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THE BASIC MAINTENANCE OF WORK

In vvedeniiobosnovana an urgency of a theme of the dissertation, the short review of a modern condition of a problem of electrocatalysis and kompleksoobrazovanija in systems «nickel (II), cobalt (II) - eriochrome black T» is yielded, are formulated the purpose and work problems, protected positions, otme'che'ny scientific novelty and the practical importance of work are presented.

In the first glavepredstavlen the state-of-the-art review devoted to the analysis of works on kompleksoobrazovaniju and electrocatalysis of azo compounds with ions of metals, and also works on balance studying kompleksoobrazovanija in systems «metal - a ligand» on the basis of catalytic kinetic currents.

In the second glaveizlozheny the basic receptions of experimental studying of catalytic currents of systems «nickel (cobalt (II) - eriochrome black T» and instrumentation applied during the analysis, and also research of process of electrocatalytic restoration of systems «nickel (II), cobalt (II) - eriochrome black T» on a mercury dripping electrode and on steklouglerodnom an electrode is carried out, experimental data on studying of dependences of limiting catalytic currents of restoration of complexes of nickel (II) and cobalt (II) with eriochrome black T from concentration of a ligand, nickel (II), cobalt (II), ionic strength are presented, ion densities of hydrogen and of some other factors. Voltamperometrichesky measurements made on poljarografe ПУ-1. In researches by methods poljarografii as an indicator electrode used a mercury dripping electrode with characteristics: m = 1,192 mg/with, t1 = 3,65 with and m = 0,566 mg/with, t1 = 7,91 with at E =-1,0 Century As reference electrode the portable sated calomel electrode served, the salt bridge has been filled 3 % by th solution of agar in 1 MOLE/dm3NaNo3. In researches by methods by the adsorptive cathodic inversionnoj voltamperometrii as an indicator electrode served steklouglerodnyj an electrode, and a reference electrode - hloridserebrjanyj. Regeneration steklouglerodnogo an electrode made mechanically (dough GOI), then an electrode surface processed dimethyl ketone and ethanol. Values rn background electrolytes positioned by means of the liquid evaluator «Эксперт-001». All solutions prepared on bidistillirovannoj for water. As background electrolyte used NaCiO∣в a range of concentration from 0,05 to 1 MOLE/dm3. For stabilisation rn investigated solutions used boratnyj a buffer solution (0,2 MOLE/dm3H3Bo3i 2∙10 ' 3 MOLE/dm3Na2B4O710H2O) background electrolyte. Initial solution of eriochrome black T prepared shot dissolution in bidistillirovannoj for water daily. Solutions of ions of the metals, received by dissolution of shots NiCl2∙6H2O and the MOLE/dm3CtoSq ^^ in bidistillirovannoj to water, standardised kompleksonometricheski (komplekson III). Removed voltamperogrammy after pre-award deaeration of investigated solutions by a jet of the cleared nitrogen within 20 minutes with development of potential from 0 to-1,7 V.Spektrofotometricheskie researches of solutions of eriochrome black T against 0,2 MOLE/dm3NaClO4 (boratnyj the buffer) before long electrolysis were made on automatic spectrophotometer Specord 50 (Germany).

Ik-spectra of a solution of eriochrome black T against 0,2 MOLE/dm3NaClO4 (boratnyj the buffer) before long electrolysis removed on spectrophotometer Specord 75 IR (Germany).

On the river k.e. Eriochrome black T against boratnogo a buffer solution of background electrolyte NaClO4 is reduced at rn from 5,5 to 7,5 with formation of one poljarograficheskoj waves (drawing 1).

Half-Jarografichesky wave of electroreduction of eriochrome black T on the river ke. With increase rn it is moved to more negative potentials that specifies in participation of hydrions in electrochemical process (drawing 2).

Drawing 2 - the Graph of dependence E12эриохрома black T from rn (boratnyj the buffer) against 0,5 MOLE/dm3 of solution NaClO4при C ⅛∏ - = a 1,32∙10-MOLE/dm3

Drawing 1 - Voltamperogrammy eriochrome black T against 0,2 MOLE/dm3 of solution NaClO4при рН=6,8 (boratnyj the buffer) for lack of (1) and in the presence of ECHT (2-4): СЭчт=2,5 ∙ 106 MOLE/dm3 (2); СЭчт=5,0∙106моль/дм3 (3); СЭЧТ=9i9∙10-'моль/дм3 (4)

Basic feature of electroreduction of systems «nickel (II), cobalt (II) -

Eriochrome black T »consists that addition of eriochrome black T in the solutions containing ions of nickel (II) and cobalt (II), result ins to formation at the surface of an electrode, practically in double electric bed, complexes with various electrocatalytic, acid-base and complexing properties (drawings 3 and 4). At addition in the solutions containing ions of nickel (II) and cobalt (II), eriochrome black T at potentials of less negative, than waves of electroreduction of metals and more negative, than a wave of electroreduction of a free ligand occur poljarograficheskie the prewaves which height increases as with growth of concentration of eriochrome black T (drawings 3 and 4), and with growth of ion density of nickel (II) and cobalt (II) (drawings 5 and 6). For system «cobalt (II) - eriochrome black T» the catalytic current of a prewave starts to increase from value of a current of not catalytic discharge of akva-ions of metal D, as is shown in drawing 4.

Dependences of a limiting catalytic current on ion density of nickel (II) and cobalt (II) at rn = const and C ⅛∏∙ = const represent curves with a bend to an axis of abscisses (drawings 5, 6). Such kind of dependence at catalysis by eriochrome black T is conserved in a wide interval rn a solution 0,5 MOLE/dm3NaClO4. In growth of size of a limiting catalytic current with increase in ion density of metal at With l = const the theory catalytic poljarograficheskih currents at catalysis by the adsorbed ligand explains retardation by formation by ions of these metals elektrohimicheski inactive complexes in volume of a solution and in prielektrodnom bed.

Drawing 3 - Voltamperogrammy 5∙10-4моль/дм3 Ni (II) against 0,1 MOLE/dm3 of solution NaClO4при рН=6,8 (boratnyj the buffer) for lack of (1) and in the presence of ECHT (2-6): 2,5∙10-6моль/дм (2); 5,0∙10 "6mol/dm3 (3); 9,9∙10-5моль/дм3 (4); 3,4∙10-5моль/дм3 (5); 5,9∙10'smol/dm3 (; ν =0,5 В-с-1

Drawing 4 - Voltamperogrammy 1104mol/dm3 Co (II) against 0,5 MOLE/dm3 of solution NaClO4при рН=6,8 (boratnyj the buffer) for lack of (1) and in the presence of ECHT (2-7: 3,3∙10) "6mol/dm (2); бДЮ^моль/дм3 (3); 9,9∙10" 6mol/dm3 (4); 1,32∙10 ' 5mol/dm3 (5); 2,0∙10-5моль/дм3 (6);

3,210^5mol/dm3 (7); ν =0,5 В^с-1

Drawing 5 - Dependence of limiting catalytic current Iklсистемы «nickel (II) - ECHT» from ion density of nickel (II) against 0,5 MOLE/dm3 of solution NaClO4при various pH values (boratnyj the buffer): 6,0 (1); 6,4 (2); 6,8 (3); 7,0 (4);

7,2 (5); Secht = 1,010^4mol/dm3, E =-0,9 In

Drawing 6 - Dependence of limiting catalytic current Ikсистемы «cobalt (II) - ECHT» from ion density of cobalt (II) against 0,5 MOLE/dm3 of solution NaClO4 at various pH values (boratnyj the buffer): 6,0 (1); 6,4 (2); 6,8 (3); 7,0 (4);

7,2 (5); Сэчт=1,32∙10^5моль/дм3, E =-1,25 In

Character of influence of ion density of hydrogen on the limiting catalytic has been studied

Currents of systems «nickel (cobalt (II) - eriochrome black T» at catalysis by eriochrome black T on the river k.e 9

(Drawings 7, 8). Dependence of limiting catalytic currents of systems «nickel (II), cobalt (II) - eriochrome black T» from rn represents curves with a bend to an axis of abscisses. Decrease in limiting catalytic currents I* rn is connected with reduction with protonizatsiej a ligand, and it is possible to draw a conclusion, that anionic forms of eriochrome black T possess the maximum catalytic activity. At rn above 7 in prielektrodnom bed there is an inhibition poljarograficheskoj a catalytic prewave, that most likely is connected with strengthening protonirovannoj forms of eriochrome black T nv '. From literary data it is known, that at rn from 7 to 8 there is a formation of unstable complexes.

pH

Drawing 7 - Dependence Ik ι st rn against

0,5 MOLE/dm3 of solution NaClO4 (boratnyj the buffer) for system «Ni (II) - ECHT»: Svd> = 0,5103mol/dm3 (1); Smj = 1,0103mol/dm3 (2); Smda = 2,010^3mol/dm3 (3);> zd) = 3,0103mol/dm3 (4); Smdo = 5,0103mol/dm3 (); E =-0,9 In, Setg = 1,010^4mol/dm3

rn

Drawing 8 - Dependence Ik ι from rn against

0,5 MOLE/dm3 of solution NaClO4 (boratnyj the buffer) for system «Co (II) - ECHT»: ССад=0,8∙10-4моль/дм3 (1); ССад=2,6 ∙ 104 MOLE/dm3 (2); Ссад=5,0-10-4моль/дм3 (3); ССад=9,0∙10^4моль/дм3 (4); SSad = 1,210^3mol/dmr); E =-1,25 In, Сэчг=1,32∙10^5моль/дм3

The analysis of electrocapillary curves in drawing 9 has shown, that reduction of time of a life of a drop speaks about adsorption of a product of restoration of eriochrome black T on a mercury dripping electrode, and at introduction of ions of nickel (II) in a solution the further reduction of time of a life of a drop is observed, that can speak about stronger adsorption on a surface of mercury with nickel traces (). For system «nickel (II) - eriochrome black T» is absent direct adsorption of volume complexes of metal with a ligand-catalyst prior to the beginning of restoration of eriochrome black T. At the same time the raised ion density of nickel (II) leads practically to repressing of the adsorptive effect of a free ligand, but it does not influence electrocatalytic effect of the adsorbed ligand in the field of potentials catalytic poljarograficheskoj prewaves.

Drawing 9 - Electrocapillary curves of a mercury electrode of a buffer solution

0,2 MOLE/dm3NaClO4 (1) at рН=6,8; +C ⅛∏ - = 5,0∙10 ' 5mol/dm3 (2); +CN (∏) = 5,0 ∙ 104 MOLE/dm3 (3)

For charge definition elekroakivnyh the complexes formed on the river ke at catalysis by eriochrome black T, influence of concentration of background electrolyte NaClO4на limiting catalytic currents of systems «nickel (II), cobalt (II) - eriochrome black T» (drawings 10, 11) is studied. Observable decrease in a catalytic current with growth of concentration of background electrolyte NaClO4 at catalytic elekrovosstanovlenii systems «nickel (II), cobalt (II) - eriochrome black T» on the river ke. It is caused first of all by influence of a structure of double electric bed, that is corresponding influence ψ1 - potential for speed of superficial chemical reactions of formation of catalyticly active complexes of nickel (II) and cobalt (II) c the ligand adsorbed on an electrode eriochrome black T. With increase in ionic strength process of electroreduction of complex in system «nickel (II), cobalt (II) - eriochrome black T» is facilitated also potential of catalytic half wave Ek12сдвигается in cathodic area of potentials that is characteristic for processes with previous protonizatsiej.

Drawing 10 - Influence of concentration background

Drawing 11 - Influence of concentration background

In the third glaveprovedyon the analysis of the experimental data describing balance kompleksoobrazovanija and electrocatalysis of systems «nickel (II), cobalt (II) - eriochrome black T» in prielektrodnom bed and on an electrode surface, are positioned composition, stability, kinetic parametres of superficial reactions of formation of catalyticly active complexes and mechanisms of electrocatalytic process in systems «nickel (II), cobalt (II) - eriochrome black T».

Being based on the concept of series-parallel superficial reactions kompleksoobrazovanija the following mechanism of development of electrocatalytic process (1) in systems «nickel (II), cobalt (II) - eriochrome black T» has been offered:

Where j - a charge partially or completely deprotonizirovannoj ligand molecules in prielektrodnom

Bed.

There are two alternative mechanisms of the adsorptive concentrating: adsorption of electroreactive "volume" complexes without change of coordination sphere from prielektrodnogo bed and concentrating of complexes on an electrode on the mechanism a ligand-induced adsorbtsiikotorye also are responsible for the observed

Electrocatalytic effect of eriochrome black T. In the field of potentials of a limiting catalytic current of a prewave provided that ligand adsorption submits Henry's to linear isotherm, speed of catalytic electrode process (1) is described by the kinetic equation:

. The estimation of values of constants of stability in prielektrodnom bed on a limiting catalytic current in systems «nickel (II), cobalt (II) - eriochrome black T» has been made with use of two theoretical models based on electrocatalysis of ions of nickel (II) and cobalt (II) adsorbed on river k.e. A ligand under condition of Sm>> Q. In this case the second stage in the resulted schema can be neglected, and the equation (2) takes a form:

On the basis of the schema (1) and J.I.Turjana and N.K.Strizhova offered in work of the theoretical kinetic model based on braking of catalytic process with increase of concentration of metal for the account of linkage of a part of a ligand-catalyst in a complex ∖B ∖, H, B1 J and to decrease in active concentration of ligand HiBjadc, values of a conditional constant of stability of corresponding complexes of nickel (II) and cobalt (II) with eriochrome black T for various values rn investigated solutions (table 1) have been defined.

The alternative method of a finding of values of conditional constants of stability of the complexes, N.K.Strizhova offered in works, is based on the theoretical kinetic model describing dependence of the sum of limiting catalytic currents from concentration of a ligand - of the catalyst. The offered theoretical dependence

At absence kompleksooboazovanija in solution volume should coincide and at its construction in koordinatahodnako ravenstvdlja two concentration With ^

It is observed at different concentration Cl, On the basis of the dependence analysis «the limiting

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protonirovannyh ligand forms. The estimation of a constant of stability for composition complexes 1:2 the yielded method has shown its inconstancy which is falling outside the limits an error of a method, i.e. formation of complexes of such composition in investigated conditions can be excluded. In systems «nickel (II) - eriochrome black T» and «cobalt (II) - eriochrome black T» it is possible to explain comparative affinity of values of constants of stability of complexes formation in corresponding metallokompleksah chelated structure, as well as in case of volume complexes of metals with eriochrome black T.

Table 1 - Dependence of conditional constants of stability of complexes from rn

Calculated on the basis of the linear graph (drawing 12) values

Concentration constants of stability of complexes of ions of nickel (II) and cobalt (II) with eriochrome black T, and also the mixed ionisation constants of ligand Kv double electric bed and on a surface of an electrode for systems «nickel (cobalt (II) - eriochrome black T» are resulted in table 2. Values of the mixed ionisation constants of ligand Kv double electric bed and on

Drawing 12 - Dependence (’ Dsl from from an + on Ur. (5): «Co (II) - ECHT» (a number 1),

«Ni (II) - ECHT» (a number 2); on Ur. (: «Co (II) - ECHT» (a number 3), «Ni (II) - ECHT» (a number 4)

Surface of an electrode for systems «nickel (II), cobalt (II) - eriochrome black T» is a little above value of a thermodynamic ionisation constant protonirovannoj the form of eriochrome black T (К2 = 3,98∙10-7) in solution volume. It allows to assume, that in electrode process by catalyticly active form of a ligand-catalyst form H2В-дс is. Thus, a field

Electrode slightly influences a protolytic equilibrium (1) in a plane close to external plane Gelmgoltsa. It is possible to notice also, that for system «cobalt (II) - eriochrome black T» influence of ion density of hydrogen on a conditional constant of stability of a complex less considerably, than for system «nickel (-eriochrome black T».

Table 2 - Values of concentration constants of stability of complexes and the mixed ionisation constants of a ligand in double electric bed and on an electrode surface

Proceeding from the received values of the mixed ionisation constants of a product of restoration of eriochrome black T (table 2) on the equation (7) value of an ionisation constant of a ligand has been found in systems «nickel (II), cobalt (II) - eriochrome black T» equal To =, 0 10-7 MOLE/dm3 (rk ≈ 622):

At very low concentration background elektrolitavozmozhnoe

kompleksoobrazovanie in solution volume practically does not influence speed of electrocatalytic process. Hence, it is possible to neglect influence of ionic strength on a stability constant i a kinetic constant of a superficial catalytic reaction k1и the kinetic equation (2) it is possible to lead to a kind:

Where її - effective parametre in the kinetic equation (10).

The analysis of this dependence for systems «nickel (() - eriochrome black T» has shown cobalt, that the function inclination lg Z from ψ1 - potential priprakticheski is equal 17 В-1. It means, that

Boundary space charge of reacting particles (z = + zM = +1), a charge of the adsorbed form of a ligand -

The catalyst =-1, and a parity of reacting particles in catalyticly active complex equally 1:1. Hence, for systems «nickel (II), cobalt (II) - eriochrome black T» against boratnogo buffer solution NaClO4в skorostopredeljajushchej stages of superficial reaction kompleksoobrazovanija with ions of nickel (II) and cobalt (II) should participate adsorbed on the river ke. A product of restoration of eriochrome black T H2В-дс under the schema:

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The quantitative estimation of the superficial nature of electrocatalytic reactions in systems «nickel (II), cobalt (II) - eriochrome black T», allowing to obtain data about the nature of reacting particles on stoichiometry of volume and superficial reactions kompleksoobrazovanija, was made by means of the kinetic equation (12) received on the basis of transformation of the kinetic equation (2):

Where and equilibrium concentration of a ligand-catalyst in prielektrodnom bed with the account najde'nnyh sizes βλ and To ’ has been found earlier on the equation:

Kinetic parametres a'и bпараллельных superficial reactions kompleksoobrazovanija in systems «nickel (II), cobalt (II) - eriochrome black T», found on the basis of the analysis line'jnyh dependences of function of limiting catalytic current Y on equilibrium concentration of a ligand [/■], are resulted in table 3. Dependences of parametres a'и bв systems «nickel (II), cobalt (II) - eriochrome black T» from a structure of double electric bed (ψ1 - effect) as follows from drawing 13, will be co-ordinated with the theory poverhnosdnyh currents at catalysis by the adsorbed ligand.

Table 3 - Kinetic parametres of parallel superficial reactions kompleksoobrazovanija in systems «nickel (II), cobalt (II) - eriochrome black] T»

Dependence lg a'от ψ1 - potential in systems «nickel (II), cobalt (II) - eriochrome black T» corresponds to a boundary space charge of reacting particles in catalyticly active

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Drawing 13 - Dependence of kinetic parametres lg and ' and lg bст ψ1 - potential against boratnogo buffer solution NaClO4 (0,05 - 1 MOLE/dm3) at рН=6,8 for systems «nickel (II) - ECHT»: lg and (1), lg b (3), Sed = 5,0∙10-4моль/дм3, E =-0,9 In; and «cobalt (II) - ECHT»: lg and (2), lg b (4), Ssad = 1,0∙10-4моль/дм3, E =-1,25 In

The analysis of influence of ionic strength on catalytic currents of systems «nickel (II), cobalt (II) - eriochrome black T» has revealed presence previous protonizatsii eriochrome black T on the river k.e. Taking into account the positioned charge adsorbed on the river k.e. A ligand (zL =-1) which proves to be true the spectrophotometric analysis data, previous formation of catalyticly active complexes protonizatsiju a ligand can present in the form of two stages (15, 16), including formation of the intermediate tsvitter-ionic form of ligand NzVyo (15) at an electrode surface:

Analyzing the schema (1) with the account of the received data about values of kinetic parametres of parallel superficial reactions kompleksoobrazovanija, composition of complexes, a boundary space charge of reacting particles, a ligand ionisation constant in double electric bed and on electrode surfaces, interpretation of the mechanism of electrocatalytic process in systems «(II) - eriochrome black T» (17) it is possible to present nickel in the form of two series-parallel superficial chemical reactions of formation of catalyticly active complexes:

In systems «cobalt (II) - eriochrome black T» (18) it is possible to present the mechanism of electrocatalytic process in the form of two series-parallel superficial chemical reactions of formation catalyticly active komplekso

In dissertational work possibility of application of catalytic currents of system «nickel (II) - eriochrome black T» for definition of ions of nickel () in a mode of the adsorptive cathodic inversionnoj voltamperometrii on steklouglerodnom an electrode (table 4) is shown.

Table 4 - Results of definition of nickel (II) in the presence of eriochrome black T on steklouglerodnom an electrode in modelling solutions (Р=0,95)

Conclusions

1. The catalytic effect (poljarograficheskaja a prewave) is found out at electrochemical restoration of ions of nickel () and cobalt (II) in the presence of eriochrome black T on the mercury dripping electrode, caused by formation and the subsequent electroreduction of the adsorbed electroactive complexes.

2. Values of constants of stability of complexes of nickel () (β1 = 730 dm3/MOLE) and cobalt (II) (β1 = 1450 dm3/MOLE) with eriochrome black T are defined and value of an ionisation constant of the equilibrium form of a ligand-catalyst (rk ≈ 6,22) in electric field of an electrode with use of two theoretical kinetic models based on the analysis of dependences of a limiting catalytic current of restoration of ions of nickel (II) and cobalt (II) c adsorbed on river ke is received. A ligand.

3. On influence of a structure of double electric bed ^-effect) for speed of superficial chemical reaction of formation of electroreactive complexes of nickel (II) and cobalt (II) with adsorbed on the river ke. Eriochrome black T defines a boundary space charge of the reacting
частицI, and also a charge of catalyticly active form of a ligand-catalyst zL =-1.

4. Kinetic laws of electrocatalytic restoration of ions of nickel (II) and cobalt () are positioned. The estimation of composition of catalyticly active complexes in systems «nickel (II), cobalt (II) - eriochrome black T» is yielded. In system «nickel (II) - eriochrome black T» catalyticly active two complexes with adsorbed on the river k.e are formed. A product of restoration of eriochrome

5. Mechanisms of electrode catalytic reactions of electrochemical restoration of ions of nickel (II) and cobalt (II) and their complexes with eriochrome black T on the river k.e are positioned. On the basis an adsorption ligand-induced. It is possible to present electrocatalytic process in the form of two series-parallel superficial chemical reactions of formation of catalyticly active complexes. In system «nickel (II) - eriochrome black T» -

6. It is shown, that the tsvitter-ionic form of eriochrome black T takes part in formation of catalyticly active complex in system «cobalt (II) - eriochrome black T»

7. Naosnovanii basic research of catalytic currents of electrochemical restoration of system «nickel (II) - eriochrome black T» in a mode of the adsorptive cathodic inversionnoj voltamperometrii on steklouglerodnom an electrode their operability for voltamperometricheskogo definitions of ions of nickel (II) is shown.

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A source: ABRAMOVA NATALIA STEPANOVNA. ELECTROCATALYTIC REACTIONS of COMPLEXES of NICKEL (II) And COBALT (II) With ERIOCHROME BLACK T ON the MERCURY DRIPPING ELECTRODE. The dissertation AUTOABSTRACT on competition of a scientific degree of a Cand.Chem.Sci. Krasnodar - 2017. 2017

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