Abstract
Crystal joints and faces in non-activated boehmite and, state of agglomeration of particles, degree of amorphization, microcrystallite dimension and, strain in mechanically activated boehmite are indicators of structural heterogeneity which influences reactivity of the solid phase. The focus of this paper is on understanding the manifestation of the heterogeneity during alkali leaching of a boehmite (specific surface area—263 m2/g), without and with mechanical activation using planetary milling up to 240 minutes. A two-prong strategy is used for this purpose which involved analysis of the kinetics of leaching by a model-free approach using ‘isoconversional method’ and, in parallel, characterization of the reacting solid after different durations of leaching. Unlike model-fitting methods, the kinetic analysis revealed sample-dependent variation of apparent activation energy with fraction leached. Changes observed in the morphology of samples (by SEM), particle size distribution (by laser diffraction), and crystalline nature (by powder X-ray diffraction) are used to explain activation energy changes and propose mechanisms of leaching. The effect of mechanical activation on rate constant is assessed and it has been found that up to ~23-fold increase in rate is possible depending on the activation time, leaching temperature, and fraction leached. Further, based on binary correlations between activation energy at different fractions leached and initial characteristics of the samples, it is found that the leaching is predominantly influenced by structural changes during milling, namely, degree of amorphization, microcrystallite dimension, and strain, vis-à-vis specific surface area. Significantly, the paper highlights limitation of model-fitting methods used by most researchers to analyze the kinetics of leaching, especially for mechanically activated minerals.
Similar content being viewed by others
Abbreviations
- α :
-
Fraction leached
- a, b, c :
-
Lattice parameters (nm)
- a/c :
-
Alkali to caustic weight ratio
- A m :
-
Degree of amorphization (pct)
- d 10, d 50, d 90 :
-
Characteristic particle diameters (µm)
- ε :
-
Microstrain
- E a :
-
Activation energy (kJ/mol)
- E aα , E *aα :
-
α dependent E a (kJ/mol)
- ΔE *aα :
-
Stored energy E aα − E *aα (kJ/mol)
- g(α):
-
Functional form of integrated reaction model
- k/k* :
-
Rate constant ratio
- MCD:
-
Microcrystallite size (nm)
- R :
-
Gas constant
- R 2 :
-
Correlation coefficient
- r xy :
-
Binary correlation coefficient
- SSAGeo :
-
Geometrical specific surface area (m2/g)
- SSABET :
-
BET specific surface area (m2/g)
- t MA :
-
Milling or mechanical activation time (min)
- t :
-
Leaching or reaction time (min)
- t α :
-
Leaching time for fraction leached α (min)
- T :
-
Temperature (K)
- Z,Z* :
-
Pre-exponential factor
References
C. Marquez-Alvarez, N. Zilkova, J. Perez-Pariente and J. Cejka : Catalysis Reviews, 2008, vol. 50, pp. 222-286.
T.C. Alex, Rakesh Kumar, S.K. Roy and S.P. Mehrotra: in Light Metals 2012, C.E. Suarez, ed., The Minerals, Metals & Materials Society (TMS), Warrendale, PA, 2012, pp. 15–19.
J.J. Kotte: in Light Metals 1981, P.G. Campbell, ed., The Minerals, Metals & Materials Society (TMS), Warrendale, PA, 1981, pp. 46–81.
R.A. Peterson, G.J. Lumetta, B.M. Rapko and A.P. Poloski, Sep. Sci. Technol., 2007, vol. 42, pp. 1719-1730.
A.S. Russell, J.D. Edwards and C.S. Taylor, Journal of Metals, 1955, vol. 203, pp. 1123-1128.
R.F. Scotford and J.R. Glastonbury, Can. J. Chem. Eng., 1971, vol. 49, 611-616.
R.F. Scotford and J.R. Glastonbury, Can. J. Chem. Eng., 1972, vol. 50, 754-758.
A. Packter and H.S. Dhillon, Z. Phys. Chem., 1975, vol. 256, pp. 801-807.
A. Packter, Colloid Polym. Sci., 1976, vol. 254, 1024–1029.
T. Ejima, K. Shimakage and K. Agatsuma, Journal of Japan Institute of Light Metals, 1980, vol. 30(2), pp. 98-105 (in Japanese with English abstract).
N.S. Maltz, V.M. Sizyakov and N.S. Shmorgunenko: in Light Metals 1983, E.M. Adkins, ed., The Minerals, Metals & Materials Society (TMS), Warrendale, PA, 1983, pp. 99–107.
D. Panias, P. Asimidis and I. Paspaliaris, Hydrometallurgy, 2001, vol. 59, pp. 15-29.
R.L. Russell and R.A. Peterson, Ind. Eng. Chem. Res., 2010, vol. 49, pp. 4542-4545.
H. Grénman, T. Salmi, D.Y. Murzin and J. Addai-Mensah, Hydrometallurgy, 2010, vol. 102, pp. 22-30.
I. Djuric, I. Mihajlovic, Z. Zivkovic and R. Filipović, Chem. Eng. Comm., 2010, vol. 197, 1485.
I. Djuric, I. Mihajlovic and Z. Zivkovic, Can. Metall. Q, 2010, vol. 49(3), pp. 209-218.
B. Li, Z. Ting-an, D. Zhi-he, L. Guo-zhi, G. Yong-nan, N. Pei-yuan, W. Xu-jian and M. Jia, T. Nonferr. Metal. Soc., 2011, vol. 21, pp. 173-178.
T.C. Alex, Rakesh Kumar, S.K. Roy and S.P. Mehrotra, Powder Technol., 2011, vol. 208, pp. 128-136.
T.C. Alex, Rakesh Kumar, S.K. Roy and S.P. Mehrotra, Hydrometallurgy, 2013, vol. 137, pp. 23-32.
W.H. Casey and B. Bunker, Reviews in Mineralogy and Geochemistry, 1990, vol. 23(1), pp. 397-426.
A.P. Prosser, Hydrometallurgy, 1996, vol. 41(2-3), pp. 119-153.
Z. Juhasz and L. Opoczky, Mechanical Activation of Minerals by Grinding: Pulverizing and Morphology of Particles, Akademiai kiado, Budapest, 1990.
P. Baláž, M. Achimovičová, M. Baláž, P. Billik, Z. Cherkezova-Zheleva, J.M. Criado, F. Delogu, E. Dutková, E. Gaffet, F.J. Gotor, Rakesh Kumar, I. Mitov, T. Rojac, M. Senna, A. Streletskii and K. Wieczorek-Ciurowa, Chem. Soc. Rev., 2013, vol. 42, pp. 7571-7637.
F. Pawlek, M.J. Kheiri, and R. Kammel: in Light Metals 1992, E.R. Cutshall, ed., The Minerals, Metals and Materials Society (TMS), Warrendale, PA, 1992, pp. 91–95.
P. G. McCormick, T. Picaro and P.A.I. Smith, Miner. Eng., 2002, vol. 15, pp. 211-214.
T.C. Rakesh Kumar, M.K. Alex, Z.H. Jha, S.P. Khan, S.P. Mahapatra, and C.R. Mishra : in Light Metals 2004, P. Crepeau, ed., The Minerals, Metals & Materials Society, Warrendale, PA, pp. 31–34.
T.C. Rakesh Kumar, Z.H. Alex, S.P. Khan, Mahapatra, and S.P. Mehrotra: in Light Metals 2005, H. Kvande, ed., The Minerals, Metals & Materials Society, Warrendale, PA, 2005, pp. 77–79.
S. Fortin and G. Forté: in Light Metals 2007, M. Sorlie, ed., The Minerals, Metals & Materials Society, Warrendale, PA, 2007, pp. 87–92.
E. Taskin, K. Yidiz and A. Alp: Miner. Metall. Process., 2009, vol. 26(4), pp. 222-225.
G. Greifzu: Diploma Thesis, Institute of Nonferrous Metallurgy and Purest Materials, TU Freiberg, 2012.
T.C. Alex, Rakesh Kumar, S.K. Roy and S.P. Mehrotra, Hydrometallurgy, 2014, vol. 144-145, 99-106.
V. K. Smolyakov, O. V. Lapshin and V. V. Boldyrev, Theor. Found. Chem. Eng., 2008, vol. 42(1), pp. 54-59.
E. V. Bogatyreva, A. G. Ermilov and K. V. Podshibyakina, Inorg. Mater., 2009, vol. 5(12), pp. 1375-1381.
N.J. Welham and D.J. Llewellyn, Miner. Eng., 1998, vol. 11, 827-841.
A.M. Kalinkin and E.V. Kalinkina, Hydrometallurgy, 2011, vol. 108, pp. 189-194.
S. Vyazovkin, Thermochim Acta, 2000, vol. 355, p. 155-163.
A. Khawam and D.R. Flanagan, Thermochim. Acta, 2005, vol. 429, pp. 93-102.
A. Khawam and D.R. Flanagan, J. Pharm. Sci., 2006, vol. 95(3), 472-498.
A.I. Vogel: Vogel’s Textbook of Quantitative Chemical Analysis, 5th ed. (revised by G. H. Jeffery et al.), Longman Group U.K. Limited, 1989.
M. Kitamura and M. Senna, Adv. Powder Technol., 2001, vol. 12(2), pp. 215-226.
D. Panias and I. Paspaliaris, ERZMETALL, 1999, vol. 52(11), pp. 585-595.
W. Chesworth, Clay Clay Miner., 1972, vol. 20, pp. 369-374.
K. Wefers, Metall, 1967, vol. 25(5), pp. 422-431.
K. Wefers and C. Misra: Oxides and Hydroxides of Aluminum, Alcoa Technical Paper No. 19, Revised, Alcoa Laboratories, 1987.
J.A. Apps, J.M. Neil, and C. Jun: “Thermochemical Properties of Gibbsite, Bayerite, Boehmite, Diaspore and the Aluminate ion Between 273 K and 623 K (0 °C and 350 °C)”, Report No. LBL-21482, US Department of Energy, August 1988.
P. Baláž, Extractive Metallurgy of Activated Minerals, Elsevier, Amsterdam, 2000.
A.N. Zelikman, G.M. Voldman and L.V. Beljajevskaja, Theory of Hydrometallurgical Processes, Metallurgija, Moscow 1975 (in Russian) (cited in Reference 46).
P. Baláž, Mechanochemistry in Nanoscience and Minerals Engineering, Springer-Verlag, Heidelberg/Berlin, 2008.
J.J.C. Jansz, Hydrometallurgy, 1984, vol. 12(2), pp. 225-243.
A. Lüttge, R.S. Arvidson and C. Fis, Elements, 2013, vol. 9(3), pp.183-188.
Acknowledgments
The authors acknowledge the constructive criticism of this work and useful suggestions from Prof. S.P Mehrotra (formerly Director CSIR-NML and presently at IIT Gandhinagar, India). This work was carried out as a part of Department of Science and Technology sponsored project (ILTP/A-2.55).
Author information
Authors and Affiliations
Corresponding author
Additional information
Manuscript submitted August 13, 2014.
Rights and permissions
About this article
Cite this article
Kumar, R., Alex, T.C. Elucidation of the Nature of Structural Heterogeneity During Alkali Leaching of Non-activated and Mechanically Activated Boehmite (γ-AlOOH). Metall Mater Trans B 46, 1684–1701 (2015). https://doi.org/10.1007/s11663-015-0343-9
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11663-015-0343-9