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THE BASIC MAINTENANCE OF WORK

In introduction the work urgency, scientific novelty and the practical importance are proved.

In chapter 1 the Review of references and research problem statement is yielded the analysis of references, theoretical positions are considered and the basic methods of research of kinetics of processes of dissolution are analysed, necessity of application of a method of a rotating disk as the most perfect is proved at studying of kinetics of processes of dissolution.

Modern methods of planning of experiment and mathematical modelling of kinetics of processes of dissolution are described. It is shown, that the combination of a method of a rotating disk to possibilities of mathematical planning is effective at construction of kinetic models of processes of dissolution. Definite purposes and research problems.

The second chapter Methods of research of processes of dissolution of nickelous sulphide (II) is devoted the characteristic of samples, the description of techniques of carrying out of experimental researches, processings of their results and reception of mathematical models. At work performance methods of a rotating disk, peremennotokovoj poljarografii, the atomic absorption analysis are used. To studying of structure and a condition of a surface of samples are applied
Methods rentgenofazovogo the analysis (RFA), rentgenofotoelektronnoj spectroscopy (RFES) and scanning zondovoj microscopies (SZM).

In the third chapter Hydrolytic and oxidising dissolution of nickelous sulphide ( experimental results are presented and their discussion is made. Dependences of specific speed of dissolution of nickelous sulphide (II) in solutions H2SO4, H2O2, HNO3от concentration of a reagent, temperatures, rn a solution, intensity of agitating and duration of interaction are studied. Are received

Mathematical models of processes their physical and chemical interpretation also is made, interaction modes are positioned, revealed

Limiting stages. The proved schemas of interaction are offered.

Nickelous sulphide (II) is synthesised by a method of sedimentation from solution NiCl2 hydrogen sulphide. According to RFA (fig. 1) as a part of the synthesised nickelous sulphide (II) the basic component is millerit, but is present as well polidimit Ni3S4 (to 8 %).

At duration

Disolutions more than 100 mines in all cases observed a linear relation of nickel passing in a solution (Q, the MOLE/dm2) from time (τ,). For the chosen reagents (H2SO4, H2O2,

Fig. 1 - Difraktogramma the synthesised nickelous sulphide

HNO3) originally investigated dependences of specific speed of transferring of nickel in a solution (W, the MOLE/dm2-c) from molarity of an equivalent of these connections (fig. 2). Then chose ranges of sizes of influencing factors (Sn, temperatures T 0К, rotating speeds of a disk ω с-1) and using a method of full factor experiment (PFE) built polynomial models of investigated processes. For simplification of a problem of construction of model as response function took lg (W), and influencing factors are presented in a kind lg (C), 1/T and lg (ω).

For area of low concentration a chamois

Acids from 0.006 till 0.05 a mole-ekv/dm3 in the range of temperature 293-323 To, at rotating speed of a disk 1.6 and 10 с-1 according to PFE 2 are carried out experiences on

Fig.

2 - Dependences lgW-lgC ∏ at 298 To and ω =10 с1 to definition of sizes W the polynomial model of a kind also is calculated:

Hypothesis check about adequacy of model by Fisher's criterion is made and is recognised, that the polynom (1) adequately represents studied process.

Transferring from the coded values to natural variables will transform model (1) to the equation of speed of process of dissolution of nickelous sulphide in H2SO4:

Order on acid is close to zero, rotating speed of a disk does not render influence on speed of process. A dissolution kinetic constant (K298) counted from the equation (2) under a condition: Sn = 1 mole-ekv/dm3, ω =1 с-1 and T = 298 K.Ona it is equal 4 ' 9-s-1. Empirical value of critical increment of energy (Ea) counted from temperature dependence of a kinetic constant of process. It makes 16.4 0.8 a kdzh/MOLE. The analysis of the basic kinetic parametres shows, that process proceeds in a kinetic mode.

For more concentrated solutions of sulfuric acid in a range of values of influencing factors (0.5 ≤ With ≤ 5.0, 293 ≤ T ≤ 323 To and 1.6 ≤ ω ≤ 10 с-1) on the procedure described above the adequate model is received:

Order on H2SO4практически the zero; rotating speed of a disk does not influence speed of process; Еа=15.4 yo 0.6 kdzh/MOLE; К298 = 8 at 298 To.

7


Model (3) analysis shows, that process of dissolution NiS in sulfuric acid at its concentration from 0.5 to 5 mole-ekv/dm3 kinetic.

The surface of response W depending on T and Sn on model (3) is presented on fig. 3.

In the field of high concentration the greatest size of speed (16.1∙10 ' 9 mole-dm ' 2-s-1) is reached at

The maximum values of concentration and fig. 3 _ Dependence of speed

Temperatures (accordingly at With = 5 dissolutions NiS from C11 (H2SO4) and T

molyekv/dm3 And Т=323К).

The prospective mechanism of interaction of nickelous sulphide (II) c sulfuric acid solutions includes stages of hydration and the subsequent protonizatsii gidratirovannoj surfaces-that the following schema reflects:

The further stage of process of dissolution is hydrolytic interaction protonirovannoj surfaces with hydroxonium ions, with the subsequent formation of the unstable connections decaying on hydrogen sulphide (H2S) and H2O. The stage of hydrolytic decomposition of products of hydration of a surface presumably is limiting:

It, possibly, includes adsorption H3O+на protonirovannoj sulphide surfaces. Zero order on sulfuric acid at its concentration above 1 molyekv/dm3 shows, that as the slowest stage adsorption of hydroxonium ions acts, and process proceeds in the conditions of the adsorptive saturation.

8


The discussed mechanism is hydrolytic.

Process is not accompanied by sulphide sulphur oxidation that is confirmed by results

Surface researches

Sulphide method RFS (fig. 4) on which there is no element sulphur.

Interaction NiS with

Fig. 4-Rentgenofotoelektronnyj a spectrum solution H2SO4сопровождается

Surfaces NiS of nickel after contact to surface structural change

H2SO4 (Сн=1 the MOLE/dm3, 298 To, τ = 30 mines) sulphide. Skany SZM surfaces to

Contact to sulfuric acid and after interaction with it are presented on fig. 5. Decrease in clearness of borders of grains in the sample, connected, possibly, with diffusion on a surface of finished products of interaction is observed. A centre roughness of a surface

Increases in 4,8 times. However, it does not result in to growth of specific speed of dissolution in due course.

Behaviour NiS is investigated in

Solutions Н2О2.

For strong dilute solutions of peroxide compound of hydrogen at at рН=2.5, Sn = 0.002 0.02 mole-ekv/dm3,

293 ≤ T ≤ 323 To and 1.6 ≤ ω ≤ 10 с-1

The adequate polynomial Fig. 5 - the Surface of sample NiS is received: the model transformed to the equation the initial sample; after

Speeds: interactions with H2SO4

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Rotating speed of a disk does not influence speed of dissolution; order on H2O2 is close to zero; К298=1.49 Ч0-9 моль09 dm-17 s-1; Ea = 10.2 0.1 кДж^моль-1. The Process conditions kinetic.

For more concentrated peroxide compound of hydrogen at Сн=0.25 - 2.5 mole ekv/dm3 at 293 ≤ T ≤ 323 To and 1.6 ≤ ω ≤ 10 с-1 the equation of speed of process looks like:

W = 8.31 • 10-1 • s0-1 • е1, "5 ω.)". (7)

Order on H2O2практически the zero; rotating speed of a disk does not influence speed of process; К298 = 7 ’ 17 ^ ’ 1, Ea = 11.7 0.2 kdzh/MOLE. Process of dissolution NiS in hydrogen peroxide compound proceeds in a kinetic mode.

The surface of response W depending on T and Sn on model (7) is presented on fig. 6.

For area of higher concentration H2O2наибольшая the size of speed (13) is reached at the maximum values of concentration and temperatures (at With = 2.5 molyekv/dm3 and Т=323). Degree of influence of factors in the considered areas of high and small concentration of peroxide compound of hydrogen on size of speed W nickelous sulphide disolutions decreases from concentration to temperature.

Necessary stage of this process is hydration with the subsequent protonizatsiej nickelous sulphide surfaces. Further nickelous sulphide dissolution at Sn2О2) 0.25 mechanism of dissolution the oxidising. In these conditions H2O2 exists in shape gidroksilgidroksonija, which is adsorbed (the schema 9) on a sulphide surface (a probable limiting stage). Process proceeds in the conditions of the adsorptive saturation (W~Ch0).

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According to (10) order on HNO3 it is close to zero; rotating speed of a disk does not influence speed of process; К298 = 1; Ea = 6.5 + 0.2 kdzh/MOLE. In the selected conditions process of dissolution NiS in HNO3протекает in a kinetic mode.

For more concentrated solutions HNO3при With = 0.5 - 3 MOLE/dm3, T = 323 - 293 To, and ω from 1.6 to 10 с-1 the equation of speed of dissolution NiS is received:

W = 3.3 ∙10-1 • s0-82~218z τ • e ' τω 0. (11)

Model (11) reflects interference of strength of acid and temperature. Order on acid changes from 0 at 293 To till 0.14 at 323 To is close to zero. Rotating speed of a disk does not influence speed of process. Ea increases in process of increase in strength of acid from 3.6 + 0.3 кДж^моль-1 at With = 0.5 MOLE/dm3 to 6.8 + 0.3 кДж^моль-1 at With = 3.0 MOLE/dm3. Process of dissolution NiS in HNO3протекает in

Kinetic mode.

Fig. 9 - Dependence of speed of dissolution NiS from C (HNO3) and T

The surface of response W depending on T and Sn on model (11) is presented on fig. 9. The greatest size of speed (5 molydm-2s-1) is reached at With = 3 MOLE/dm3 and Т=323 To.

The mechanism of process of dissolution NiS in dilute solutions HNO3является the hydrolytic. In it specifies also insignificant difference in sizes of specific speed for processes of dissolution NiS in sulfuric and azotic acids at C> 0.1 (at

С=0.01, Т=298 To and ω =10 с-1 for H2SO4 W = 2, and for HNO3

W = 3). A prospective limiting stage is adsorption

H3O+на gidratirovannoj and protonirovannoj sulphide surfaces.

The mechanism of process of dissolution NiS at C> 0.3 mol/dm3HnO3javljaetsja the oxidising. The first and necessary stage of process is hydration which follows protonizatsija to a reactionary surface. Then oxidation proceeds:

(-Ni-S - N +) tv + H3O ++ 2 NO 2 (ads) = Ni2 + (r-r) + 2 NO + S0 + 2^O. (12)

Limiting stage, possibly, adsorption NO2, formed as a result of decomposition HNO3 is.

The analysis of spectrum RFES (rice 10) at QHNO3) =1 MOLE/dm3 on a surface is formed

Element sulphur.

Dissolution NiS in hydrogen nitrate is accompanied

Structural change

Superficiality. A surface of the sample of nickelous sulphide after

Fig. 10 ' Rentgenofotoelektronnyj a spectrum of a surface of nickelous sulphide after contact with

HNO3при С=1 the MOLE/dm3, 298 To, τ = 30 mines

30 minute interactions about 1 MOLE/dm3 an acid solution at 298К it is investigated by method SZM semicontact atomno'silovoj microscopies. Centre aggregate size makes 13х6 μm in all samples. Occurrence of fields with the expressed borders on fig. 1 1 can be connected with sulphur sludging on a sulphide surface. However formation of sulphur does not result in to dissolution retardation. Dissolution result ins to increase in a roughness of a surface of sulphide in 52 times. However, it does not result in to growth of specific speed of dissolution in an experience current.

In the fourth chapter Influence of cations Fe3+и Cu2+на speed of dissolution of nickelous sulphide (II) in hydrogen nitrate experimental results are presented and their discussion is made.

Estimation of influence of concentration of cations Fe3+и Cu2 + for speed of process of dissolution NiS made in solutions HNO3 with concentration 1 MOLE/dm3 in the field of zero order on acid (fig. 2). As 12 addition in solution HNO3солей of iron () follows from fig. and coppers (II) result ins to sharp increase of speed of transferring of nickel in a solution. For both kinds of ions zero order on their concentration is noted at 0.004 mole-ekv/dm3.

Fig. 1 1 - the Surface of sulphide after with HNO3

For the purpose of reception of fuller information on process of dissolution NiS in

3 +

To hydrogen nitrate in the presence of cations Fe its mathematical model is constructed.

At CH (Fe3 +) = 0.004 mol'ekv/dm3, 0.5 ≤ C (HNO3) ≤ 3 MOLE/dm3, 323 ≤ T ≤ 293 To and 1.6 ≤ ω ≤ 10 с-1 the equation of speed of process of dissolution looks like:

022 W = 1.38 • 10-6 • Сα12 • e ~ - ω . (13)

Intensity of agitating does not influence speed of transferring of nickel in a solution; order on acid is close to zero; K298 = 1 ’

16-с ’ 1; Еа=5.60.3 a kdzh/MOLE. The kinetic mode of interaction is observed.

The surface of response W depending on T and With on model (13) is presented on fig. 13. In the field of concentration HNO3от 0.5 to 3 MOLE/dm3 the greatest size of speed (2) is reached at With = 3 MOLE/dm3 and Т=323 To.

The increase in speed of dissolution of nickelous sulphide is connected with catalytic influence of cations Fe, possibly, at the expense of simplification of electron transfer from gidratirovannoj surfaces millerita to oxidizer NO2. It is possible to present the prospective mechanism as follows. protonirovannaja the nickelous sulphide surface adsorbs ions Fe3 +:

obra


As a result, iron ions remain invariable, carrying out a role of oxidation catalyst of nickelous sulphide hydrogen nitrate.

For reception of kinetic model of process of dissolution of nickelous sulphide in the presence of cations Cu2+выбран a range of influencing factors (0.5 ≤ C (HNO3) ≤ 3 MOLE/dm3; 298 ≤ T ≤ 323 To; 1.6 ≤ ω ≤ 10.0 с-1). Ion density of copper in all experiences is constant - 0.002 mole-ekv/dm3. It corresponds to area of zero order on Cu2 + (fig. 12). The equation of speed of dissolution looks like:

Intensity of agitating does not influence speed of process; order on

To acid it is close to zero; K298 = 9

^-dm mole ’ ^-with ’ 1; Еа=3.60.3 a kdzh/MOLE.

The kinetic mode is observed

Interactions.

The surface of response W depending on T and With on model (16) is presented on fig. 14. In the investigated area in the presence of cations Cu2+наибольшая the size of speed (1 ’ 2 s-1) is reached at

Fig. 14 - Dependence of speed

Disolutions NiS from C (HNO3) and T, at C (Cu2 +) = 0.002 molyekv/dm3

C (HNO3) = 3 MOLE/dm3 and Т=323 To.

The increase in speed of dissolution of nickelous sulphide is connected with catalytic influence of cations Cu2 +. Assumed

The mechanism of interaction of nickelous sulphide (II) c hydrogen nitrate solutions in

Presence of cations Cu2+описывается it is similar above considered for Fe3 +.

The assumed schemas of the mechanism of dissolution millerita in hydrogen nitrate in the presence of ions Fe3+и Cu2+объясняют observable kinetic dependences.

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A source: PITCHUGINA Anna Igorevna. KINETICS of HYDROLYTIC And OXIDIZING DISSOLUTION of NICKELOUS SULPHIDE (II). The dissertation AUTOABSTRACT on competition of a scientific degree of a Cand.Chem.Sci. Tver - 2016. 2016

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