BRPI0705593B1 - method of quantifying amines in iron ore flotation waste - Google Patents

Abstract

amine quantification method in iron ore flotation residues. The present invention relates to a method of quantifying fatty amines from effluents generated by the iron ore reverse flotation process using a colorimetric technique containing bromocresol green as an organic dye.

Description

"METHOD OF QUANTIFICATION OF AMINES IN IRON ORE FLOTATION WASTE" The present invention relates to a method of quantifying fatty amines from effluents generated by the reverse flotation process of iron ore using a colorimetric technique containing iron ore green. bromocresol as an organic dye.

Due to the increasing demand for iron, deposits of high grade iron ores have been decreasing and there is a need to exploit deposits with lower grades.

Deposits with high iron content are only submitted to comminution and grading steps. While in deposits with low iron content, concentration steps are required to achieve market specifications such as minimum iron content and minimization of undesirable substances such as silica. The main concentration method used for the treatment of iron ore is reverse cationic flotation. This method aims to promote the separation between iron oxides and silica.

The main reagents used in cationic flotation are starch, which has the function of depressing iron minerals preventing them from being floated, and fatty amines, which have the function of collector of quartz minerals [Samarco Mineração, www.samarco.com1 [Quast, KB 2000. A Review of Hematite Flotation Using 12-Carbon Chain Collectors. Minerals Engineering, 13: 1361-1376] [Scoott, J.L .; Smith, R.W. 1991. Diamine Flotation of Quartz. Minerals Engineering, 4: 141-150] [Fuerstenau, M.C. 1985. Chemistry of Flotation. New York, Society of Mining Engineers].

After flotation, most of the fatty amines used are trapped in flotation material (predominantly quartz), which is deposited in tailings dams. The possibility of reuse of the amines would result in considerable reduction of operating costs, as well as a reduction in the amount of reagents released to the environment. It is estimated that approximately 5500 tons of amine derivatives are used annually in Brazil [Neder, E.E. 2005. The Use of Fatty Amines and their Derivatives in the Flotation of Brazilian Ore. University of Sao Paulo. Master's Dissertation, 91 p] The expectation for the next years is that the consumption of amines should increase due to the growing world demand for iron ore. Amines are relatively expensive but important reagents in the concentration process, accounting for about 48% of total reagents costs in the flotation process [Batisteli, G.M.B. 2007. Residual Amine in Reverse Cationic Flotation of Iron Ore Federal University of Minas Gerais, Master's Dissertation, 118 p] and 30% of the operating costs of global beneficiation processing [Neder, 2005], In view of this, it is of great interest. the reduction in the cost of amines in the iron ore processing process. To this end, one of the alternatives involves the reuse of amines in reverse ore flotation. DE10065846-A1 describes the only reuse process of amines in the iron ore flotation process disclosed so far. In the amine reuse process of the above document, after a first flotation, the obtained flotate water is reused for the utilization of part of the amine in subsequent flotations. As float water is reused, smaller and smaller amounts of amine remain in it, which requires, with each new reuse of float water, the inclusion of increasing amounts of amine to continue to achieve maximum use in the float. beneficiation process.

Although the above cited patent application describes this process, the lack of a method of quantifying amine in float water makes it impossible to know the exact and correct amount of amine remaining in float water and therefore the dose to be added.

Therefore, in addition to efforts to develop amine reuse processes in the ore beneficiation process, it is essential to have a method of quantifying amines in the float in order to assess whether amines are actually being reused and, if so, how much amine is reused.

In the 1940s and 1950s, various methods of quantifying quaternary ammonium salts based on colorimetry were developed, involving the use of organic dyes of various types such as bromophenol blue, bromotimol blue, bromocresol green, among others [Mukerjee, P , 1956. Use of lonic Dyes in the Analylis of lonic Surfactants and Other lonic Organic Compounds. Analytical Chemistry, Vol. 28, no. 5, pp. 870-873] [Colichman, E.L. 1950. Conductance of Long Chain Quaternary Salts in Bromophenolate Blue Solutions. Journal Am. Chem. Soc., Vol. 72, pp. 1834-1835] [Colichman, E.L. 1947. Photocolorimetric Method for Determination of Quaternary Ammonium Salts. Analytical Chemistry, 19, p. 430] [Auerbach, M E. 1944. Colorimetric Assay of Quaternary Ammonium salts. Ind. Eng. Chem., Analytical edition, 16, pp. 739] [Auerbach, M.E. 1943. Germicidal Quaternary Ammonium salts in Dilute Solution. Ind. Eng. Chem., Analytical edition, 15, pp. 492-493] [Ralston, A.W .; Hoffman, E.J .; Hoerr, C.W .; Selby, W.M. 1941. Studies on Hight Molecular Weight Aliphatic Amines and their Salts. Behavior of the Hydrochlorides of Dodecylamine and Octadecylamine in Water. Journal Am. Chem. Soc., Vol. 63, pp. 1598-1601] There is currently some work on quantification of fatty amines using the ninhhydrin methodology [Reis, O. B. 2004. Preliminary study on the reuse of amines used in iron ore flotation. Federal University of Ouro Preto. Masters dissertation. 56p] [Theodore, A.L. and Leo, V.A. 2004. Recovery of Amines Used in Iron Ore Flotation Using Natural Zeolites. Minas School Magazine, Ouro Preto, 57 (3); 197-201] [Stapelfeldt, F .; Carvalho, C. F .; Chaves, L.C .; Reis, O. B. 2002. Quantification, decomposition and reuse of amines in reverse ore flotation residues. XIX ENTMME, National Meeting of Ore Treatment, Recife] [Chaves, L. C. 2001. Study of Solid Waste Generated in Iron Ore Flotation: Quantification and Decomposition of Amines in the Environment.

Federal University of Ouro Preto. Master's thesis, 89p] Colorimetric methods consist of the formation of colored salts between the amine and the organic dye that are extracted with organic solvents.

The mentioned organic dyes are soluble in aqueous solution and insoluble in organic solvents and, upon reaction with the amine salts, the formed compound becomes soluble in organic solvents.

Through colorimetry the intensity of the color formed is measured. For each amine compound to be determined, a calibration curve with sample standards of known concentration is made. This curve is used to determine the concentration of amines in samples of unknown concentration. Ninhidrin is a colorimetric method that was initially used for quantification of α amino acids (Greenstein, JP; Winitz, M. 1961. Chemistry of the amino acids. Ed. John Wiley & Sons, New York, vol. 2, chap. 11] It was observed that by adding α amino acid in a medium containing trichetohydrindylidene (ninhhydrin) a violet coloration was produced which was attributed to the formation of dichetohydrindylidene dihydride hydrindamine. concentration of the compounds in solution, with the violet coloration producing a maximum absorption in the regions of 550 - 570nm.

Although primarily used for the qualitative and quantitative determination of α amino acids, ninhhydrin also reacts with peptides, primary and secondary amines, ammonia or amino alcohol and therefore cannot be considered a specific method. When used for quantitative determinations, the total removal of interfering substances is extremely important. The reaction of ninhhydrin is most effective at higher temperatures. Between 60 ° C and 100 ° C, formation of the dihydride dihydridyl dihydride hydramine occurs [Lehninger, A.L .; Nelson, D.L .; Cox, M.M. 1993. Principles of Biochemistry, New York, Worth Publishers, 124p], Previous studies have shown that this method has good sensitivity (detection up to 1ml_1) and repeatability for natural samples. However, the problem with its use lies in the low yield of amine extraction, especially in solids [Reis, 2004] [Chaves, 2001]. Iron ore flotation generates two products, the concentrate containing iron ore and the tailings that are deposited in dams, ie. a liquid fraction and a solid fraction. Of the total amma added, the loss of amines occurs in the solid fraction of the tailings. The effluents and waste generated basically contain silica, organic compounds consisting of aliphatic amines (primary, secondary and tertiary), as well as significant concentrations of iron ore and other metals. Normally flotation tailings are routed from the plant to the dams where solid particles are expected to be trapped.

In the state of the art, very few patents have been found for amine quantification methodologies using colorimetric methods. Caillouette, James C. in US5998161: "Amine detection by color change in human body moisture" has developed a method for detecting amines associated with pathogenic bacteria using bromocresol green as an organic dye for amines. Already Beauchamp, Jesse L In US20060263257A1: "Optical gas sensor based on dyed high surface area substrates", developed a new optical sensor that uses bromocresol green as an organic dye. This sensor is capable of identifying aliphatic amines such as tert-butylamine, diethylamine and triethylamine. and also pyridine and aniline.

However, to date no amine quantification methodology has been found using ninhhydrin's different organic dye for the purpose of dosing fatty amines from effluents from the iron ore reverse flotation process and proving to be efficient. The present invention provides a method of quantifying the fatty amines in the iron ore reverse flotation process using bromocresol green as a dye, especially aiming at maximizing the reuse of the amines, as it allows to identify the exact amount recovered in the process. the exact amount to be added in the next process.

It is known that amines in the presence of bromocresol green can form two types of compounds: in alkaline solutions a green colored diamine salt is formed, while in acidic solutions a yellow colored monoamine salt is formed [Mukerjee. 1956: Auerbach, 1943], In the present method of quantification of amines, the reaction between eteramine and bromocresol green occurs at pH = 5, therefore a monoamine salt is formed. The present method allows quantification of the amines called etheramine Flotigam EDA 3B and eterdiamine Flotigam 2835, produced by Clariant Company, which are used in flotation processes in various mining companies.

According to Clariant Company Newsletter [Company Clariant S.A. 1999. Product Newsletter. Sao Paulo. 5p], the ethersines studied have the following chemical compositions: [RO- (CH2) 3-NH3] + CH3COO '(Flotigam EDA 3B) where, R = alkyl radical of 10 to 14 carbon atoms and [R-0- ( CH 2) 3-NH- (CH 2) 3 -NH 3 r CH 3 COO (Flotigam 2835) where, R = alkyl radical of 10 or more carbon atoms. The invention may be better understood through the examples below.

Example 1: Quantification of fatty amines Using EDA 3B etheramine and a mixture of 25% EDA etheramine 3B and 75% F2835 used in the reverse flotation process of the iron ore, calibration curves were made for EDA 3B. and for the mixture EDA 3B and F2835.

Thus, the colorimetric methodology was applied using bromocresol green dye. The samples are placed in a settling funnel together with the bromocresol green dye, buffer at pH = 5, and chloroform, forming a colored and soluble chloroform compound. Absorbance measurements can be made on a Merck-SQ118 spectrophotometer at 409nm. Whites can be made with distilled water instead of amine solutions.

The parameters used to validate the method are the usual ones, such as accuracy, precision, linearity and limit of detection. The linearity of the method is determined by performing the analytical curve. Amine standards are 5, 10, 20. 30, 40 and 50 mg / L. Linearity can be estimated by linear regression analysis using the least squares method.

To determine accuracy, the standard 36mg / L EDA 3B sample is prepared and analyzed in triplicate and on five different days. Accuracy can be assessed by the recovery test, in triplicate, an effluent sample from starch flotation and possible interferents from iron ore. Three known concentration standards were used from EDA 3B: 10, 25 and 50 mg / L.

Example 2: Determination of amines in effluents For testing of amine determination in effluents and reverse flotation residues of iron ore, benchtop flotations were performed using procedures described by Stapelfeldt et al in XIX ENTMME -Recife, Pernambuco [2002]. The procedures were performed in a Denver benchtop flotation cell with a 2 liter vat, using, for example, 1150 g of iron ore together with 1400 mL of water. The flotation process conditions were: 1200 rpm, starch conditioning for 5 minutes and collector conditioning for 1 minute and foam removal. The processes were performed at pH = 10.5 and amine dosage of 40g / t (gram of amine per ton of ore). After bench flotation, as in the normal flotation of iron ore, solid and liquid fractions were obtained, and all fractions were analyzed by the proposed bromocresol green method and also by the traditionally used ninhhydrin method.

For solid samples, before amine quantification, amine extraction was performed by placing 10 g of the residue (obtained from flotation tests) in contact with 100 mL of millü-Q water under agitation. The suspension was filtered, and the filtrate was analyzed for the amount of desorbed amine according to the procedures described for bromocresol green and ninhhydrin. Table 1 shows the data from the analytical curves for EDA 3B and the EDA 3B / F 2835 mixture. The analytical curve was linear from 5.0-50 mg / L in both cases.

Table 1. Linear regression analysis of the analytical curve for EDA 3B and EDA 3B / F 2835 mixture The results of the precision assessment are shown in Table 2. The coefficient of variation obtained for bromocresol green shows that the method has precision. satisfactory. In the tests performed with the traditional ninhhydrin method, the coefficient of variation was quite high, showing that the method is not as accurate as bromocresol green for the quantification of amines in the reverse flotation effluents of iron ore.

Table 2. Accuracy assessment for bromocresol green (BROMOCRESOL GREEN) and ninhhydrin (NINHYDRINE).

Table 3 shows the results obtained for the accuracy of the bromocresol green method. The recovery values were considered acceptable for the proposed method. It can be said that the method presents good selectivity for quantifying amine grease in the matrix used. To confirm the accuracy, the Student method with 95% confidence and n-1 degrees of freedom was used. The calculated t values (table 3) for the studied concentrations presented values below the theoretical t (2,776), with no significant difference between the calculated t and the theoretical t. Noting that the concentrations studied are within the concentration range of amines in iron mining effluents.

Table 3. Recovery of EDA 3B amine standard solutions added to the samples and analyzed by the Bromocresol Green method. (n = 5) Example 3: Flotation Tests Flotation tests were made where the products were quantified by the bromocresol green and ninhhydrin methods. In the flotation tests 4 products were obtained, two solids and two liquids, which are presented in table 4. In the flotation tests performed the amine dosage was 40 g / t, which corresponds to 46 mg of added amine. For the bromocresol green method the total recovery was 45.33 mg on average, which corresponds to an efficiency of 98.5%, while for the ninhhydrin method 22.09 mg of the total added was recovered, corresponding to at an efficiency of approximately 48%.

The results presented in table 4 show that the bromocresol green method is more efficient for the quantification of amines in iron ore flotation residues. The results of quantification in solid samples for both methods are quite discrepant and the deficiency seems to be not only in the method of quantifying ninhhydrin, but mainly in the form of extraction of amine from solid residue.

Table 4. Extraction yield for bromocresol and ninhhydrin green method.

Despite being widely described in the literature, the ninhhydrin method was inadequate for amine quantification, especially in solid flotation samples. The bromocresol green method presented better accuracy and precision than the ninhhydrin method.

Thus, the proposed method of quantifying fatty amines from effluents generated by the iron ore reverse flotation process using a colorimetric technique containing bromocresol green is a more efficient method.

Claims (4)

1. Method of quantifying amines in iron ore flotation residues by colorimetric technique characterized by using bromocresol green as an organic dye Method for quantification of amines in iron ore flotation residues by colorimetric technique according to claim 1, characterized by quantifying fatty amines and etherines. Method for the quantification of amines in iron ore flotation residues by colorimetric technique according to claim 1 or 2, characterized in that the reaction between amine and bromocresol green occurs at pH 3 to 6, especially pH = 5. , forming a monoamine salt. 4. Use of the colorimetric technique for amine quantification characterized by quantifying fatty amines from effluents from the iron ore reverse flotation process using bromocresol green as an organic dye.