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

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

Lead Battery (> 80 % Lead Usage)

Lead Batteries- Leaders in Recycling

Consumer Product Recycling Rate

Plastic bottles 10 – 35 %

Glass containers 25 – 35 %

Steel Cans 50 – 60 %

Aluminium Cans 50 – 70 %

Lead batteries 70 – 95 %

Current Method - Pyrometallurgy

*For 10,000 tpy plantCapital: $4-5MEnergy: 14,000MWH*Independent Consultants

Lead Recycling

50 % of Pb from waste battery (Pb alloy grid + Pb paste)

Pb + Pb oxides + PbSO4 (smelted at 1450 K) → Pb + CO2 + SO2

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

Environmental Issues

Lead fuming is intensified at T > 500oC Vapours and dust of Pb/PbO and gaseous

SO2/SO3 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

Some Other Recent Advances

Leaching (fixes S with soda ash, usually incompletely) – Precipitation – Smelting (SO2 & C penalty)

Leaching (powerful reagents) – Electrowinning (capital and power intensive) @ 2 - 12 kWh/Kg to produce metallic electrodeposited Pb

Shipping!

Battery Manufacture

Lead is then chemically oxidised to PbO for the battery industry

PbO is electrochemically reduced to Pb and oxidised to PbO2 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

Table 1 Range of Compositions from a dry lead battery paste

Material Wt %

Lead sulphate 55-65

Lead dioxide 15-40

Lead monoxide 5-25

Metallic lead 1-5

Carbon black, plastics, fibres, other sulphates

1-4

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; WO2008/056125RV Kumar, S Sonmez and V Kotzeva

A new process for recycling lead battery waste

→

Paste

Pb GridHeat Energy from pasterecycling

New Grid

New Paste directly from paste recycling

Kettle

Waste Battery

New lead Battery

Green PB Recycling Process

Patent: PCT/GB2007/004222; WO2008/056125RV Kumar, S Sonmez, V Kotzeva

Leaching

Combustion-Calcination

SpentLead grid

MetallicLead

Energy

PbO leaching with citric acid solution

PbO + C6H8O7·H2O → [Pb(C6H6O7)]·H2O + H2O

Molar Ratio: PbO/ C6H8O7·H2O= 1:1Temperature: 20 ℃Solid/Liquid=1/3; concentration of citric acid monohydrate : 23.9 wt%Magnetic stirring speed : 500rpmReaction time : 60min

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0 5 10 15 20 25 30 35 40 45 50 55 60 65

Reacti on Ti me/ mi n

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1.5 : 1 1.25 : 1 1 : 1

Leaching of battery paste

Ratio ofPaste/reagent

PbO2 leaching experiment with citric acid solution

Filtration of Crystalline lead citratePb recovery 99.9 %

Leaching solid products and recovery ratio

239.2g/mol 415.32g/mol

PbO2 + C6H8O7·H2O + H2O2→ [Pb(C6H6O7)]·H2O + 2H2O +O2↑

PbSO4 leaching experiment with citric acid solution

PbSO4 +1.5 Na3C6H5O7.2H2O + C6H8O7·H2O → [Pb(C6H6O7) n ] ·H2O + + Na2SO4 + 2H2O

Molar Ratio: PbO2/ C6H8O7·H2O= 1:1Temperature: 20 ℃Solid/Liquid: 1/5Magnetic stirring speed : 500rpmReaction time: 60min

Leaching reaction conditions

101520253035404550

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Temp

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1. Lead citrate synthesis from PbO: 

  2. Lead citrate synthesis from PbO2: 

  3. Preparation of sodium citrate from sodium hydroxide and citric acid: 

  4. Desulphurisation of PbSO4 by sodium citrate:

 

 

Reactions of Interest

Lead organic crystallites

Combustion - Calcination

Conversion of lead organic crystallites into PbO at relatively low temperatures (300- 500OC)

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/PbO2 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

Combustion product of PbO2 leaching productCombustion 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

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 100cm3 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 process873.27 endothermic peak, PbO ℃melting point Weight loss after combustion is 38.33%

Combustion product of PbSO4 leaching productCombustion 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

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Temperature(℃)

Loss

of

weig

ht(w

t%)

[Pb3(C6H6O7)2]·H2O → 3PbO

1019.6 g/mol 3*223.2 g/molIdeal weight loss = (1019.6-3*223.2)/1019.6 = 33.7%

[Pb3(C6H6O7)2]·H2O → 3Pb

1019.6 g/mol 3*207.2 g/molIdeal weight loss = (1019.6-3*207.2)/1019.6 = 39%

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 CO2 and H2O and

changes to PbO

–The differential of the curve allows for a more easy comparison between

cases

PbO by combustion-calcination

SEM TEM

The Green PB Process

For 10,000 tpy plantCapital: $1-1.5 MEnergy: 1750 MWH

Carbon Impact: 10,000 tpy plant

Acid from Renewable

sources

Acid from Non-

Renewable sources

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

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

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