnet costs and environmental impact.

Electrokinetic properties of wavellite and its floatability with cationic and anionic collectors

The reverse apatite flotation with fatty acids has been widely used for the reduction of phosphorus content of magmatic origin iron ores. However, the occurrence of phosphorus intensely disseminated as secondary minerals such as wavellite renders the anionic reverse flotation a challenge. Zeta potential measurements and microflotation tests of wavellite with the use of anionic and cationic collectors were carried out in this work. The wavellites IEP value was achieved at pH 4.5. Below the IEP value, the surface positively charged sites are made up of aluminum ions. The species H(+), Al(OH)(2)(+), Al(OH)(2+), Al(3+), OH(-), H(2)PO(4)(-), HPO(4)(2-), and PO(4)(3-) play a role in the protonation and deprotonation reactions that will determine the wavellite-solution interface properties. The highest values of wavellites floatability under basic pH conditions were achieved in the presence of cationic collectors (1 × 10(-4) mol L(-1)). The formation of surface complexes and the precipitation of insoluble salt of aluminum onto wavellite surface seems to be the most likely hypothesis for the chemical nature interactions between amines and wavellite. The surface formation of aluminum oleate on the wavellites surface seems to be the most probable hypothesis for the adsorption mechanism and the resultant high floatability of wavellite between pH 7.5 and pH 10.0 in the presence of sodium oleate (1 × 10(-4) mol L(-1)). The results showed that the cationic reverse flotation of secondary phosphates is a promising route to reduce the phosphorus content of iron ores from deposits that underwent a supergene enrichment process, since wavellite floatability in the alkaline pH range, using amine as collector, was not significantly affected by the presence of corn starch.

Dynamic model of a flotation column

A linear multivariable model for a flotation column is derived from process analysis and experimental data. The data have been taken from a pilot-scale column (height 720 cm; diameter 5.1 cm) with all necessary instrumentation installed. The flotation column was operated in a water-air system. The model has been derived aimed at utilisation in the design of the control system. The model describes the relationship between controlled variables (froth layer height, bias and air holdup in the recovery zone) and manipulated variables (wash water, air and non-floated fraction flowrates). It has been validated comparing the experimental data with those obtained from simulations. Finally, the conditions under which the model is applicable are presented.

Technical note bench scale flotation of a brazilian monazite ore

Abstract Preliminary studies of the floatability characteristics of monazite, zircon and rutile, performed in a modified Hallimond tube, initiated a bench scale investigation of the flotation of a Brazilian monazite ore from Sao Goncalo do Sapucai, MG. The testwork was conducted with the utilisation of a commercial hydroxamate and sodium oleate as collectors and sodium metasilicate as depressant. In all tests, the best collector/depressant ratio defined during the microflotation experiments was confirmed at bench scale. The results indicated that with both collectors it is possible to produce a high purity cleaner monazite concentrate (> 60% RE 2 O 3 ). The concentrations of collector and depressant must be well defined to prevent a significant increase in the flotation of gamgue minerals such as ilmenite, zircon and rutile, causing contamination of the monazite concentrate.

Reverse magnesite flotation

Abstract The present investigation deals with the production, at bench scale, of a high purity magnesite concentrate by means of reverse cationic flotation as an alternative to the direct anionic flotation currently employed in a concentrator in Brazil. The specification of the presently produced concentrate, in terms of maximum SiO 2 content, is 0.30% (calcined basis) and the weight recovery of the circuit is approximately 84%. The aim of this study was to produce concentrates with SiO 2 content ≤ 0.20% (calcined basis) and weight recovery ≥ 84%. A two level factorial design was employed in the first stage to optimise the variables that affect the behaviour of the system. In the second stage, the best conditions defined in the first stage were utilised in a locked cycle test, with simulation of circulating load, to predict the stability of the circuit in a continuous process. The main variables investigated were: percent solids and pH of the pulp, collector (ether amine) dosage, depressant (corn starch) dosage and flotation residence time. The aim of the study was achieved and a concentrate with 0.17% SiO 2 , at a weight recovery level of 92.17%, was produced in the tests with simulation of circulating load in a rougher - cleaner - recleaner circuit. Lower SiO 2 contents could be reached with a reduction in weight recovery.