Findings and opportunities from the 2012 NSF SusChEM workshop

Chair: Susannah Scott Department of Chemistry & Biochemistry; Department of Chemical Engineering

University of California, Santa Barbara

Co-chair: Jim McGuffin-Cawley Department of Materials Science and Engineering

Case Western Reserve University

Disclaimer: The views herein represent the author’s, and are not necessarily those of the NSF.

Ensuring the Sustainability of Critical Materials and Alternatives: Addressing the Fundamental Challenges in Separation Science and Engineering

244th ACS National Meeting, Philadelphia, August 21, 2012

SusChEM

Sustainable Chemistry, Engineering, and Materials • Systems-level thinking is required: “There are no sustainable parts of unsustainable wholes.” Franzi Poldy, CSIRO

• More fundamental research should be use-inspired. • Green is not synonymous with sustainable. • Efficiency is necessary but not sufficient, due to the rebound effect • Sustainability research and education is multidisciplinary and collaborative.

Workshop topics

• Discovering new chemistry and materials that will replace rare, expensive and/or toxic chemicals with earth-abundant, inexpensive and benign minerals and chemicals,

• Discovering new processes to economically recycle chemicals and materials that cannot easily be replaced, such as phosphorus and the REE’s,

• Discovering new chemistry to convert non-petroleum based sources of organics to feedstock chemicals,

• Discovering new environmentally-friendly chemical reactions and material processes that use less energy, water, and organic solvents than current practice,

• Incorporate sustainability into the curriculum; have earth, physical and social scientists and engineers take common courses; and promote entrepreneurship.

Many separations-relevant issues

• Mineral processing and element recycling (including urban mining) – Rare earths – Precious metals – Phosphorus

• Chemical process intensification – Integrated reaction/separation in microflow reactors – Improved separation designs in conventional chemical processing

• Membranes

– Scaleable polymer-inorganic composites – Highly selective metal-organic frameworks (MOFs)/porous coordination polymers (PCPs)

• Simplifying complex product streams from biomass-derived sources

Uses of rare earths

X. Du, T. E. Graedel, “Global In-Use Stocks of the Rare Earth Elements: A First Estimate”, Environ. Sci. Technol.,

2011, 45, 4096.

Light rare earths (LREEs) Heavy rare earths (LREEs)

LREEs

HREEs

cata

lyst

s

cata

lyst

s

Ce Nd La Pr

Dy Y Gd Sm Tb Eu

Concentration of supply

"There is oil in the Middle East; there is rare earth in China…" Deng Xiaoping, 1992

China now produces almost all of the world’s supply of REEs. Light REEs: from Bastnäsite-containing ores in Inner Mongolia Heavy REEs: adsorbed on laterites (clays) in Southern China

X. Du, T. E. Graedel, “Global In-Use Stocks of the Rare Earth Elements: A First Estimate”, Environ. Sci. Technol., 2011, 45, 4096.

Environmental and social costs Bayan Obo LREE open pit mine, Baotou, Inner Mongolia, China

Each ton of rare metals mined releases: • 10 – 12 x 103 m3 of waste gas (dust, HF, SO2, H2SO4); • 75 m3 acidic wastewater; • 1 ton radioactive waste residue (Chinese Society of Rare Earths)

Acid tanks and run-off ponds at HREE mining facility near Ganzhou, Jiangxi Province, China

Photos by Adam Dean. The Telegraph, 19 March, 2011.

“Green” technologies

A Toyota Prius contains 30 kg RE: NiMH battery (La, Ce) electric motor/generator (Nd, Pr, Dy, Tb) LCD screen (Eu, Ce)

A 3 MW wind turbine contains 600 kg RE: permanent magnets (Nd, Pr, Dy, Tb)

A single compact fluorescent lightbulb contains 1.5 g RE: phosphor (principally Eu, with smaller quantities of La, Dy, Ce, Pr and Gd)

Chi

nese

exp

ort q

uota

s, k

T

Rare earth export quotas • In 2010, China cut REE export quotas dramatically. • In late 2012, China announced separate export quotas for LREEs and HREEs.

www.bloomberg.com

REO 2009 2010 2011 8/2012

La 5 22 104 20

Ce 4 22 102 21

Nd 19 50 234 105

Pr 18 48 197 110

Sa 3 14 103 70

Dy 116 232 1450 950

Eu 493 560 2843 2020

Tb 362 558 2334 2000 http://www.lynascorp.com

Prices in US $/kg, FOB China

China’s rationales: • Rare earths are strategic resources. • Manufacturing high value finished products is preferred over export as low value raw materials. • Need to consolidate and regulate REE production, to better control pollution.

Rare earth processing

http://www.gwmg.ca

Solvent extraction

Mixer-settlers used for continuous, counter-current liquid-liquid extraction of RE ions, in a demonstration plant in Australia.

About 600 mixer-settler boxes are required for an integrated separation facility, due to low per-stage efficiency (typically, < 3).

Ln3+ ions partition into a non-polar organic solvent containing a ligand such as R2P(O)OH or R3PO.

R. Wormsbecher, Grace

Rare earth recovery

Recycling of REEs is almost non-existent, due to the high cost of separation. “Distribution entropy” affects recovery prospects: • Nd has a high distribution entropy.

– Hard drives, DC motors, permanent magnets, headphones • La has a lower distribution entropy.

– Metal hydride battery cathodes, hybrid cars, fluid catalytic cracking (FCC) catalyst

• Active component in FCC catalyst is La-

exchanged USY • An FCC unit processing 75,000

barrels/day contains 56,000 tons catalyst with ca. 1,000 tons RE

• Catalyst lifetime is ca. 1 month • World consumption is ca. 2,300 tons

catalyst/day (10% of all RE use) • Spent catalyst contaminated with other

metals (Ni, V) is landfilled or used for construction aggregate

R. Wormsbecher, Grace

Challenges for RE separation and recovery Aim to reduce energy-, water- and chemical-intensity. Make recycling economically viable. 1. Design new chelating agents for highly selective solvent extraction 2. Replace low efficiency mixer-settlers by high efficiency centrifugal contactors 3. Explore new solvent systems (e.g., RTIL, scf)

4. Develop high affinity ion-exchange resins

5. Develop rare earth-selective membranes

Peterman et al., Separ. Sci. Technol. 2010, 45, 1711

E. Peterson, Idaho National Lab R. Wormsbecher, Grace

Global food security

warned of impending global famine in address to the British Acad. Sciences (1898)

Sir William Crookes

Guano mining in the Central Chincha Islands (Peru), mid-19th century

The Atacama Desert (Chile), with the Andes visible in the background. The remains of a nitrate plant (late 19th

century) and its tailings pile can be seen in the middle. P. Marr, “Ghosts of the Atacama: The abandonment of nitrate mining in the Tarapacá region of Chile”, Middle States Geographer, 2007, 40, 22.

The N-revolution

J. W. Erisman, M. A. Sutton, J. Galloway, Z. Klimont, W. Winiwarter, “How a century of ammonia synthesis changed the world”, Nature GeoSci. 2008, 1, 636.

Fritz Haber Alwin Mittasch Carl Bosch

Phosphorus in agriculture

Brazilian corn plants grown on P-treated soil are much taller than control plants like those in the foreground, which did not receive adequate additional phosphorus. UNEP Year Book 2011.

Large pile of bison skulls to be ground into fertilizer, ca. 1870. Photo courtesy of Burton Historical Collection, Detroit Public Library.

There is no P-analog of the Haber-Bosch process. “There are no substitutes for phosphorus in agriculture.” USGS

P = essential macronutrient

P is required in: hydroxyapatite, amino acids, nucleic acids, phospholipids, ATP, creatine phosphate

Adults must ingest 0.7 g P/day in their food. Children, adolescents, and pregnant women should consume 1.25 g/day. Symptoms of P deficiency (hypophosphatemia): loss of appetite, muscle weakness, bone pain, rickets, fragile bones, increased susceptibility to infection, numbness and tingling of the extremities, difficulty walking Severe hypophosphatemia results in death.

O 43 kg

C 16 kg

H 7 kg

N, 1.8 kg Ca, 1.0 kg

P, 0.8 kg other, 0.4 kg

World phosphorus supply

K. Ashley, D. Cordell, D. Mavinic, “A brief history of phosphorus: From the philosopher’s stone to nutrient recovery and reuse”, Chemosphere, 2011, 84, 737.

0.5 Bt phosphate rock has been extracted over the past half-century. Current global extraction rate is 20 Mt/year.

Production is increasing at 2.5 % / year.

Mining phosphate rock Phosphorite, a sedimentary rock

15-20 % phosphate, as Ca5(PO4)3X (X = F, OH)

Florida mines pump 100,000 gallons water/min. Rock may contain elevated levels of toxic metals (Cr, Cd, Pb, Hg).

Each ton of mined rock generates 5 tons radioactive (U, Th) phosphogypsum.

Open-cast mining of phosphate rock

Togo Florida

Phillippe Diederich for The New York Tim

Phosphate use efficiency

Only 20% of mined phosphate ends up in the food we consume.

P recoveries from phosphate rock can be as low as 40%.

Peak phosphorus?

Peak phosphorus curve derived from US Geological Survey and industry data, indicating peak production ca. 2035.

Cordell, D.; Drangert, J.-O.; White, S. The story of phosphorus: Global food security and food for thought.

Glob. Environ. Change 2009, 19, 292.

Global phosphate reserves

Largest current producers: China (38%), US (15%), Morocco (14%), Russia (6%)

Future P-rock needs

D. Cordell and S. White, “Peak Phosphorus: Clarifying the Key Issues of a Vigorous Debate about Long-Term Phosphorus Security”, Sustainability 2011, 3, 2027

Estimated reserves will last 300-400 years at current production rates. Growing world population, food equity, and changing dietary preferences (increased protein consumption) could reduce this to 50-100 years.

Supply/price instability

• Prices shot up in 2007–2008, due to increasing demand driven by more meat- and dairy-rich diets, especially in China and India, and to expansion of the biofuels industry.

• In 2008, China imposed a 135 % tariff on phosphate rock, effectively eliminating exports. It was lifted in 2009, but new peak season tariffs were introduced in 2011 and remain in effect. • Phosphate recovery becomes economically viable at $100/t.

“Failure to take a systems approach could result in investment in costly and energy-intensive phosphorus recovery technologies that do not address the whole system and hence do not provide the greatest outcome for sustainability, or at worst, conflict with other related services (such as energy supply).” Cordell, 2011

P-recovery from cities

Humans excrete 3 Mt P annually (0.4 kg/person/yr). Some forms struvite, MgNH4PO4.6H2O (MAP). Potential use as slow-release fertilizer.

Pipe clogged with struvite, due to increase in phosphate concentration during biological wastewater treatment.

Conventional precipitation-sedimentation-filtration is energy-intensive, and product has high water content (60-80 %).

In 2012, a municipal Nutrient Recovery Facility opened in Hillsboro, Oregon. It will produce 1200 tons/yr of CrystalGreen fertilizer. Ostara reports seven times less energy required to create Crystal Green than conventional fertilizer.

www.ostara.com

Crystallization in liquid fluidized bed

Phosphate recovery plant in Westerbork, The Netherlands

• MgNH4PO4.6H2O is obtained by mixing feed with MgCl2 and (if necessary) NaOH • Difficult separation of fine crystals

• fluidized bed crystallizer uses seed (sand or minerals) to induce pellet formation • product discharged continuously at bottom • high purity pellets with low water content (< 5%)

www.dhv.com

Crystalactor®

Other potential P-recovery approaches: adsorption, ion-exchange, nanofiltration.

Closing the P-cycle

1. Improve recovery of phosphate from phosphate rock, while mitigating impact of waste. 2. Replace as much primary input as possible by secondary input (recycled P) • Devise efficient ways to recycle P from animal waste • Recycle P from other phosphorus uses (e.g., phosphines and phosphine oxides used in chemical processing, phosphors used in lighting) • Capture P from diffuse sources (detergents in graywater, farm runoff)

K. Lammertsma, Amsterdam

Extracting by-products

• Need to increase extraction efficiency from ores • Reduce dependence on strong acid solutions during processing • Develop methods to extract Re from alloys for recycle

crushing, milling, flotation concentrates Mo

100 ppm Re

during roasting, Re2O7 sublimes in flue gas

500 ppm Re

mining Cu ore 1 ppm Re

Re2O7 is dissolved in weak acid solution

1000 ppm Re

organic solvent extraction 2% Re

ion-exchange then crystallization as

NH4ReO4, 69% Re

reduction by H2 to metal > 99.9% Re

1

2

3

4

5

6

7

Re metal

molybdenite

Re annual production 50 tons; supply is inelastic. Used in gas turbines and jet turbines, where fuel efficiency increases with operating temperature. In some super-alloys, Re is unsubstitutable. Projected need for 30,000 new, fuel-efficient passenger planes by 2030. Supply > demand; Re price $12,000/kg in 8/2008.

British Geological Survey

M. Carducci, D. Honecker, Climax Molybdenum

K. Jensen et al., Angew. Chem. Int. Ed. 2010, 49, 899

Process intensification

K. Jensen et al., Angew. Chem. Int. Ed. 2007, 46, 5704

Replace batch reactors with continuous microflow reactors - superior mixing and heat transfer properties - safer handling of hazardous intermediates - possibility of using short-lived reactants - easy to ‘number-up’ Need to couple with appropriately scaled separations systems

New membrane materials

S. Nair, Georgia Tech

AMH-3 3D porous layered silicate

surface functionalized with organosilane

dispersed in cellulose acetate (CA)

Inorganic-organic hybrid membranes combine the separating ability of the porous inorganic component with the processibility and scaleability of the organic component. Nanodispersion of the inorganic filler increases discrimination between molecules of different sizes. Potential uses in CO2 and H2S capture.

Chemicals from renewables

A = Hydrolysis B = Isomerization C = Dehydration D = Rehydration E= Hydrogenation F = Hydrogenolysis

N. Cardona-Martínez, UPRM-Mayagüez

Educational needs • Prepare a qualified, knowledgeable workforce to think about how its actions affect the sustainability of the process/product/company/etc. - Train students in systems-level thinking, economic and safety analyses using case studies - Ask students to conduct life cycle and material flow analyses - Expose students to industrial research and design with constraints - Have students reflect on scaleability, materials availability, desired lifetime and recyclability - Cultivate communication skills with stakeholders, including the public

• Emphasize multidisciplinary teamwork (physical scientists/engineers/social scientists) • Make sustainability training part of professional accreditation requirements (ACS, ABET, AIChE, TMS, ACerS, MRS) • Empower students to create change through innovation training and experiences

Acknowledgements

SusChEM Co-chair Jim McGuffin-Cawley (Case Western Reserve)

NSF Division Directors Matt Platz (CHE), Jim McGrath (CBET), and Ian Robertson (DMR)

Many NSF Program Officer observers, especially Kathy Covert, Tingyu Li, and Lynnette Madsen

All SusChEM workshop participants, from academia, industry, and government, especially our grad students