Method of extraction and detection of iron (iii) in water solutions

FIELD: chemistry.

SUBSTANCE: in order to extract iron (III) from water solutions diphenylguanidine (DPG) is applied as the first organic reagent. As the second organic reagent, salicylic acid (SA) is applied, and as solvent of organic phase chloroform is applied. In organic phase complex with molar component ratio DPG: Fe3+:SA, equal 1:1:1, is extracted. Process of iron (III) extraction is carried out at medium acidity pH=1.5-2.5 with the following detection of iron (III) by trimetric method.

EFFECT: invention makes it possible to increase selectivity and simplify process of extraction and detection of iron from water solutions.

2 cl, 5 dwg, 1 ex

 

The invention relates to the field of analytical chemistry, in particular to methods of separation and determination of iron(III) in aqueous solutions, salts of metals.

The known method acttraction-photometric determination of iron, based on the formation of complex compounds of iron with a reagent extraction in the organic phase and the measurement of the optical density of the extract, and as a complexing reagent is used as trichloracetic sodium in a weakly acidic environment (pH of 2.8-3.2 m), and the extraction is carried out with methylethylketone (and.with. The USSR №971802; C01G 49/00, G01N 21/77, B01D 11/04; publ. 07.11.82, bull. No. 41).

The disadvantage of this method is the low selectivity and sensitivity for determination of iron due to use as extractants of higher alcohols and tributyl phosphate. The use of methylethylketone narrows the optimal range of pH values. Also the disadvantage of this method is the poor solubility of methylethylketone in the water.

The known method of extraction-photometric determination of iron, based on the formation of triple colored complex compounds of iron - on-phenanthrolin - organic reagent, the organic reagent is used undiluted pelargonium acid, which is both a reagent and extractant (and.with. The USSR №880989; C01G 49/00, G01N 21/27, B01D 11/04; publ. 15.11.8, Bul. No. 42).

The disadvantage of this method is the use as an organic reagent pelargonii acid, the solubility of which is 0.026 g in 100 g of water. Also pelargonia acid volatile with water vapor, which can lead to significant errors of determination.

The closest in technical essence to the present invention is a method of determining iron in the metals, their oxides, salts and alloys, including masking of interfering elements, the introduction of organic reagents, extraction of the formed complex with chloroform and subsequent spectrophotometrically, characterized in that for the purpose of increase of accuracy of definition and simplify the process as a masking substance use glycine, and organic reagent - 3-nitroglycerin and diphenylguanidine (and.with. The USSR №1125542; G01N 31/22, B01D 11/04, publ. 23.11.84, bull. No. 43).

However, the known method is the prototype has a low selectivity of reactions and time-consuming, since it is necessary to vary the conditions of the definition and the use of masking agents to eliminate this deficiency.

The task of the invention is to increase the selectivity and to simplify the process of determining microsoldering iron(III) in aqueous solutions.

The problem is solved with the features specified in the 1st paragraph of the formula Fig�t, in common with the prototype, such as a method of separation and determination of iron(III) from aqueous solutions using as the organic reagent of diphenylguanidine, and distinctive essential features, such as the second organic reagent is salicylic acid, and as a diluent of the organic phase chloroform with medium acidity pH=1.5 to 2.5 with subsequent determination of iron(III) titrimetric method.

According to paragraph 2 of the claims in an organic microphase extracted complex with molar ratio of components FGD:Fe3+:IC equal to 1:1:1.

This object is achieved in that the optimal conditions for the formation of microphase in the system diphenylguanidine - salicylic acid - HCl - water, and extraction in complex compounds of iron(III).

The above set of essential features allows to obtain the following technical result - increasing selectivity and simplifying the process of determining microsoldering iron(III) in aqueous solutions.

The proposed method is illustrated by the following graphs.

Fig.1. The distribution of iron ions(III) in the FGD system-SC-HCl-H2O depending on the acidity of the water environment (CFGD=CSC=0,2 mol/l, CFe=0.01 mol/l, Vtotal=20 ml)

Fig.2. The distribution of iron ions(III) in the FGD system-SC-HCl-H O depending on the concentration of salicylic acid (CHCl=0.05 mol/l, WithFGD=0,2 mol/l, CFe=0.01 mol/l, Vtotal=20 ml)

Fig.3. The distribution of iron ions(III) in the FGD system-SC-HCl-H2O depending on the concentration of the FGD (CCHl=0.05 mol/l, CCK=0,2 mol/l, CFe=0.1 mol/l, Vtotal=20 ml)

Fig.4. The dependence of the ratio of FGD:extractable Fe in the complex from the composition of a motorized solution

(∑C(FGD+Fe)=0.1 mol/l, CCK=0,2 mol/l, CHCl=0.05 mol/l, Vtotal=20 ml)

Fig.5. The dependence of the ratio SC:extractable Fe in the complex from the composition of a motorized solution

(∑C(SK+Fe)=0.1 mol/l, WithFGD=0.1 mol/l, CHCl=0.05 mol/l, Vtotal=20 ml)

Organic microphase is formed in the temperature range of 50-95°C. With increasing temperature the process of formation of two-phase equilibrium is accelerated. Upon cooling after extraction of the organic phase, which is the extractant, freezes, however, there is a high degree of extraction of ions in iron(III).

The formation and extraction of the extracted complex of Fe is in a narrow range of concentrations of HCl (0,025-0,1 mol/l). Maximum extraction of iron is observed in the range of 0.05-0.15 mol/l HCl [Fig.1].

The dependence of extraction of iron from the concentration of salicylic acid (SA) for CHCl=0,05 mol/�. The graph of the curve EFe, % - CSCit is seen that the maximum value of the degree of extraction of iron is 95% and observed at CSC=0.1 to 0.15 mol/l [Fig.2].

At optimal concentrations of IC and HCl investigated the effect of the concentration of diphenylguanidine (FGD) on the degree of extraction of iron ions. Maximum extraction of iron is observed when CFGD=0.1 mol/l and CHCl=0,05 mol/l and 91% [Fig.3].

Thus, the optimal conditions for the extraction of iron salicylic acid in the presence of diphenylguanidine should be considered: CHCl=0,025-0,15 mol/l, WithFGD=0,1-0,25 mol/l, WithSC=0.1 to 0.2 mol/l (in the total volume of the extraction system 20 ml).

The sensitivity of detection of 0.25 mg/ml For the determination of iron in the organic phase formed by the UK and FGD, organic microphase was diluted with 3-5 ml of chloroform. Next, a chloroform solution was poured into a titration flask. The iron content was determined by direct complexometric titration in an acidic environment. At optimal concentrations of IC and HCl was determined by the ratio of FGD:Fe, which was equal to 1:1. Thus, one atom of iron in the complex compound has one molecule FGD [Fig.4].

The ratio Fe:the UK also was evaluated using a motorized series. As can be seen, the ratio Fe:the UK is 1:1. Thus, with�Tav extractable complex iron compound includes one molecule of salicylic acid to one iron ion [Fig.5].

Thus, in the organic microphase extracted complex with a molar ratio of FGD:Fe3+:IC equal to 1:1:1. Most likely, in the extraction process produces iron salicylate [FeSal·FGD]X2where X - is an inorganic anion (in the acidic environment of the iron ion is coordinated by one molecule of the UK), which Salvatores one molecule of FGD.

The obtained data on the composition otvlekaeshsja complex compounds of iron allow us to offer the following equations its extraction into microphase and process of education itself microphase:

FGD+HSal↔(DPG·H)Sal,

FeSal2++2-+(DPG·H)Sal=[FeSal·FGD]X2+HSal.

Example. For the determination of iron(III) in the stratified system FGD-SC-HCl-water did the following. Sample SK, weighing 0.55 g and DPG, weight 0.85 g was placed in a vial of 20 ml, created an HCl concentration of 0.05 mol/l, was added ferric chloride(III) (1·10-4-2·10-2mol/l) and adjusted with water to a volume of 20 ml. Vial was placed in a water bath and heated for 20-30 min. Then the whole system was cooled to room temperature. The aqueous phase was poured into a titration flask and titrated with EDTA until a yellow color. The resulting organic phase was diluted with 3-5 ml of chloroform, and then transferred to a titration flask and titrated with EDTA.

Thus, the proposed method of allocation and ODA�fission of iron(III) in aqueous solutions by diphenylguanidine, it has high sensitivity, it has a good reproducibility and selectivity.

1. A method of separation and determination of iron (III) from aqueous solutions using as the organic reagent of diphenylguanidine, characterized in that as the second organic reagent is salicylic acid, and as a diluent of the organic phase is chloroform with medium acidity pH=1.5 to 2.5 with subsequent determination of iron (III) titrimetric method.

2. A method according to claim 1, characterized in that the organic microphase extracted complex with molar ratio of components FGD:Fe3+:IC equal to 1:1:1.



 

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