Recovery of Manganese and Zinc from Waste Dry Cell Powder
Part II: Experimental Design of Leaching by Glucose Containing Sulphuric Acid Solution
Ranjit K. Biswas*, Aneek K. Karmakar and Sree L.
Kumar
Dept. of Applied Chemistry & Chemical Engineering Rajshahi University
Rajshahi, Bangladesh [email protected]
Abstract-The factors effects in leaching of waste dry cell powder by glucose containing sulphuric acid solution have been determined by 24 factorial designs for both Mn and Zn dissolutions at leaching time of 1 h and pulp agitation of 300 rpm.
On abbreviating amount of glucose in g, strength of sulphuric acid in mol/L, volume of H2SO4 solution in mL and temperature in oC as G, S, V, and T, respectively; the designed model for Mn- dissolution from 5 g powder is:
Y (% Mn dissolved) = 29.16 - 1.28G - 0.135S + 0.053V + 0.11T + 0.994GS + 0.0066GV - 0.003GT + 0.021SV + 0.06ST + 0.0011VT - 0.0026GSV - 0.0086GST - 0.00016GVT
whereas, the same for Zn-dissolution from 5 g powder is:
Y (% Zn dissolved) = 30.37 – 0.56G + 3.0S + 0.049V + 0.14T + 0.004GV - 0.0057GT + 0.028SV + 0.034ST + 0.0012VT - 0.0016GVT - 0.00025SVT These equations are examined for comparison with experimental results and also used for optimization of factors. At optimized G = 0.5 g, S = 2 mol/L, V = 250 mL and T = 100oC, 5 g powder in 1 h at 300 rpm produces a solution containing (7.08±0.10) g/L Mn(II) and (2.20±0.06) g/L Zn(II) corresponding to almost 100% dissolution of both metal ions.
Index Terms — Waste dry-cell powder, factorial design, manganese, zinc, H2SO4, glucose.
I. INTRODUCTION
In Part I of this work [1], the waste single brand dry cell powder was characterized and found to contain (35.4±0.2) % Mn, (11±0.1) % Zn and 2.5 % Fe together with some Al, Si, K etc. Zinc was mostly present as Zn(ClO4)2.2H2O and ZnMn2O4 in hot water leached residue. It does not contain any MnO2 generally used in dry cell preparation; only Mn-containing phase identified was ZnMn2O4. It was believed that during hot water leaching, MnO2 oxidized ZnCl2 to Zn(ClO4)2 according to reaction: ZnCl2 + 16 MnO2 → Zn(ClO4)2 + 8Mn2O3. Mn2O3 so or otherwise produced (MnO2 + H2O + e → MnO(OH) + OH- followed by 2MnO(OH) → Mn2O3 + H2O) reacts with Zn(OH)2 to form ZnMn2O4 (Zn(OH)2 + Mn2O3 → ZnMn2O4 + H2O). The powder was not soluble in sulphuric or other acid
solution. However, it could be dissolved by sulphuric acid solution containing a reducing agent like glucose.
In the present work, the leaching of the powder by sulphuric acid-glucose mixture will be studied through a two- level four factorial (24) design [2-4], considering concentration of sulfuric acid (M), volume of sulfuric acid (mL), amount of glucose (g) and temperature (oC) as factors, with a constant leaching time of 1h and pulp agitation speed of 300 rpm for 5 g powder. The designed equation will be examined for comparison with experimental results and also be used for optimization of factors.
II. EXPERIMENTAL A. Materials
The waste dry cell powder is collected and processed for using in leaching, as described earlier [1]. A. R. grade chemicals of either E. Merck (Germany/India) or Loba Chemie (India) were used without further purifications. Glucose was a product of GSK (Bangladesh).
B. Leaching procedure
The leaching procedure is also described earlier [1]. An aliquot of leaching agent is taken in a 250 mL or 500 mL conical flask. A meter-long glass tube, wrapped with moist cloth acting as condenser, is placed tightly at the opening of the flask. It is immersed up to its neck in a large beaker containing boiling water; the boiling of water in the beaker and the stirring of mass in the conical flask are aided by magnetic hot plate.
Stirring speed is controlled at 300 rpm. When the solution in the flask reached the desired temperature, a weighed amount of waste powder is added; and the stirring and heating at the desired temperature are continued for a desired time (1 h). For leaching at lower temperature, thermostated water is circulated in the large beaker. After, leaching, the solution obtained on filtration is subjected for analysis of its Mn2+ and Zn2+ contents.
International Conference on Materials, Electronics & Information Engineering, ICMEIE-2015 05-06 June, 2015, Faculty of Engineering, University of Rajshahi, Bangladesh
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ISBN 978-984-33-8940-4
C. Analytical
The total metal ion concentration is determined by EDTA titration [5a]; while the concentration of Mn(II) alone is determined by the colorimetric method at 545 (Erma, AE 300, Japan) after formation of KMnO4 by oxidation with HNO3- KIO4 [5b]. The difference gives the concentration of Zn(II).
Occasionally, the concentrations determined by these methods are checked by estimating them using AAS (Shimadzu AA- 6800 spectrophotometer).
D. Statistical Relations Used
The average yield, ̅ and the variance for each trial; the pooled variance ( ), standard deviationpooled, [MIN] and [MINC] are calculated by using Eqs. (1) to (5) [3, 4].
Variance = S2 = ̅ ̅ ̅
(1) The variances calculated for each trial are then used in the calculation of a weighted average i.e. pooled variance of the individual variances for each trial.
Pooled variance = = ( ) ( )
(2) Standard deviationpooled = √ (3) [MIN] = t.s √
(4) [MINC] = t.s √
(5) Where, t = appropriate value from “t-table”, s = pooled standard deviation, m = number of plus signs in column, k = number of replicates in each trial, c = number of center point.
The t value of 2.093 is taken from the student‟s “t” table for 95% confidence level and 19 df (resulting from sixteen (16) trials with two replicates and one trial with four replicates as df = 16(2-1)+1(4-1) = 19).
III. RESULTS AND DISCUSSION
The effects of the factors (amount of powder (g), concentration of sulfuric acid (mol/L), volume of sulfuric acid (mL) and Temperature (oC)) on the percentage dissolutions of manganese and zinc have been elucidated by the Yates experimental design (24 factorial design).
A. Modeling of Mn(II) Dissolution by Factorial Experimentation
The factorial experimentations of the leaching of the waste dry cell powder by sulfuric acid solution, containing glucose as reducing agent, have been carried out. This experimentation allows us to model the system in terms of Mn(II) dissolution, for a 5 g sample at a constant leaching time of 1 h and constant pulp agitation speed of 300 rpm. The experimental ranges of variables (factors) considered in this study are listed in Table 1.
As the design used is 4 factor-two level factorial, these are 24 = 16 trials. Each trial is run in duplicate yielding 32 trials. In order to check the lack of fit due to curvature, additional trials are made at the mid-point level of each factor.
Table 2 illustrates the two-level, four-factor design with factors in coded form. The experimental runs for trial 1 through 16 are run in duplicate and the trial 17 is run four times.
TABLE I. PROCESS VARIABLES AND RESPONSE FOR LEACHING OF 5 G SAMPLE AT LEACHING TIME OF 1 H AND STIRRING SPEED OF 300 RPM.
Factor Level
(+) (0) (-)
(a) Glucose, g 5.00 2.75 0.50
(b) [H2SO4], mol/L 2.00 1.25 0.50
(c) Vol. of H2SO4, mL 250.0 137.50 25.00
(d) Temp., oC 100.00 75.00 50.00
Response: Y (yield) = % dissolution of either Mn(II) or Zn(II)
The results of the experiments are also given in Table 2 (6th to 9th columns). The average yield, ( ̅), variance (Sn), pooled variance ( ), minimum significant factor effect ([MIN]), degree of freedom (df) and minimum curvature effect ([MINC]) are calculated as usual [2-4]. The values of [MIN]
and [MINC] are calculated to be 0.68 and 1.34, respectively.
The computation analysis is shown in Table 3. The design matrix is supplemented with a computation matrix (to detect interaction effect). The computation matrix is generated by simple algebraic multiplication of the coded factor levels.
The bottom row represents the average yield (% Mn(II) dissolution) for each trial. The sum +‟s column is generated by totaling the response values on each column with a plus for each row. The sum -‟s column is generated in an analogous way.
The sum of these two columns represents the difference between the responses in the 8 trials, when the factor is at high level, and the responses in the 8 trials when the factor is at a low level. Finally, the effect is calculated by dividing the difference by the number of plus signs in the row.
Since the minimum significant figure, [MIN] is 0.68; all effects excepting ab, bcd and abcd are significant.
Consequently, the results can be expressed as a mathematical model, using a first order polynomial. The values of the coefficients are taken as ½ of the effects since these are based upon coded levels +1 and -1 which are differed by two units.
Y = 58.57 - 4.92 a + 5.42 b + 15.24 c + 5.86 d - 2.09 ac - 1.96 ad + 1.17 bc + 0.68 bd + 1.78 cd - 0.5 abc - 0.36 abd - 0.98 acd (6) In the above equation, factors are expressed in coded units.
These are converted into real units by substituting [coded unit
= {(Real unit – („+‟ levels value + „-‟ levels value)}/{(„+‟
levels value – „-‟levels value)/2}]: a = 0.444 G – 1.222, b = 1.333 S – 1.667, c = 0.0089 V – 1.222 and d = 0.04 T – 3 (where, G = amount of glucose in g; S = strength of sulfuric acid in mol/L; V = volume of H2SO4 solution in mL; and T = temperature in oC] in the above equation. This allows us to derive a model for manganese dissolution as:
Y = 29.16 - 1.28 G - 0.135 S + 0.053 V + 0.11 T + 0.994 GS + 0.0066 GV - 0.003 GT + 0.021 SV + 0.06 ST + 0.0011 VT - 0.0026 GSV - 0.0086 GST - 0.00016 GVT (7) B. Modeling of Zn(II) Dissolution by Factorial
Experimentation
To model the system in terms of Zn(II) dissolution, for 5 g sample at constant leaching time of 1 h and constant pulp International Conference on Materials, Electronics & Information Engineering, ICMEIE-2015
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ISBN 978-984-33-8940-4
TABLE II. EXPERIMENTAL DESIGN AND RESULTS OF FOUR FACTOR EXPERIMENT ON LEACHING OF 5 G POWDER FOR 1 H AT 300 RPM.
Trial No.
Design Results (% dissolution of Mn(II)) Results (% dissolution of Zn(II))
(a) (b) (c) (d) Yield
Variance Yield
Variance
Y1 Y2 ̅ Y1 Y2 ̅
1. + + + + 78.40 77.40 77.90 0.50 81.20 78.80 80.00 2.88
2. - + + + 100.00 99.40 99.70 0.18 100.00 99.80 99.90 0.02
3. + - + + 65.70 64.50 65.10 0.72 71.00 69.40 70.20 1.28
4. - - + + 82.50 83.70 83.10 0.72 89.00 86.00 87.50 4.50
5. + + - + 47.40 49.00 48.20 1.28 53.60 55.20 54.40 1.28
6. - + - + 55.60 57.00 56.30 0.98 61.20 59.80 60.50 0.98
7. + - - + 39.50 38.50 39.00 0.50 42.60 45.40 44.00 3.92
8. - - - + 45.20 47.00 46.10 1.62 51.60 50.00 50.80 1.28
9. + + + - 68.00 66.80 67.40 0.72 70.80 73.20 72.00 2.88
10. - + + - 77.10 76.10 76.60 0.50 79.80 82.20 81.00 2.88
11. + - + - 57.40 56.20 56.80 0.72 60.00 60.60 60.30 0.18
12. - - + - 63.30 64.50 63.90 0.72 68.50 67.10 67.80 0.98
13. + + - - 41.40 42.20 41.80 0.32 46.00 45.00 45.50 0.50
14. - + - - 43.60 44.40 44.00 0.32 49.00 48.80 48.90 0.02
15. + - - - 33.60 32.40 33.00 0.72 38.00 36.80 37.40 0.72
16. - - - - 38.70 37.70 38.20 0.50 41.80 43.20 42.50 0.98
17. 0 0 0 0 61.00 64.20
62.40 1.820 62.80 63.20
64.20 2.19
62.50 61.90 64.80 66.00
TABLE III. DESIGN AND COMPUTATION MATRIX FOR 4-FACTOR EXPERIMENTS IN MN(II) AND ZN(II) DISSOLUTION FROM WASTE DRY CELL POWDER.AN ALIQUOT OF 5 G SAMPLE BEING LEACHED FOR 1 H AT 300 RPM.
Trial
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Mean + + + + + + + + + + + + + + + +
Design Matrix
A + - + - + - + - + - + - + - + -
B + + - - + + - - + + - - + + - -
C + + + + - - - - + + + + - - - -
d + + + + + + + + - - - - - - - -
Computation Matrix
ab + - - + + - - + + - - + + - - +
ac + - + - - + - + + - + - - + - +
ad + - + - + - + - - + - + - + - +
bc + + - - - - + + + + - - - - + +
bd + + - - + + - - - - + + - - + +
cd + + + + - - - - - - - - + + + +
abc + - - + - + + - + - - + - + + -
abd + - - + + - - + - + + - - + + -
acd + - + - - + - + - + - + + - + -
bcd + + - - - - + + - - + + + + - -
abcd + - - + - + + - - + + - + - - +
f̅ Mn2+ 77.90 99.70 65.10 83.10 48.20 36.30 39.00 46.10 67.40 76.60 56.80 63.90 41.80 44.00 33.00 38.20 Zn2+ 80.00 99.90 70.20 87.50 54.40 60.50 44.00 50.80 72.00 81.00 60.30 67.80 45.50 48.90 37.40 42.50
…..Continued horizontally…..
For Mn2+ For Zn2+
Sum +’s Sum –‘s Sum Difference Effect Sum +’s Sum –‘s Sum Difference Effect
Mean 937.10 0.00 937.10 937.10 58.569 1002.70 0.00 1002.70 1002.70 62.67
Design Matrix
a 429.20 507.90 937.10 -78.70 -9.838 463.80 538.90 1002.70 -75.10 -9.39
b 511.90 425.20 937.10 86.70 10.838 542.20 460.50 1002.70 81.70 10.21
c 590.50 346.60 937.10 243.90 30.488 618.70 384.00 1002.70 234.70 29.34
d 515.40 421.70 937.10 93.70 11.713 547.30 455.40 1002.70 91.90 11.49
Computation Matrix
ab 466.60 470.50 937.10 -3.90 -0.488 500.50 502.20 1002.70 -1.70 -0.21
ac 451.80 485.30 937.10 -33.50 -4.188 485.20 517.50 1002.70 -32.30 -4.04
ad 452.90 484.20 937.10 -31.30 -3.913 488.80 513.90 1002.70 -25.10 -3.14
bc 477.90 459.20 937.10 18.70 2.338 507.60 495.10 1002.70 12.50 1.56
bd 474.00 463.10 937.10 10.90 1.363 502.80 499.90 1002.70 2.90 0.36
cd 482.80 454.30 937.10 28.50 3.563 511.90 490.80 1002.70 21.10 2.64
abc 464.60 472.50 937.10 -7.90 -0.988 498.10 504.60 1002.70 -6.50 -0.81
abd 465.70 471.40 937.10 -5.70 -0.712 500.30 502.40 1002.70 -2.10 -0.26
acd 460.70 476.40 937.10 -15.70 -1.963 493.20 509.50 1002.70 -16.30 -2.04
bcd 469.20 467.90 937.10 1.30 0.163 497.20 505.50 1002.70 -8.30 -1.04
abcd 469.70 467.40 937.10 2.30 0.288 501.30 501.40 1002.70 -0.10 -0.01
f= as per design matrix International Conference on Materials, Electronics & Information Engineering, ICMEIE-2015
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TABLE IV.DATA FOR COMPARISON OF MODEL VALUE WITH THE EXPERIMENTAL VALUE AND OPTIMIZATION OF FACTORS. Glucose,
g
[H2SO4], mol/L
Vol. of H2SO4, mL
Temp.,
oC
% dissolution Mn(II) % dissolution Zn(II)
Exp. Cal. Deviation Exp. Cal. Deviation
1.00 2.00 250 100 98.00 98.18 -0.18 96.88 96.79 0.09
1.50 2.00 250 100 95.25 95.70 -0.45 94.52 94.73 -0.21
2.50 2.00 250 100 90.55 90.74 -0.19 91.08 90.60 0.49
5.00 0.70 250 100 67.05 67.24 -0.19 70.55 70.98 -0.43
5.00 1.00 250 100 70.01 69.80 0.21 72.99 73.12 -0.13
5.00 1.80 250 100 76.22 76.62 -0.40 78.55 78.84 -0.29
0.50 2.00 50 100 61.01 61.12 -0.11 65.00 65.06 -0.06
0.50 2.00 100 100 70.91 71.00 -0.09 73.15 73.51 -0.36
0.50 2.00 150 100 80.46 80.89 -0.43 81.82 81.96 -0.14
0.50 2.00 250 100 99.70* 100.66 -0.96 99.90* 98.86 1.05
0.50 2.00 100 35 50.15 50.08 0.07 55.95 56.14 -0.19
0.50 2.00 100 55 56.22 56.52 -0.30 61.25 61.48 -0.23
0.50 2.00 100 75 62.65 62.96 -0.31 66.91 66.83 0.08
*Average of 5 experimental values with variation within ±0.45% for Mn(II) and ±0.60% for Zn(II).
agitation speed of 300 rpm, the experimental ranges of variables (factors) considered in this study are identical to those used for Mn(II), as listed in Table 1. The two-level four- factor design with factors in coded form (2nd to 5th columns) and the results of the experiments (10th to 13th columns) are shown in Table 2.
The average yield, ( ̅), variance (Sn), pooled variance ( ), minimum significant factor effect ([MIN]), degree of freedom (df) and minimum curvature effect ([MINC]) are calculated as usual and as in the case of Mn(II) in this study.
The values of [MIN] and [MINC] are calculated to be 0.943 and 1.886, respectively.
Subsequent treatments are done as usual. Since the minimum significant figure, [MIN] is 0.943; all effects excepting ab, bd, abc, abd and abcd are found to be significant. Consequently, the results can be expressed as a mathematical model using a first order polynomial as follows:
Y = 62.67 - 4.694 a + 5.106 b + 14.67 c + 5.744 d - 2.02 ac - 1.57 ad + 0.78 bc + 1.32 cd -1.02 acd - 0.52 bcd (8) On converting coded units by real units, one gets the model for zinc dissolution as:
Y = 30.37 – 0.56 G + 3.0 S + 0.049 V + 0.14 T + 0.004 GV - 0.0057 GT + 0.028 SV + 0.034 ST + 0.0012 VT - 0.0016 GVT - 0.00025 SVT (9) in which G, S, V and T stand for amount of glucose (g), strength of acid (mol/L), volume of acid (mL) and temperature (oC), respectively.
C. Comparison of model value with the experimental value and optimization of factors
Table 4 compares model values with experimental values, obtained at different combinations of factors for both cases.
The deviations are within ±1%.
The optimized factors (i.e experimental parameters) for almost 100% dissolutions of both metals, from 5 g powder, are found to be 0.5 g glucose and 250 mL of 2 mol/L sulfuric acid at 100oC, with a leaching time of 1 h and at stirring speed 300 rpm. The leached solution is found to contain: (7.08±0.10) g/L
Mn(II), (2.20±0.06) Zn(II), ~0.40 g/L Fe(III) and traces of other metals.
IV. CONCLUSIONS
The factor and interaction effects in leaching have been determined by 24 factorial designs for both Mn and Zn dissolutions at leaching time of 1 h and pulp agitation of 300 rpm. The equations for the dissolutions are:
Y = 29.16 - 1.28G - 0.135S + 0.053V + 0.11T + 0.994GS + 0.0066GV - 0.003GT + 0.021SV + 0.06ST + 0.0011VT - 0.0026GSV - 0.0086GST - 0.00016GVT; and
Y = 30.37 – 0.56G + 3.0S + 0.049V + 0.14T + 0.004GV - 0.0057GT + 0.028SV + 0.034ST + 0.0012VT - 0.0016GVT - 0.00025SVT
for Mn(II) and Zn(II), respectively. In these equations, G = amount of glucose (g), S = strength of acid (mol/L), V = volume of acid (mL) and T = temperature (oC). Leaching of 5 g powder at optimized condition i.e. by 250 mL 2 mol/L sulfuric acid solution containing 0.5 g glucose at 100oC and 300 rpm for 1 h, resulted in a solution containing (7.08±0.10) g/L Mn(II), (2.20±0.06) Zn(II) and ~0.40 g/L Fe(III), corresponding to 99.7% and 99.9% dissolutions of Mn(II) and Zn(II), respectively.
REFERENCES
[1] R.K. Biswas, A.K. Karmakar, and M.N. Hossain, "Recovery of manganese and zinc from waste dry cell powder: Part I:
Characterization and Leaching," this proceeding.
[2] R.K. Biswas and A.K. Karmakar, "Solvent extraction of Ti(IV) in the Ti(IV)–SO42− (H+, Na+) – Cyanex 302–kerosene–5% (v/v) hexan-1-ol system," Hydrometallurgy, vol. 134-135, pp. 1-10, 2013.
[3] O.L. Davies, Design and Analysis of Industrial Experiments.
London: Longman, 1979, p. 636.
[4] M. Saha, S.T.A. Islam, D. Saha, M. Ismail, M. Galib, and N.
Sharif, "Application of Statistical Experimental Design to Benzylation of p-Chlorophenol," Bangladesh J. Sci. Ind. Res., vol.
45, pp. 105-110, 2010.
[5] J. Bassett, R.C. Denney, G.H. Jeffery, and J. Mandham, "Vogel's text book of inorganic quantitative analysis," 3rd ed London:
ELBS and Longman, 1978, pp. (a) 330, (b) 746.
International Conference on Materials, Electronics & Information Engineering, ICMEIE-2015 05-06 June, 2015, Faculty of Engineering, University of Rajshahi, Bangladesh
www.ru.ac.bd/icmeie2015/proceedings/
ISBN 978-984-33-8940-4
