Afonso Henriques Martins

Indium adsorption onto ion exchange polymeric resins

Experimental results for indium adsorption onto some ion exchange resins of different organic functional groups are presented. The following resins were tested: Ionac® SR-5 and Ionac® SR-12 (Sybron Chemicals), S950 (Purolite Company) and Amberlite® IR-120P (Rohm&Haas, Brazil). The indium concentration in the aqueous solution was based on a typical indium sulfate leach liquor obtained from a zinc hydrometallurgical processing route of a Brazilian plant and treated with solvent extraction for some impurities removal. The performance of the resin was based on the indium adsorption loading capacity and its selectivity concerning iron as a typical impurity present in the solution. Some parameters, such as initial pH and volume of the aqueous feed solution and contact time were studied. Batch tests were carried out. The experimental results allowed to select the chelating resin containing iminodiacetic acid groups with high potential for purification of the indium sulfate solution.

Recovery of tin and copper by recycling of printed circuit boards from obsolete computers

This paper presents the experimental results for the leaching of printed circuit boards (PCB) from obsolete computers for extracting and recovering tin and copper by means of leaching followed by precipitation. Printed circuit boards were dismantled, cut into small pieces, and fed into a cylinder mill. The powder obtained was leached by using the aqueous solutions 2.18N H2SO4, 2.18N H2SO4 + 3.0N HCl, 3.0N HCl, and 3.0N HCl + 1.0N HNO3. The lowest values for the percentage of metal extraction were obtained with 2.18N H2SO4 (2.7% for Sn and lower than 0.01% for Cu), while the 3.0N HCl + 1.0N HNO3 leach system exhibited an extraction of 98% for Sn and 93% for Cu. Precipitates were obtained at different pH values by neutralizing the leach liquors using NaOH. The 3.0N HCl + 1.0N HNO3 leach system presented the highest recovery values from the powder feed (84.1% for Sn and 31.9% for Cu), as well as from the leach liquor (85.8% for Sn and 34.3% for Cu).

Selective separation of indium by iminodiacetic acid chelating resin

Indium can be recovered by treating residues, flue dusts, slags, and metallic intermediates in zinc smelting. This paper investigates the adsorption characteristics of indium and iron on an iminodiacetic acid chelating resin, Amberlite®IRC748 (Rohm and Haas Co.-USA). High concentrations of iron are always present in the aqueous feed solution of indium recovery. In addition, the chemical behaviour of iron in adsorptive systems is similar to that of indium. The metal concentrations in the aqueous solution were based on typical indium sulfate leach liquor obtained from zinc hydrometallurgical processing in a Brazilian plant. The ionic adsorption experiments were carried out by the continuous column method. Amberlite®IRC748 resin had a high affinity for indium under acidic conditions. Indium ions adsorbed onto the polymeric resin were eluted with a 0.5mol/dm3 sulphuric acid solution passed through the resin bed in the column. 99.5% pure indium sulfate aqueous solution was obtained using the iminodiacetic acid chelating resin Amberlite®IRC748.

Cyanide regeneration by AVR process using ion exchange polymeric resins

Abstract This work presents laboratory bench scale results for cyanide regeneration from pure alkaline aqueous solutions of gold, copper and iron cyanocomplexes using an innovative option of the AVR process associated to the ion exchange polymeric resins Imac HP555s ® ((Room&Haas––USA) and Amberlite IRA-420 ® (Room&Haas Brasil Ltda.) in columns. The resin Imac HP555s ® adsorbed 64.5% CN from the alkaline solution containing metal cyanocomplexes. Meanwhile, the elution stage with H 2 SO 4 and thiourea reached 31.2% CN, 86.2% Au, 86.4% Cu and 41.5% Fe. The resin IRA-420 ® adsorbed 53.4% CN under the same experimental conditions adopted for the resin Imac HP555s ® . The resin Amberlite IRA-420 ® eluted 48% CN, 96.8% Au, 9.1% Cu and 76% Fe.

Sulfuric activation of a Brazilian manganese ore for heavy metals removal

Abstract Manganese oxide which is used in the production of primary batteries usually has some heavy metals associated with its mineral sources. One of the hydrometallurgical procedures to remove these impurities is sulfuric activation. This consists of a controlled sulfuric acid leach aimed at the solubilization of some heavy metals and minimum manganese extraction. The goal of this work is to evaluate some sulfuric activation parameters in the treatment of the Mina do Azul (Brazil) manganese ore for maximum heavy metals removal. Laboratory bench-scale experiments were carried out to study the more important variables, viz.: activation time, solid–liquid ratio, sulfuric acid concentration in the activation solution and stirring intensity. The evaluation of the variables and their interactions on the manganese and heavy metals extraction was made by statistical experimental design using the complete factorial method for four variables at two experimental levels. The sulfuric acid concentration showed the greatest influence on the experimental responses for manganese, nickel and cobalt extraction. The solid–liquid ratio was the most significant variable as regards iron and copper extraction. The optimization was accomplished by the use of the ascendent step statistical methodology and it allowed the determination of the best experimental conditions for maximum heavy metals extraction by sulfuric activation of the manganese ore under study. The experimental results obtained under the optimum conditions were 15.0% for manganese extraction while the maximum nickel, iron and copper extractions were 74.4%, 37.4% and 41.2%, respectively.

Reciclagem de sucata de jóias para a recuperação hidrometalúrgica de ouro e prata

A great amount of scrap metal waste is lost in the manufacturing of gold jewelry due the lack of available knowledge for precious metal recovery in small jewelery shops. This study presents the experimental results on a bench laboratory scale of a hydrometallurgical route to treat gold jewelry scrap using samples with proportions that are higher and lower than 10% Ag. The adopted route consisted of preliminary sampling, leaching with HNO 3 to extract the silver, followed by aqua regia leaching of a gold solid residue from the previous leaching stage to dissolve the contained gold. Some typical parameters of the leaching stage were evaluated with the use of a statistical planning of experiments by “The complete Factorial Method” with two experimental levels. The optimum experimental conditions for the maximum metallic extraction were determined by “the ascending path method for statistical optimization”. The leaching liquors were treated,

Extração por solventes aplicada à remoção de metais pesados presentes no licor de lixiviação do minério de manganês da Mina do Azul (PA)

The goal of this experimental work was to treat a manganese sulfate aqueous solution obtained from the sulfuric acid leaching of Mina do Azul manganese ore (Brazil) to remove copper, nickel, cobalt and iron by solvent extraction using CYANEX302O solubilized in Exxsol D-100O. The experimental results for the individualized extraction stage were considered satisfactory and reached 98% Zn, 92% Ni and 77% Fe, while more than 90% of manganese was kept in solution. The experimental conditions for maximum impurities extraction and minimum manganese extraction were 6.0% v/v CYANEX302O in the organic phase, 3 minutes of contact time between phases and an organic/aqueous phase ratio equal to 5.5. Under these conditions, the results were 3.7% extraction of manganese, 77.1% iron, 89.7% zinc and 31.3% extraction of nickel.

Extração por solventes aplicada à recuperação de cianetos

This technical note presents the preliminary experimental results at laboratory bench scale-up for the study involving the usage of commercial organic extractant CYANEX 921® (trioctylfosfine oxide) diluted in xylene for cyanide extraction from pure alkaline aqueous solution with a chemical composition similar to a typical cyanidation liquor of a gold ore. The experimental results for only one contact stage showed that an increase of the CYANEX 921® concentration in the organic phase improved the percent of cyanide extraction. Besides, the zinc presence in the feed aqueous phase as complexing agent for cyanide also improved the cyanide extraction (38.48%) as compared to the result for the experiment without zinc (35.50%). The highest values for percent of cyanide extraction were obtained at the initial pH of the aqueous phase equals to 9.0.

Evaluation of internal corrosion in a Brazilian iron ore slurry pipeline based on the characterization of scales and tubercles

The transport capacity of long-distance slurry pumping systems is directly related to the roughness of the pipe. In this context, corrosion plays an important role, especially when dealing with old pipes. Chemical, mineralogical and microstructural analyses were performed on materials removed from the internal surface of an iron ore slurry pipeline in order to access their composition and to check if they were a result of internal pipeline corrosion. This pipeline has been operating since 1977. It was found that the tubercles formed on the internal wall of the pipe presented botryoidal magnetite as their essential composition. As the amount of magnetite is very low in the transported slurry and magnetite with botryoidal morphology is not present in the processed iron ore, it was concluded that this magnetite is a result of a corrosion process occurring on the internal wall of the pipeline.

Metal Bioavailability Potential of São Francisco River Sediments in Três Marias (Minas Gerais – Brazil)

Sediment contamination by metals is very common and frequently researched worldwide with the objective of assessing the environmental impact of these contaminants. The bulk metal concentration in sediments is not enough for assessing toxicity and therefore, needs additional research and assays. To estimate the potentially bioavailable fraction of the metals in the sediment, the acid-volatile sulfides / simultane ously extracted metals (AVS/SEM) method was used. Seven samples in duplicate were collected from the Sao Francisco River and its tributary, near a zinc metallurgical plant in the city of Tres Marias (MG). The AVS/SEM results suggest that, although the bulk metal concentrations are above TEL (Threshold Effects Level: A chemical concentration above which some adverse effect to biota is expected), samples from the Sao Francisco River presented relatively low potential for bioavailability (uncertain toxicity). These results should be taken into consideration before deciding about contaminated sediment management. Keyword: AVS-SEM, bioavailability, metals, Sao Francisco River