Design of a Hydrometallurgical Treatment System for Aluminium Waste - PowerPoint PPT Presentation

Design of a Hydrometallurgical Treatment System for Aluminium Waste Thomas J. Robshaw, Keith Bonser, Glyn Coxhill, Dr Robert Dawson & Dr Mark D. Ogden 1

The SNUCER Group SHEFFIELD Dr Mark D. Ogden 2

Ion-Exchange: What We Do Polymer R - A + R - B + Cation-exchange B + A + matrix R + X - Y - R + Y - X - Anion-exchange Metal separation Juice processing Pharmaceutical Gold refining purification Sugar decolourisation Water softening 3

Spent Potlining (SPL) Hall-Héroult electrolytic cell For aluminium production REDOX reactions: Al 2 O 3 , Na 3 AlF 6 , 2Al 2 O 3 + 3C  4Al + AlF 3 3CO 2 Al 2 O 3 + 3C  2Al + 3CO 4

Characteristics of SPL ENORMOUS SAFE Cement-based STORAGE CHALLENGE 1st-cut 2nd-cut Graphite-based ~50% carbon ≤ 10% fluoride ≤ 1% cyanide EXPLOSIVE TOXIC 5

Graphite and Fluorspar 450 400 350 300 Euro tonne-1 250 200 2nd-cut 150 100 50 0 Fluorspar (CaF 2 ) Graphite Global reserves: 310 MT Global reserves: 800 MT 6 “CRITICAL MINERAL”

Hydrometallurgical SPL Treatment Proposed new system for maximum fluoride recovery Leachate Solid/liquid Ion-exchange circuit mixing separation Mixed-cut SPL Inert Caustic Solid/liquid Solid/liquid Grinding and Acid leach carbon/cement screening leach separation separation product Input Solid waste-stream H 2 SO 4 NaOH Liquid waste-stream Process Output 7

SPL Characterisation and Leaching C o n c e n tra tio n in le a c h a te (m g L -1 ) PXRD 4000 350 Intensity (a.u.) 300 spectra Sample A Sample B 3000 250 200 2000 150 100 1000 2000 50 0 0 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 2 theta 1500 2500 15000 Intensity (a.u.) 1000 2000 Sample A Sample B 10000 0.5 M Na 1500 500 0.25 M SO 4 1000 2- 5000 500 NaOH (1M) / H 2 O 2 (3%), 3 hrs pH ~3 0 0 0 H 2 SO 4 (0.5M), 2 hrs 10 30 50 70 10 30 50 70 F - NO 3 - Fe Al Ca Si Combine leachates 2 theta

La-MTS9501 Resin citrate > sulfate > oxalate > iodide > nitrate > cromate > bromide > thiocyanide > chloride > formate > acetate > fmuoride Puromet MTS9501 Bead diameter = 300 µm 9 F F M. Kanesato et al ., Chem. Letters , 1988 , 207.

Uptake Mechanisms F F F + 2+ Al Al Al H H H F F F O O O H H H CaF 2 Na 3 AlF 6 €370 per €750 per Tonne Tonne *Full coordinate spheres not shown for clarity Change of recovery strategy (Na 3 AlF 6 ) ? T.J. Robshaw et al. , Chem. Eng. J ., 2019, 367 , 149.

Proposed Ion-Exchange Circuit Na 3 AlF 6(aq) pH adjust To Fluoride- precipitation pH selective Lead Fluoride stage electrode Breakthrough electrode column -loaded column column Pump La- La- La- MTS9501 MTS9501 MTS9501 SPL leachate Carousel streams NaOH (aq) Pump Pump Fluoride- Defluoridated leachate selective T.J. Robshaw et al. , J. electrode 11 Hazard. Mater ., 2019, 361 , 200.

Dynamic Resin Performance 1,2 Breakthrough (a.u.) 500 1 Fluoride effluent concentration (mg L-1) SPL 0,8 450 Pump leachate 0,6 400 0,4 350 0,2 300 0 20 30 40 50 60 70 80 90 100 110 120 250 Breakthrough (a.u.) 1,5 200 1 150 0,5 100 0 50 q 0 = 37 mg g -1 100 150 200 250 300 350 400 450 500 0 Effluent volume (mL) Fluoride- 0 50 100 150 200 250 300 350 400 450 500 selective Effluent volume (mL) electrode Experimental Dose-Response model 12

Recovery Elution with water 1M NaOH € 1800 € 1600 € Conc. in eluent (mg L-1) 1400 1200 € € Contaminants 1000 € 800 600 € € 400 200 € 0 0 100 200 300 400 500 600 700 Fluoride Aluminium mL eluent 13

Conclusions La-MTS9501 resin is highly suitable for purpose Al in SPL leachate produces synergistic uptake mechanism Recovery of synthetic cryolite may be possible 14

Acknowledgements Dr Mark Ogden & the SNUCER group Dr Robert Dawson & research group Polymer Centre CDT Engineering & Physical Sciences Research Council Bawtry Carbon International Trimet Aluminium Royal Society of Chemistry (Environment Sustainability & Energy Division) You for listening See poster 123 for more fluoride work! Tjrobshaw1@Sheffield.ac.uk 15

Supporting Information Al Metal Productio n 16

Pyrometallurgical SPL Treatment ✦ Produces 2.5 T waste per T SPL processed ✦ In operation today D.G. Brooks et al ., Light Metals , 1992, 17 283-287.

Proposed Leaching Treatment Ground & screened NaOH (aq) SPL HNO 3(aq) Solid/liquid separation Na 3 AlF 6 and Al 2 O 3 solublised Purifjed Solid/liquid graphite separation CaF 2 and NaAl 4 O 17 solublised Caustic leachate Acidic Slurry leachate H 2 O 2 Impello T o IX r circui 18 CN - Leachate mixing? t destruction

Cryolite Precipitation PXRD spectrum of cryolite precipitated from Literature spectrum for comparison leachate before IX treatment 1000 700 900 600 800 500 700 Intensity (a.u.) 400 600 500 300 400 200 300 100 200 100 0 10 20 30 40 50 60 70 80 0 10 20 30 40 50 60 70 80 2 theta 19

XPS Analysis of Resin Beads La environments Al environments O environments NaF solution 5000 5000 4500 4500 4000 (none) 4000 Counts (s-1) Counts (s-1) 3500 3500 3000 3000 2500 2500 2000 1500 2000 542 537 532 527 522 870 860 850 840 830 820 500 7000 3000 Aluminium 6000 2800 Leachate 400 hydroxyfluoride Counts (s-1) Counts (s-1) Counts (s-1) 5000 2600 (AHF) 300 4000 2400 3000 2200 200 2000 2000 100 1000 1800 85 83 81 79 77 75 73 71 69 67 65 542 537 532 527 522 870 860 850 840 830 820 Binding energy (eV) Binding energy (eV) Binding energy (eV) 20 C. Stosiek et al ., Chem. Mater ., 2010, 22 , 2347. S. Selvasekarapandian et al ., Physica B ., 2003, 337 , 52.

Resin Regeneration Study Equilibrium fluoride uptake of La-MTS9501 over 5 adsorption/desorption cycles 70 60 50 40 30 qe (mg g-1) 20 10 0 21