1. Sustainable recycling of a lead battery by directly producing lead grid and value added paste precursor for a new battery R Vasant Kumar Department of Materials Science & Metallurgy University of Cambridge, UK

2. Acknowledgements Seref Sonmez, Vega Kotzeva, Jiakuan Yang, Lilia Sanchez, Richard Darby, Yingjun Liu, David Zou, of Department of Materials Science Lei Wang, Nigel Williams of the Business School Maggie Wilkinson & Zlatka Stoeva of Cambridge Enterprise

3. Lead Battery (> 80 % Lead Usage)

4. Lead Batteries- Leaders in Recycling Consumer ProductRecycling Rate Plastic bottles10 – 35 % Glass containers25 – 35 % Steel Cans50 – 60 % Aluminium Cans50 – 70 % Lead batteries70 – 95 %

5. Current Method - Pyrometallurgy *For 10,000 tpy plant Capital: $4- 5M Energy: 14,000MWH *Independent Consultants

6. Lead Recycling 50 % of Pb from waste battery (Pb alloy grid + Pb paste)  Pb + Pb oxides + PbSO 4 (smelted at 1450 K) → Pb + CO 2 + SO 2  Done either in independent units or with primary smelting units  Energy: 4 - 10 kWh/Kg of Pb + pollution  Energy from a battery < 35 Wh/Kg

7. Environmental Issues Lead fuming is intensified at T > 500 o C Vapours and dust of Pb/PbO and gaseous SO 2 /SO 3 in the vicinity of smelters Smelter slags may contain up to 5 % Pb and such slags can release Pb by weathering Na slags that can fix most of the sulfur dissolve Pb even more readily

8. Some Other Recent Advances Leaching (fixes S with soda ash, usually incompletely) – Precipitation – Smelting (SO 2 & C penalty) Leaching (powerful reagents) – Electrowinning (capital and power intensive) @ 2 - 12 kWh/Kg to produce metallic electrodeposited Pb Shipping!

9. Battery Manufacture Lead is then chemically oxidised to PbO for the battery industry PbO is electrochemically reduced to Pb and oxidised to PbO 2 to make anode and cathode Current recycling processes are unsustainable from energy considerations Recycling> 2- 10 KWh/kg; Energy available from a battery < 50 Wh/kg

10. Table 1Range of Compositions from a dry lead battery paste MaterialWt % Lead sulphate55-65 Lead dioxide15-40 Lead monoxide5-25 Metallic lead1-5 Carbon black, plastics, fibres, other sulphates 1-4

11. Lead containing Organic Crystalline Compounds PbO Precursor New A new process for recycling lead battery waste → ↓ ↑ → Special Leaching/Crystallization Process Lead Battery Combustion/ Calcination Process Manufacturing Lead Battery Waste Battery Paste New Paste Patent: PCT/GB2007/ 004222; WO2008/056125 RV Kumar, S Sonmez and V Kotzeva

12. A new process for recycling lead battery waste → Paste Pb Grid Heat Energy from paste recycling New Grid New Paste directly from paste recycling Kettle Waste Battery New lead Battery

13. Green PB Recycling Process Patent: PCT/GB2007/ 004222; WO2008/056125 RV Kumar, S Sonmez, V Kotzeva Used Paste Crystalline Compoun ds PBO Precur sor New Past e New Battery Wast e Batt ery Leaching Combustion- Calcination Spent Lead grid Metallic Lead Energy

14. PbO leaching with citric acid solution PbO + C 6 H 8 O 7 ·H 2 O → [Pb(C 6 H 6 O 7 )]·H 2 O + H 2 O  Molar Ratio: PbO/ C 6 H 8 O 7 ·H 2 O= 1:1  Temperature: 20 ℃  Solid/Liquid=1/3;  concentration of citric acid monohydrate : 23.9 wt%  Magnetic stirring speed : 500rpm  Reaction time : 60min

15. Leaching of battery paste Ratio of Paste/ reagent

16. PbO 2 leaching experiment with citric acid solution  Filtration of Crystalline lead citrate  Pb recovery 99.9 % Leaching solid products and recovery ratio 239.2g/mol 415.32g/mol PbO 2 + C 6 H 8 O 7 ·H 2 O + H 2 O 2 → [Pb(C 6 H 6 O 7 )]·H 2 O + 2H 2 O +O 2 ↑

17. PbSO 4 leaching experiment with citric acid solution PbSO 4 +1.5 Na 3 C 6 H 5 O 7.2H 2 O + C 6 H 8 O 7 ·H 2 O → [Pb(C 6 H 6 O 7 ) n ] ·H 2 O + + Na 2 SO 4 + 2H 2 O  Molar Ratio: PbO 2 / C 6 H 8 O 7 ·H 2 O= 1:1  Temperature: 20 ℃  Solid/Liquid: 1/5  Magnetic stirring speed : 500rpm  Reaction time: 60min Leaching reaction conditions

18. 1. Lead citrate synthesis from PbO: 2. Lead citrate synthesis from PbO 2 : 3. Preparation of sodium citrate from sodium hydroxide and citric acid: 4. Desulphurisation of PbSO 4 by sodium citrate: Reactions of Interest Lead IV Oxide Hydrogen Peroxide Citric Acid Lead Citrate OxygenWater NaOH Citric Acid Sodium Citrate Water Lead Sulphate Sodium Citrate Lead Citrate Sodium Sulphate Water Lead II Oxide Citric Acid Lead Citrate Water

19. Lead organic crystallites

20. Combustion - Calcination Conversion of lead organic crystallites into PbO at relatively low temperatures (300- 500 O C) Source of Energy – Combustion of Organics embodied in the crystallites ( C-neutral) Direct production of PbO raw material for battery manufacturing Any ratio of PbO/Pb or PbO/PbO 2 is achievable – Direct production of Anode or Cathode also possible Energy for recycling 250 Wh/kg, of the same order of magnitude as energy from the battery 30 Wh/kg

21. Combustion product of PbO 2 leaching product Combustion products at the different combustion temperatures in Stationary air atmosphere At temperatures< 300 ℃, amorphous PbO structure At T > 350 ℃, crystalline PbO is the main product As T is increased, the ratio of PbO/ Pb increase

22. Thermal Analysis of organic precursor DSC/DTA at Stationary air atmosphere 128.4 ℃ endothermic peak, dehydrate peak 280.3 ℃ exothermic peak, 1st step combustion 345.0 ℃ exothermic peak, 2th step combustion Weight loss after combustion is 36.8% Air flow at 100cm 3 per minute 117.77 ℃ endothermic peak, dehydrate peak 284.16 ℃ exothermic peak, 1st step combustion 357.91 ℃ exothermic peak, 2th step combustion 2427J/g heat release from combustion process 873.27 ℃ endothermic peak, PbO melting point Weight loss after combustion is 38.33%

23. Combustion product of PbSO 4 leaching product Combustion products at the different combustion temperatures in Stationary air atmosphere Combustion at different temperatures for 1 hour After 350 ℃, weight loss is constant at 37.6% Pb/PbO ratio is calculated from wt loss [Pb 3 (C6H6O7) 2 ]·H2O → 3PbO 1019.6 g/mol 3*223.2 g/mol Ideal weight loss = (1019.6-3*223.2)/1019.6 = 33.7% [Pb 3 (C6H6O7) 2 ]·H2O → 3Pb 1019.6 g/mol 3*207.2 g/mol Ideal weight loss = (1019.6-3*207.2)/1019.6 = 39%

24. Results – Thermo Gravimetric Analysis –The graph below shows an example TGA analysis –The progressive decrease in weight can be attributed to the combustion/calcination of the lead citrate as it loses CO 2 and H 2 O and changes to PbO –The differential of the curve allows for a more easy comparison between cases

25. PbO by combustion-calcination SEMTEM

26. The Green PB Process For 10,000 tpy plant Capital: $1-1.5 M Energy: 1750 MWH

27. Carbon Impact: 10,000 tpy plant Acid from Renewable sources Acid from Non- Renewable sources

28. Sustainability  Current methods: energy required for recycling- 2 to 10 kWh/kg; energy produced by the battery per cycle: 35 - 50 Wh/kg  Using our new process, energy produced by a lead battery is comparable to energy for recycling: 150 - 250 Wh/kg  Low-C impact from C-neutral source of energy embodied in the leaching reagent

29. Further Research Work at the University Further research Tramp elements removal and recovery Low-cost industrial grade citric acid sourcing and production Improved battery pastes for high energy/ power density batteries Lightweight Batteries via new materials for grids and separators/electrolytes

30. CONCLUSIONS Recycling of lead acid batteries is considered within the overall context of materials and energy sustainability Direct recovery of lead as lead oxide is proposed New research for high energy density lead acid battery is being carried out