SU1684654A1 - Method of electrochemical determination of rhenium in the presence of vi group elements - Google Patents

Abstract

The invention relates to analytical chemistry, in particular to electrochemical methods for the separation of rhenium, and can be used for the analysis of rhenium alloys, copper and molybdenum concentrates, etc. The purpose of the invention is to increase sensitivity, accuracy and expressivity. and simplifying the method of determination. Recovery of rhenium is carried out in a single-chamber cell with sodium amalgam in a solution of 1-2 M NaOH. Anodic alternating current polarograms are recorded in the same solution in the potential range from -1.4 to -0.4 V. The rhenium concentration is determined from the height of the peak at a potential of 0.85 ± 0.05 V. Sn M. Analysis time 20 minutes. The presence of a 10,000-fold excess of W, Mo, Se, Cz, Te does not interfere with the determination. 2 tab., 1 Il. (Ls.

Description

The invention relates to analytical chemistry, in particular, to electrochemical methods of separation and determination of rhenium, and can be used in the analysis of various objects on the content of rhenium (rhenium alloys with various metals; copper and molybdenum production products — copper and molybdenum concentrates, dusts, butts; molybdenite and sulfide ores of complex composition).

The aim of the invention is to simplify the method, increasing its sensitivity, accuracy and expressness.

The invention is illustrated in the drawing.

Rhenium (VII) concentration of M is reduced in sodium amalgam reride in an alkali solution of 1-2 M concentration, in a single-chamber cell without

mixing to achieve a constant value of the redox potential -1.0 - -1.1 V (NASE). An alkaline solution of renide is directly graphed in the same cell. The determination of rhenium is carried out according to the height of the peak of anodic oxidation of rhenide, which is fixed on the alternating current polarogram.

The use of alternating current polarography makes it possible to reduce the detection limit of rhenium to M, i.e. increase the sensitivity of rhenium determination by more than an order of magnitude. The reduction of rhenium (VII) to reed directly by sodium amalgam in a single-chamber cell simplifies the process, eliminates the resistance of the diaphragm, which contributes to a significant acceleration of the process. For the quantitative reduction of rhenium (VII) to rhenide at its mol / l concentration, according to the prototype,

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more than an hour, while the proposed method-20 min.

Removal of polarograms in 1-2 M NaOH does not require additional electrolyte injection to increase the electrical conductivity of the solution.

The range of detectable rhenium concentrations is extended (10 7-5 10 4 M).

The registration of the anodic polarogram of the reed is performed on the PU-1 polarograph in an alternating current mode directly in the cell in which rhenium (VII) was reduced by sodium amalgam to rhenide in 1-2 M NaOH. The sweep speed of 5 mV / s, the current range, depending on the concentration of rhenium, varies from 25-100. Discharge is carried out from the potential of -1.4 V (NasA) into the anode region. Recording of the programs is carried out automatically on the PCB. The presence of elements of the sixth group does not preclude the quantitative determination of the rend by the polarographic method (Table 1). From tab. 1 that the results of the determination of rhenium by the polarographic method with its concentration in the range of

mol / l in the presence of elements of group VI are well reproducible. The relative error does not exceed 0.11. The only element of the sixth group, tellurium (IV), after reduction by amalgam to telluride, gives the peak of oxidation on the EFC. The peak potential of oxidation of telluride is 0.60 V (NACE), the peak potential of oxidation of rhenide is 0.85 V (NACE). The peaks are clearly separated, so tellurium does not interfere with the determination of rhenium within the concentration of rhenium mol / l.

The drawing shows an anodic alternating current polarogram of alkaline solutions containing adenide and telluride at a concentration of 10 mol / l (current range 100), where the following notation is used: 1 - Re (VII) mol / l; 2 - Te (IV) mol / l.

PRI me R. A 1.5% sodium amalgam, 45 cm of a 1 M solution of NaOH is introduced into a single-chamber cell and oxygen dissolved in alkali is removed by stirring the solution with an amalgam for 2 min. Next, rhenium (VII) solution is introduced to its mol / l concentration in the final volume (50 cmg) of the solution and the process of restoring rhenium (VII) into sodium rhenide with sodium amalgam is carried out without control, it is controlled by measuring the redox potential in the solution volume by amalgamated Pt microelectrode. The process is carried out until a constant value of the redox potential of -1 V (NaxKE) is reached, indicating the end of the process. The recovery time is 10 min. Further, in the same cell, the anodic polarogram of the oxidation of rhenide in alternating mode from –1.4 V potential (ASTC) to the anodic region is removed; a current range of 25, a sweep rate of 5 mV / s. At the height of the anodic peak of rhenide oxidation, fixed at a potential of 0.85 V (NEC), the rhenium content is calculated using a calibration curve.

The initial amount of rhenium is 9.3 μg. Found 9.3 mcg.

Other examples of the determination of rhenium in the presence of elements of the sixth group are given in Table. one,

A method of reducing rhenium (VII) to rhenide in a solution of 1-2 M NaOH with sodium amalgam followed by a polarographic (voltammetric) determination of the rhenide from its oxidation current on an EEC in the same 1-2 M NaOH solution in which the reduction of rhenium was performed (VII) , in the same cell, is simple, has a higher sensitivity (the limit of detection of rhenium M, instead of 210 M in the prototype).

The time spent on the recovery process is reduced by a factor of 2-3 compared with the prototype. The process is carried out without mixing (unlike the prototype). Polrography of rhenium (VII) solution in 1-2 M NaOH does not require the additional operation of introducing sodium chloride in 0.1-0.3 M NaOH (prototype conditions) to increase the conductivity of the solution. The elements of group VI (W, Mo, Se, Cr, Te) do not interfere with the determination of rhenium even in the 10,000-fold relation to rhenium.

Claims (1)

Invention Formula The electrochemical method for determining rhenium in the presence of Group VI elements, which consists in controlling the process of reducing rhenium (VII) to rhenium upon reaching a constant value of the redox potential and subsequent registration of the anodic oxidation polarogram, characterized in that, in order to increase the sensitivity and express determination, As well as simplifying spoob, the reduction of rhenium (VII) is carried out in a single-chamber cell with sodium amalgam in a solution of 1-2 M NaOH followed by recording of the anodic alternating current polarogram in the same in solution in the range of potentials from -1.4 to -0.4 V, and the concentration of rhenium is determined by the height of the peak at El -0.85 + 0.05 V. Table 1 Examples of the determination of rhenium by the oxidation current of rhenide by the polarographic method in an alternating current mode. Concentration of tungsten (VI), molybdenum (VI), selenium (VI) 10 mol / l, concentration of chromium (VI) and tellurium (IV) l-4 10 mol / l. Total volume 50 cm 0.45 0.55 0.65 0.15 0.85 0.95  Hhg W5 -E, B {Nasg e)