Journal of Sustainable Metallurgy

, Volume 5, Issue 1, pp 1–8 | Cite as

Searching for Acidity or the Case of the Missing Chlorine: An Option for a Global Closed Loop Alkalinity–Acidity Cycle for Bauxite Residue Neutralization Based on HCl from PVC Recycling

  • Marcel SchlafEmail author
Research Article


The Bayer process depends on the large-scale use of caustic soda (NaOH)—produced at > 60 million tons/year from NaCl by the chlor-alkali process—and is thus one of the major consumers of the alkalinity generated by the latter. A part of this alkalinity then ultimately ends up in the bauxite residue from the Bayer process, arguably constituting one of the main chemical, technical, and environmental challenges for a valorization or long-term safe disposal and remediation of this material. By stoichiometric and chemical necessity, the complementary acidity resides in the Cl2 gas is also produced in the chlor-alkali process and is thus latent in the chlorinated compounds—notably polyvinyl chloride (PVC) and chlorinated solvents, such as dichloromethane or 1,1,1,-trichloroethane. Recapturing and recycling Cl2 from these uses in the form of hydrochloric acid (HCl) by means of a controlled thermal decomposition of the chlorinated hydrocarbons could—in principle—serve as a source of Brønsted acidity for the neutralization of bauxite residue (Red Mud) thereby transforming it into a nonhazardous material of much lower environmental concern limited to its NaCl content. This could establish a closed alkalinity–acidity cycle on a global scale while simultaneously addressing the end-of-life fate of environmentally persistent PVC that otherwise either is deposited in landfills or can end up in the oceans in form of dispersed microplastics.


Bauxite residue Polyvinylchloride (PVC) Neutralization Recycling Synergistic co-processing 



The author thanks Dr. Jenny Cox (at the Dept. of Chem., Univ. of Guelph) for helpful suggestions.

Compliance with Ethical Standards

Conflict of interest

The author declares no Conflict of Interest with any of the stake holders and industries mentioned in this article.


  1. 1.
    Gräfe M, Power G, Klauber C (2011) Bauxite residue issues: III. Alkalinity and associated chemistry. Hydrometallurgy 108:60–79CrossRefGoogle Scholar
  2. 2.
    Gräfe M, Klauber C (2011) Bauxite residue issues: IV. Old obstacles and new pathways for in situ residue bioremediation. Hydrometallurgy 108:46–59CrossRefGoogle Scholar
  3. 3.
    Dean JA (1992) Lange’s handbook of chemistry. McGraw-Hill, TorontoGoogle Scholar
  4. 4.
    Khaitan S, Dzombak David A, Lowry Gregory V (2009) Mechanisms of neutralization of bauxite residue by carbon dioxide. J Environ Eng 135:433–438CrossRefGoogle Scholar
  5. 5.
    Bridgwater AV (2012) Review of fast pyrolysis of biomass and product upgrading. Biomass Bioenergy 38:68–94CrossRefGoogle Scholar
  6. 6.
    Zhang Q, Chang J, Wang TJ, Xu Y (2007) Review of biomass pyrolysis oil properties and upgrading research. Energy Convers Manag 48:87–92CrossRefGoogle Scholar
  7. 7.
    Mohan D, Pittman CU, Steele PH (2006) Pyrolysis of wood/biomass for bio-oil: a critical review. Energy Fuels 20:848–889CrossRefGoogle Scholar
  8. 8.
    Jollet V, Gissane C, Schlaf M (2014) Optimization of the neutralization of Red Mud by pyrolysis bio-oil using a design of experiments approach. Energy Environ Sci 7:1125–1133CrossRefGoogle Scholar
  9. 9.
    Patel M, Zhang XL, Kumar A (2016) Techno-economic and life cycle assessment on lignocellulosic biomass thermochemical conversion technologies: a review. Renew Sustain Energy Rev 53:1486–1499CrossRefGoogle Scholar
  10. 10.
    Mirkouei A, Haapala KR, Sessions J, Murthy GS (2017) A review and future directions in techno-economic modeling and optimization of upstream forest biomass to bio-oil supply chains. Renew Sustain Energy Rev 67:15–35CrossRefGoogle Scholar
  11. 11.
    Bray AW, Stewart DI, Courtney R, Rout SP, Humphreys PN, Mayes WM, Burke IT (2018) Sustained bauxite residue rehabilitation with gypsum and organic matter 16 years after initial treatment. Environ Sci Technol 52:152–161CrossRefGoogle Scholar
  12. 12.
    Higgins D, Curtin T, Courtney R (2017) Effectiveness of a constructed wetland for treating alkaline bauxite residue leachate: a 1-year field study. Environ Sci Pollut Res 24:8516–8524CrossRefGoogle Scholar
  13. 13.
    Santini TC, Peng YG (2017) Microbial fermentation of organic carbon substrates drives rapid pH neutralization and element removal in bauxite residue leachate. Environ Sci Technol 51:12592–12601CrossRefGoogle Scholar
  14. 14.
    Santini TC, Malcolm LI, Tyson GW, Warren LA (2016) pH and organic carbon dose rates control microbially driven bioremediation efficacy in alkaline bauxite residue. Environ Sci Technol 50:11164–11173CrossRefGoogle Scholar
  15. 15.
    Schmittinger P, Florkiewicz T, Curlin LC, Lüke B, Scannell R, Navin T, Zelfel E, Bartsch R (2000) in “Chlorine”; Ullmann’s encyclopedia of industrial chemistry. Wiley-VCH Verlag GmbH & Co, KGaAGoogle Scholar
  16. 16.
    Kurt C, Bittner J (2000) in “Sodium Hydroxide”; Ullmann’s encyclopedia of industrial chemistry. Wiley-VCH Verlag GmbH & Co, KGaAGoogle Scholar
  17. 17.
    Trummal A, Lipping L, Kaljurand I, Koppel IA, Leito I (2016) Acidity of strong acids in water and dimethyl sulfoxide. J Phys Chem A 120:3663–3669CrossRefGoogle Scholar
  18. 18.
    Fischer I, Schmitt WF, Porth H-C, Allsopp MW, Vianello G (2000) in “Poly(Vinyl Chloride)”; Ullmann’s encyclopedia of industrial chemistry. Wiley-VCH Verlag GmbH & Co, KGaAGoogle Scholar
  19. 19.
    Dreher E-L, Beutel KK, Myers JD, Lübbe T, Krieger S, Pottenger LH (2000) in “Chloroethanes and Chloroethylenes”; Ullmann’s encyclopedia of industrial chemistry. Wiley-VCH Verlag GmbH & Co, KGaAGoogle Scholar
  20. 20.
    Rossberg M, Lendle W, Pfleiderer G, Tögel A, Torkelson TR, Beutel KK (2000) in “Chloromethanes”; Ullmann’s encyclopedia of industrial chemistry. Wiley-VCH Verlag GmbH & Co, KGaAGoogle Scholar
  21. 21.
  22. 22.
    Excluding, of course the still unknown and difficult to assess long-term ecological effects of this material when considered under a “true cost accounting” approachGoogle Scholar
  23. 23.
    Halden RU (2010) Plastics and health risks. Annu Rev Public Health 31:179–194CrossRefGoogle Scholar
  24. 24.
    Omara MM (1977) Combustion of PVC. Pure Appl Chem 49:649–660CrossRefGoogle Scholar
  25. 25.
    Agency USEP (2014) Facts an figures about materials, waste and recycling—advancing sustainable materials management: facts and figures report.; (
  26. 26.
    Ordonez S, Sastre H, Diez FV (2001) Characterisation and deactivation studies of sulfided red mud used as catalyst for the hydrodechlorination of tetrachloroethylene. Appl Catal B 29:263–273CrossRefGoogle Scholar
  27. 27.
    Ordonez S, Sastre H, Diez FV (2001) Catalytic hydrodechlorination of tetrachloroethylene over red mud. J Hazard Mater 81:103–114CrossRefGoogle Scholar
  28. 28.
    Ordonez S, Sastre H, Diez FV (2001) Hydrodechlorination of tetrachloroethylene over modified red mud: deactivation studies and kinetics. Appl Catal B 34:213–226CrossRefGoogle Scholar
  29. 29.
    Environex (2017) PVC and fire.
  30. 30.
  31. 31.
    Cains PW, McCausland LJ, Fernandes AR, Dyke P (1997) Polychlorinated dibenzo-p-dioxins and dibenzofurans formation in incineration: effects of fly ash and carbon source. Environ Sci Technol 31:776–785CrossRefGoogle Scholar
  32. 32.
    Elomaa M, Sarvaranta L, Mikkola E, Kallonen R, Zitting A, Zevenhoven CAP, Hupa M (1997) Combustion of polymeric materials. Crit Rev Anal Chem 27:137–197CrossRefGoogle Scholar
  33. 33.
    Yasuhara A, Katami T, Okuda T, Ohno N, Shibamoto T (2001) Formation of dioxins during the combustion of newspapers in the presence of sodium chloride and poly(vinyl chloride). Environ Sci Technol 35:1373–1378CrossRefGoogle Scholar
  34. 34.
    Aracil I, Font R, Conesa JA (2005) Thermo-oxidative decomposition of polyvinyl chloride. J Anal Appl Pyrolysis 74:215–223CrossRefGoogle Scholar
  35. 35.
    Zhang MM, Buekens A, Jiang XG, Li XD (2015) Dioxins and polyvinylchloride in combustion and fires. Waste Manag Res 33:630–643CrossRefGoogle Scholar
  36. 36.
    Carty P, Metcalfe E, White S (1992) A review of the role of iron containing compounds in char forming smoke suppressing reactions during the thermal-decomposition of semirigid poly(vinyl chloride) formulations. Polymer 33:2704–2708CrossRefGoogle Scholar
  37. 37.
    Saeed L, Tohka A, Zevenhoven R, Haapala M (2005) Two-stage combustion of PVC-containing wastes with HCl recovery: an experimental assessment. Energy Sources 27:669–686CrossRefGoogle Scholar
  38. 38.
    Andrady AL (2011) Microplastics in the marine environment. Mar Pollut Bull 62:1596–1605CrossRefGoogle Scholar
  39. 39.
    Cole M, Lindeque P, Halsband C, Galloway TS (2011) Microplastics as contaminants in the marine environment: a review. Mar Pollut Bull 62:2588–2597CrossRefGoogle Scholar
  40. 40.
    Gewert B, Plassmann MM, MacLeod M (2015) Pathways for degradation of plastic polymers floating in the marine environment. Environ Sci-Process Impacts 17:1513–1521CrossRefGoogle Scholar
  41. 41.
    O’Connor IA, Golsteijn L, Hendriks AJ (2016) Review of the partitioning of chemicals into different plastics: consequences for the risk assessment of marine plastic debris. Mar Pollut Bull 113:17–24CrossRefGoogle Scholar
  42. 42.
    Andrady AL (2017) The plastic in microplastics: a review. Mar Pollut Bull 119:12–22CrossRefGoogle Scholar

Copyright information

© The Minerals, Metals & Materials Society 2018

Authors and Affiliations

  1. 1.Department of Chemistry, Guelph-Waterloo-Centre for Graduate Work in Chemistry (GWC)2University of GuelphGuelphCanada

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