Qiu-song Chen, Shi-yuan Sun, Yi-kai Liu, Chong-chong Qi, Hui-bo Zhou,  and Qin-li Zhang, Immobilization and leaching characteristics of fluoride from phosphogypsum-based cemented paste backfill, Int. J. Miner. Metall. Mater., 28(2021), No. 9, pp. 1440-1452. https://doi.org/10.1007/s12613-021-2274-6
Cite this article as:
Qiu-song Chen, Shi-yuan Sun, Yi-kai Liu, Chong-chong Qi, Hui-bo Zhou,  and Qin-li Zhang, Immobilization and leaching characteristics of fluoride from phosphogypsum-based cemented paste backfill, Int. J. Miner. Metall. Mater., 28(2021), No. 9, pp. 1440-1452. https://doi.org/10.1007/s12613-021-2274-6
Research ArticleCover Article

Immobilization and leaching characteristics of fluoride from phosphogypsum-based cemented paste backfill

+ Author Affiliations
  • Corresponding author:

    Yi-kai Liu    E-mail: yikai.liu@phd.unipd.it

  • Received: 3 February 2021Revised: 25 February 2021Accepted: 26 February 2021Available online: 27 February 2021
  • Phosphogypsum (PG) is a typical by-product of phosphoric acid and phosphate fertilizers during acid digestion. The application of cemented paste backfill (CPB) has been feasibly investigated for the remediation of PG. The present study evaluated fluorine immobilization mechanisms and attempted to construct a related thermodynamic and geochemical modeling to describe the related stabilization performance. Physico-chemical and mineralogical analyses were performed on PG and hardened PG-based CPB (PCPB). The correlated macro- and microstructural properties were obtained from the analysis of the combination of unconfined compressive strength and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy imaging. Acid/base-dependent leaching tests were performed to ascertain fluoride leachability. In addition, Gibbs Energy Minimization Software and PHREEQC were applied as tools to characterize the PCPB hydration and deduce its geochemical characteristics. The results proved that multiple factors are involved in fluorine stabilization, among which the calcium silicate hydrate gel was found to be associated with retention. Although the quantitative comparison with the experimental data shows that further modification should be introduced into the simulation before being used as a predictive implement to determine PG management options, the importance of acid/base concentration in regulating the leaching behavior was confirmed. Moreover, the modeling enabled the identification of the impurity phases controlling the stability and leachability.

  • loading
  • [1]
    Q.S. Chen, Q.L. Zhang, C.C. Qi, A. Fourie, and C.C. Xiao, Recycling phosphogypsum and construction demolition waste for cemented paste backfill and its environmental impact, J. Cleaner Prod., 186(2018), p. 418. doi: 10.1016/j.jclepro.2018.03.131
    [2]
    M. Tsioka and E.A. Voudrias, Comparison of alternative management methods for phosphogypsum waste using life cycle analysis, J. Cleaner Prod., 266(2020), art. No. 121386. doi: 10.1016/j.jclepro.2020.121386
    [3]
    D. Cordell, J.O. Drangert, and S. White, The story of phosphorus: Global food security and food for thought, Glob. Environ. Change, 19(2009), No. 2, p. 292. doi: 10.1016/j.gloenvcha.2008.10.009
    [4]
    J.P. Xu, L.R. Fan, Y.C. Xie, and G. Wu, Recycling-equilibrium strategy for phosphogypsum pollution control in phosphate fertilizer plants, J. Cleaner Prod., 215(2019), p. 175. doi: 10.1016/j.jclepro.2018.12.236
    [5]
    F. Macías, R. Pérez-López, C.R. Cánovas, S. Carrero, and P. Cruz-Hernandez, Environmental assessment and management of phosphogypsum according to European and United States of America regulations, Procedia Earth Planet. Sci., 17(2017), p. 666. doi: 10.1016/j.proeps.2016.12.178
    [6]
    B. Geissler, L. Hermann, M. Mew, and G. Steiner, Striving toward a circular economy for phosphorus: The role of phosphate rock mining, Minerals, 8(2018), No. 9, art. No. 395. doi: 10.3390/min8090395
    [7]
    A.M. Rashad, Phosphogypsum as a construction material, J. Cleaner Prod., 166(2017), p. 732. doi: 10.1016/j.jclepro.2017.08.049
    [8]
    L. Yang, Y.S. Zhang, and Y. Yan, Utilization of original phosphogypsum as raw material for the preparation of self-leveling mortar, J. Cleaner Prod., 127(2016), p. 204. doi: 10.1016/j.jclepro.2016.04.054
    [9]
    M.R. Gorman and D.A. Dzombak, A review of sustainable mining and resource management: Transitioning from the life cycle of the mine to the life cycle of the mineral, Resour. Conserv. Recycl., 137(2018), p. 281. doi: 10.1016/j.resconrec.2018.06.001
    [10]
    E. Saadaoui, N. Ghazel, C. Ben Romdhane, and N. Massoudi, Phosphogypsum: Potential uses and problems—A review, Int. J. Environ. Stud., 74(2017), No. 4, p. 558. doi: 10.1080/00207233.2017.1330582
    [11]
    X.B. Li, J. Du, L. Gao, S.Y. He, L. Gan, C. Sun, and Y. Shi, Immobilization of phosphogypsum for cemented paste backfill and its environmental effect, J. Cleaner Prod., 156(2017), p. 137. doi: 10.1016/j.jclepro.2017.04.046
    [12]
    H. Tayibi, M. Choura, F.A. López, F.J. Alguacil, and A. López-Delgado, Environmental impact and management of phosphogypsum, J. Environ. Manage., 90(2009), No. 8, p. 2377. doi: 10.1016/j.jenvman.2009.03.007
    [13]
    S.H. Yin, Y.J. Shao, A.X. Wu, Z.Y. Wang, and L.H. Yang, Assessment of expansion and strength properties of sulfidic cemented paste backfill cored from deep underground stopes, Constr. Build. Mater., 230(2020), art. No. 116983. doi: 10.1016/j.conbuildmat.2019.116983
    [14]
    H.Y. Cheng, S.C. Wu, X.Q. Zhang, and A.X. Wu, Effect of particle gradation characteristics on yield stress of cemented paste backfill, Int. J. Miner. Metall. Mater., 27(2020), No. 1, p. 10. doi: 10.1007/s12613-019-1865-y
    [15]
    S. Cao, G.L. Xue, E. Yilmaz, and Z.Y. Yin, Assessment of rheological and sedimentation characteristics of fresh cemented tailings backfill slurry, Int. J. Min. Reclam. Environ., 35(2021), No. 5, p. 319. doi: 10.1080/17480930.2020.1826092
    [16]
    Q.S. Chen, Q.L. Zhang, A. Fourie, and C. Xin, Utilization of phosphogypsum and phosphate tailings for cemented paste backfill, J. Environ. Manage., 201(2017), p. 19. doi: 10.1016/j.jenvman.2017.06.027
    [17]
    X.L. Xue, Y.X. Ke, Q. Kang, Q.L. Zhang, C.C. Xiao, F.J. He, and Q. Yu, Cost-effective treatment of hemihydrate phosphogypsum and phosphorous slag as cemented paste backfill material for underground mine, Adv. Mater. Sci. Eng., 2019(2019), art. No. 9087538. doi: 10.1155/2019/9087538
    [18]
    C.D. Min, X.B. Li, S.Y. He, S.T. Zhou, Y.N. Zhou, S. Yang, and Y. Shi, Effect of mixing time on the properties of phosphogypsum-based cemented backfill, Constr. Build. Mater., 210(2019), p. 564. doi: 10.1016/j.conbuildmat.2019.03.187
    [19]
    X.B. Li, S.T. Zhou, Y.N. Zhou, C.D. Min, Z.W. Cao, J. Du, L. Luo, and Y. Shi, Durability evaluation of phosphogypsum-based cemented backfill through drying-wetting cycles, Minerals, 9(2019), No. 5, art. No. 321. doi: 10.3390/min9050321
    [20]
    Y. Huang and Z.S. Lin, Investigation on phosphogypsum-steel slag-granulated blast-furnace slag-limestone cement, Constr. Build. Mater., 24(2010), No. 7, p. 1296. doi: 10.1016/j.conbuildmat.2009.12.006
    [21]
    M. Singh, Effect of phosphatic and fluoride impurities of phosphogypsum on the properties of selenite plaster, Cem. Concr. Res., 33(2003), No. 9, p. 1363. doi: 10.1016/S0008-8846(03)00068-1
    [22]
    W.H. Kang, E.I. Kim, and J.Y. Park, Fluoride removal capacity of cement paste, Desalination, 202(2007), No. 1-3, p. 38. doi: 10.1016/j.desal.2005.12.036
    [23]
    R. Boncukcuoğlu, M.T. Yılmaz, M.M. Kocakerim, and V. Tosunoğlu, Utilization of borogypsum as set retarder in Portland cement production, Cem. Concr. Res., 32(2002), No. 3, p. 471. doi: 10.1016/S0008-8846(01)00711-6
    [24]
    S. Kagne, S. Jagtap, P. Dhawade, S.P. Kamble, S. Devotta, and S.S. Rayalu, Hydrated cement: A promising adsorbent for the removal of fluoride from aqueous solution, J. Hazard. Mater., 154(2008), No. 1-3, p. 88. doi: 10.1016/j.jhazmat.2007.09.111
    [25]
    V. Gopal and K.P. Elango, Equilibrium, kinetic and thermodynamic studies of adsorption of fluoride onto plaster of Paris, J. Hazard. Mater., 141(2007), No. 1, p. 98. doi: 10.1016/j.jhazmat.2006.06.099
    [26]
    B.I. Silveira, A.E.M. Dantas, J.E.M. Blasques, and R.K.P. Santos, Effectiveness of cement-based systems for stabilization and solidification of spent pot liner inorganic fraction, J. Hazard. Mater., 98(2003), No. 1-3, p. 183. doi: 10.1016/S0304-3894(02)00317-5
    [27]
    K. Gijbels, H. Nguyen, P. Kinnunen, P. Samyn, W. Schroeyers, Y. Pontikes, S. Schreurs, and M. Illikainen, Radiological and leaching assessment of an ettringite-based mortar from ladle slag and phosphogypsum, Cem. Concr. Res., 128(2020), art. No. 105954. doi: 10.1016/j.cemconres.2019.105954
    [28]
    M.A. Hwaiti, Influence of treated waste phosphogypsum materials on the properties of ordinary Portland cement, Bangladesh J. Sci. Ind. Res., 50(2015), No. 4, p. 241. doi: 10.3329/bjsir.v50i4.25831
    [29]
    P.E. Tsakiridis, P. Oustadakis, and S. Agatzini-Leonardou, Black dross leached residue: An alternative raw material for Portland cement clinker, Waste Biomass Valorization, 5(2014), No. 6, p. 973. doi: 10.1007/s12649-014-9313-8
    [30]
    G. Dartan, F. Taspinar, and İ. Toroz, Analysis of fluoride pollution from fertilizer industry and phosphogypsum piles in agricultural area, J. Ind. Pollut. Control, 33(2017), No. 1, p. 662.
    [31]
    N. Adimalla, S.K. Marsetty, and P.P. Xu, Assessing groundwater quality and health risks of fluoride pollution in the Shasler Vagu (SV) watershed of Nalgonda, India, Hum. Ecol. Risk Assess., 26(2020), No. 6, p. 1569. doi: 10.1080/10807039.2019.1594154
    [32]
    X.Q. Tang, M. Wu, X.C. Dai, and P.H. Chai, Phosphorus storage dynamics and adsorption characteristics for sediment from a drinking water source reservoir and its relation with sediment compositions, Ecol. Eng., 64(2014), p. 276. doi: 10.1016/j.ecoleng.2014.01.005
    [33]
    M.W. Wang, L. Liu, H.J. Li, Y.G. Li, H.L. Liu, C.C. Hou, Q. Zeng, P. Li, Q. Zhao, L.X. Dong, G.Y. Zhou, X.C. Yu, L. Liu, Q. Guan, S. Zhang, and A.G. Wang, Thyroid function, intelligence, and low-moderate fluoride exposure among Chinese school-age children, Environ. Int., 134(2020), art. No. 105229. doi: 10.1016/j.envint.2019.105229
    [34]
    W.C. Burnett and A.W. Elzerman, Nuclide migration and the environmental radiochemistry of Florida phosphogypsum, J. Environ. Radioact., 54(2001), No. 1, p. 27. doi: 10.1016/S0265-931X(00)00164-8
    [35]
    M. Tafu and T. Chohji, Reaction between calcium phosphate and fluoride in phosphogypsum, J. Eur. Ceram. Soc., 26(2006), No. 4-5, p. 767. doi: 10.1016/j.jeurceramsoc.2005.06.031
    [36]
    H.E. Jamieson, S.R. Walker, and M.B. Parsons, Mineralogical characterization of mine waste, Appl. Geochem., 57(2015), p. 85. doi: 10.1016/j.apgeochem.2014.12.014
    [37]
    X.B. Li, Y.N. Zhou, Q.Q. Zhu, S.T. Zhou, C.D. Min, and Y. Shi, Slurry preparation effects on the cemented phosphogypsum backfill through an orthogonal experiment, Minerals, 9(2019), No. 1, art. No. 31. doi: 10.3390/min9010031
    [38]
    B. Lothenbach, D.A. Kulik, T. Matschei, M. Balonis, L. Baquerizo, B. Dilnesa, G.D. Miron, and R.J. Myers, Cemdata18: A chemical thermodynamic database for hydrated Portland cements and alkali-activated materials, Cem. Concr. Res., 115(2019), p. 472. doi: 10.1016/j.cemconres.2018.04.018
    [39]
    T. Wagner, D.A. Kulik, F.F. Hingerl, and S.V. Dmytrieva, Gem-selektor geochemical modeling package: Tsolmod library and data interface for multicomponent phase models, Can. Mineral., 50(2012), No. 5, p. 1173. doi: 10.3749/canmin.50.5.1173
    [40]
    D.A. Kulik, T. Wagner, S.V. Dmytrieva, G. Kosakowski, F.F. Hingerl, K.V. Chudnenko, and U.R. Berner, GEM-Selektor geochemical modeling package: Revised algorithm and GEMS3K numerical kernel for coupled simulation codes, Comput. Geosci., 17(2013), No. 1, p. 1. doi: 10.1007/s10596-012-9310-6
    [41]
    D.L. Parkhurst and C.A.J. Appelo, Description of input and examples for PHREEQC version 3—A computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations, [in] U.S. Geological Survey Techniques and Methods, book 6, chap. A43, U.S. Geological Survey, Denver, 2013, p. 497.
    [42]
    R.W. Scholz, A.E. Ulrich, M. Eilittä, and A. Roy, Sustainable use of phosphorus: A finite resource, Sci. Total Environ., 461-462(2013), p. 799. doi: 10.1016/j.scitotenv.2013.05.043
    [43]
    Q.S. Chen, Q.L. Zhang, C.C. Xiao, and X. Chen, Backfilling behavior of a mixed aggregate based on construction waste and ultrafine tailings, PLoS One, 12(2017), No. 6, art. No. e0179872. doi: 10.1371/journal.pone.0179872
    [44]
    H.Z. Jiao, S.F. Wang, A.X. Wu, H.M. Shen, and J.D. Wang, Cementitious property of NaAlO2-activated Ge slag as cement supplement, Int. J. Miner. Metall. Mater., 26(2019), No. 12, p. 1594. doi: 10.1007/s12613-019-1901-y
    [45]
    F.B. Chen, B. Xu, H.Z. Jiao, X.M. Chen, Y.L. Shi, J.X. Wang, and Z. Li, Triaxial mechanical properties and microstructure visualization of BFRC, Constr. Build. Mater., 278(2021), art. No. 122275. doi: 10.1016/j.conbuildmat.2021.122275
    [46]
    H.Z. Jiao, Y.C. Wu, W. Wang, X.M. Chen, Y.F. Wang, J.H. Liu, and W.T. Feng, The micro-scale mechanism of metal mine tailings thickening concentration improved by shearing in gravity thickener, J. Renewable Mater., 9(2021), No. 4, p. 637. doi: 10.32604/jrm.2021.014310
    [47]
    Q.S. Chen, Q.L. Zhang, A. Fourie, X. Chen, and C.C. Qi, Experimental investigation on the strength characteristics of cement paste backfill in a similar stope model and its mechanism, Constr. Build. Mater., 154(2017), p. 34. doi: 10.1016/j.conbuildmat.2017.07.142
    [48]
    Y. He, Q.L. Zhang, Q.S. Chen, J.W. Bian, C.C. Qi, Q. Kang, and Y. Feng, Mechanical and environmental characteristics of cemented paste backfill containing lithium slag-blended binder, Constr. Build. Mater., 271(2021), art. No. 121567. doi: 10.1016/j.conbuildmat.2020.121567
    [49]
    Y.X. Yang, T.Q. Zhao, H.Z. Jiao, Y.F. Wang, and H.Y. Li, Potential effect of porosity evolution of cemented paste backfill on selective solidification of heavy metal ions, Int. J. Environ. Res. Public Health, 17(2020), No. 3, art. No. 814. doi: 10.3390/ijerph17030814
    [50]
    E.H. Perkins, Y.K. Kharaka, W.D. Gunter, and J.D. DeBraal, Geochemical modeling of water–rock interactions using SOLMINEQ.88, [in] Chemical Modeling of Aqueous Systems II, American Chemical Society, Washington, p. 117.
    [51]
    J.D. Allison, D.S. Brown, and K.J. Novo-Gradac, Minteqa2/Prodefa2, a Geochemical Assessment Model for Environmental Systems: Version 3.0 Users Manual, Environmental Protection Agency, Athens [2019-10-01]. https://www.osti.gov/biblio/5673069
    [52]
    A.C. Garrabrants, F. Sanchez, and D.S. Kosson, Changes in constituent equilibrium leaching and pore water characteristics of a Portland cement mortar as a result of carbonation, Waste Manage., 24(2004), No. 1, p. 19. doi: 10.1016/S0956-053X(03)00135-1
    [53]
    E. Martens, D. Jacques, V.G. Tom, L. Wang, and D. Mallants, PHREEQC modelling of leaching of major elements and heavy metals from cementitious waste forms, MRS Online Proc. Lib., 1107(2008), art. No. 475. doi: 10.1557/PROC-1107-475
    [54]
    W.A. Sowa, Interpreting mean drop diameters using distribution moments, Atomization Sprays, 2(1992), No. 1, p. 1. doi: 10.1615/AtomizSpr.v2.i1.10
    [55]
    S.F. Lütke, M.L.S. Oliveira, L.F.O. Silva, T.R.S. Cadaval, and G.L. Dotto, Nanominerals assemblages and hazardous elements assessment in phosphogypsum from an abandoned phosphate fertilizer industry, Chemosphere, 256(2020), art. No. 127138. doi: 10.1016/j.chemosphere.2020.127138
    [56]
    C.Y. Jia, L.C. Wu, Q.S. Chen, P. Ke, J.J. De Yoreo, and B.H. Guan, Structural evolution of amorphous calcium sulfate nanoparticles into crystalline gypsum phase, CrystEngComm, 22(2020), No. 41, p. 6805. doi: 10.1039/D0CE01173H
    [57]
    Y. Ennaciri, I. Zdah, H. El Alaoui-Belghiti, and M. Bettach, Characterization and purification of waste phosphogypsum to make it suitable for use in the plaster and the cement industry, Chem. Eng. Commun., 207(2020), No. 3, p. 382. doi: 10.1080/00986445.2019.1599865
    [58]
    Y.B. Jiang, K.D. Kwon, S.F. Wang, C. Ren, and W. Li, Molecular speciation of phosphorus in phosphogypsum waste by solid-state nuclear magnetic resonance spectroscopy, Sci. Total Environ., 696(2019), art. No. 133958. doi: 10.1016/j.scitotenv.2019.133958
    [59]
    B.L″ocsei, Mullite formation in the aluminium fluoride–silica system (AlF3–SiO2), Nature, 190(1961), No. 4779, p. 907. doi: 10.1038/190907a0
    [60]
    V.M. Norwood and J.J. Kohler, Characterization of fluorine-, aluminum-, silicon-, and phosphorus-containing complexes in wet-process phosphoric acid using nuclear magnetic resonance spectroscopy, Fertil. Res., 28(1991), No. 2, p. 221. doi: 10.1007/BF01049754
    [61]
    T. Nishikawa, K. Suzuki, S. Ito, K. Sato, and T. Takebe, Decomposition of synthesized ettringite by carbonation, Cem. Concr. Res., 22(1992), No. 1, p. 6. doi: 10.1016/0008-8846(92)90130-N
    [62]
    T. Grounds, H.G. Midgley, and D.V. Novell, Carbonation of ettringite by atmospheric carbon dioxide, Thermochim. Acta, 135(1988), p. 347. doi: 10.1016/0040-6031(88)87407-0
    [63]
    J.Y. Jiang, Q. Zheng, D.S. Hou, Y.R. Yan, H. Chen, W. She, S.P. Wu, D. Guo, and W. Sun, Calcite crystallization in the cement system: Morphological diversity, growth mechanism and shape evolution, Phys. Chem. Chem. Phys., 20(2018), No. 20, p. 14174. doi: 10.1039/C8CP01979G
    [64]
    B. Šavija and M. Luković, Carbonation of cement paste: Understanding, challenges, and opportunities, Constr. Build. Mater., 117(2016), p. 285. doi: 10.1016/j.conbuildmat.2016.04.138
    [65]
    F.D.C. Holanda, H. Schmidt, and V.A. Quarcioni, Influence of phosphorus from phosphogypsum on the initial hydration of Portland cement in the presence of superplasticizers, Cem. Concr. Compos., 83(2017), p. 384. doi: 10.1016/j.cemconcomp.2017.07.029
    [66]
    M. Bishop, S.G. Bott, and A.R. Barron, A new mechanism for cement hydration inhibition: Solid-state chemistry of calcium nitrilotris(methylene)triphosphonate, Chem. Mater., 15(2003), No. 16, p. 3074. doi: 10.1021/cm0302431
    [67]
    J.Y. Park, H.J. Byun, W.H. Choi, and W.H. Kang, Cement paste column for simultaneous removal of fluoride, phosphate, and nitrate in acidic wastewater, Chemosphere, 70(2008), No. 8, p. 1429. doi: 10.1016/j.chemosphere.2007.09.012
    [68]
    W. Guan and X. Zhao, Fluoride recovery using porous calcium silicate hydrates via spontaneous Ca2+ and OH release, Sep. Purif. Technol., 165(2016), p. 71. doi: 10.1016/j.seppur.2016.03.050
    [69]
    S.V. Tarali, N.P. Hoolikantimath, N. Kulkarni, and P.A. Ghorpade, A novel cement-based technology for the treatment of fluoride ions, SN Appl. Sci., 2(2020), No. 7, art. No. 1205. doi: 10.1007/s42452-020-2986-7
    [70]
    P.A. Ghorpade, M.G. Ha, and J.Y. Park, Effect of different types of calcium sulfate on the reactivity of cement/Fe(II) system in dechlorination of trichloroethylene, Desalin. Water Treat., 54(2015), No. 4-5, p. 1426. doi: 10.1080/19443994.2014.950342
    [71]
    G. Diamantopoulos, M. Katsiotis, M. Fardis, I. Karatasios, S. Alhassan, M. Karagianni, G. Papavassiliou, and J. Hassan, The role of titanium dioxide on the hydration of Portland cement: A combined NMR and ultrasonic study, Molecules, 25(2020), No. 22, art. No. 5364. doi: 10.3390/molecules25225364
    [72]
    B. Lothenbach, L. Pelletier-Chaignat, and F. Winnefeld, Stability in the system CaO–Al2O3–H2O, Cem. Concr. Res., 42(2012), No. 12, p. 1621. doi: 10.1016/j.cemconres.2012.09.002
    [73]
    J.D. Han, G.H. Pan, W. Sun, C.H. Wang, and D. Cui, Application of nanoindentation to investigate chemomechanical properties change of cement paste in the carbonation reaction, Sci. China Technol. Sci., 55(2012), No. 3, p. 616. doi: 10.1007/s11431-011-4571-1
    [74]
    M.A. Peter, A. Muntean, S.A. Meier, and M. Böhm, Competition of several carbonation reactions in concrete: A parametric study, Cem. Concr. Res., 38(2008), No. 12, p. 1385. doi: 10.1016/j.cemconres.2008.09.003
  • 加载中

Catalog

    通讯作者: 陈斌, bchen63@163.com
    • 1. 

      沈阳化工大学材料科学与工程学院 沈阳 110142

    1. 本站搜索
    2. 百度学术搜索
    3. 万方数据库搜索
    4. CNKI搜索

    Figures(9)  / Tables(7)

    Share Article

    Article Metrics

    Article Views(3077) PDF Downloads(177) Cited by()
    Proportional views

    /

    DownLoad:  Full-Size Img  PowerPoint
    Return
    Return