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Gypsum Waste Minimisation

Gypsum Waste Minimisation. Rosemary Greaves Department of Materials Prof. Alan Atkinson Dr. Mark Tyrer. Presented at the 3 rd Annual WARMNET Conference “Tackling Waste 2006”, Nottingham, 6 th and 7 th July 2006. Presentation Outline. The gypsum waste minimisation project

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Gypsum Waste Minimisation

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  1. Gypsum Waste Minimisation Rosemary Greaves Department of Materials Prof. Alan Atkinson Dr. Mark Tyrer Presented at the 3rd Annual WARMNET Conference “Tackling Waste 2006”, Nottingham, 6th and 7th July 2006 © Imperial College London

  2. Presentation Outline • The gypsum waste minimisation project • Titanogypsum by-products • Alternative approaches • The ammonia process • Experimental & analysis • Conclusions & further work © Imperial College London

  3. Gypsum Calcium Sulfate Dihydrate CaSO4.2(H2O) • Vital component of many construction materials • In the UK demand outstrips domestic supply [1] © Imperial College London

  4. Impetus For Work • Sponsors landfill ~75kt of by-product gypsum per annum • Red titanogypsum • Construction site waste • Disposal costs have escalated • EU landfill directive [2] • Increased landfill tax Minimise and reuse gypsum wastes © Imperial College London

  5. Sponsors Huntsman Tioxide Lafarge Plasterboard Funding EPSRC Miniwaste Faraday Partnership Research Partners Imperial College London Professor Alan Atkinson Dr Mark Tyrer Rosemary Greaves Coventry University Dr Peter Claisse Dr Esmaiel Ganjian Seema Karami University of Birmingham Dr Gurmel Ghataora Waliur Rahman The Gypsum Waste Minimisation Project © Imperial College London

  6. Waste Acid Carbon Dioxide Partial Neutralisation Calcium Oxide White Gypsum Complete Neutralisation Calcium Hydroxide Red Gypsum Effluent to Drain Titanogypsum By-products By-product of TiO2 production from ilmenite (FeTiO3) © Imperial College London

  7. Fe(OH)3 Fe(OH)2 Red Titanogypsum Mass per gram (mg/g) Element © Imperial College London

  8. Routes to Red Gypsum Minimisation Precipitate metal salts prior to gypsum formation • Wastewater contains a complex combination of impurities • Focus on colour • Use simplified solution based on sponsor’s analysis © Imperial College London

  9. Pourbaix Diagram [3] Eh (Volts) pH © Imperial College London

  10. Oxidise Eh (Volts) pH © Imperial College London

  11. Increase pH Eh (Volts) pH © Imperial College London

  12. Ammonia Addition Process [4] • Regeneration of NH3 • Iron content 160g/kg 0.42g/kg © Imperial College London

  13. Titration Experiments How does pH effect precipitation? • Produce Analogue: • H2SO4 • FeSO4.7(H2O) • Titrate aqueous ammonia (NH4OH) © Imperial College London

  14. pH 4.7 6.3 6.8 7.0 7.6 8.2 8.7 Precipitation of Iron Samples taken at various pH • Centrifuged • Solids filtered from solution • Iron concentration of solution analysed © Imperial College London

  15. Spectrophotometry • Reduce to iron (II) • Chelate • 1,10-phenanthroline • Illuminate • l=515nm • Visible • monochromatic Intensity a concentration © Imperial College London

  16. Data Analysis © Imperial College London

  17. Effect of pH on Iron Removal © Imperial College London

  18. Conclusions and Future Work • Alkalizing the solution causes iron to precipitate • Concentration of iron decreases with pH • Precipitates must be analysed • Perform a Comparison with alternative techniques • Analyse resultant gypsum samples © Imperial College London

  19. References • Hillier, J. A., L. E. Taylor, et al. (2004). United Kingdom Minerals Yearbook 2004, British Geological Survey. • European Council Directive 1999/31/EC on the Landfill of Waste. 1999. • Roine, A., HSC Chemistry 5.1 for Windows, Outokumpu Research Oy. • Hyvrard, F. and P. Muller, Method for Treating and Upgrading Effluents Containing Metalic Sulphates Using an Ammonia Addition Step. 2004: US. p. 5. © Imperial College London

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