Comprehensive Recovery& Sustainable Development of Phosphate Resources

Comprehensive Recovery& Sustainable 

Development of Phosphate Resources 

Patrick Zhang 

Florida Industrial & Phosphate Research Institute 

(formerly Florida Institute of Phosphate Research) 

Florida Industrial and Phosphate Research Institute

Phosphate Is an Energy Mineral 

• Well known fact: phosphate is a crop nutrient 

(providing energy for plants) mineral, key to 

production of food that provides energy for 

mankind 

• Less known truth: phosphate is also a energy 

mineral 

– Uranium (nuclear energy) 

– Rare earths (green energy) 

– Thorium (green nuclear energy) 

Phosphate could power the world!

Summary of World Phosphate Mining 

• Production reaching 200 million tons/year 

• Surface mining dominates 

• Washing is common, producing slime 

• Flotation is the major technology for upgrading 

• Dolomite (carbonate) is a worldwide problem 

• Permitting is becoming a global challenge 


Three Sustainable Development 

Approaches 

• Improving P 2 O 5 recovery 

• Waste treatment and utilization 

• Comprehensive recovery 


Improving Phosphate Recovery 

• Improving P 2 O 5 recovery in the mining process 

Current mining recovery

Remote LIBS (Laser-Induced 

Breakdown Spectroscopy) Analyzer 

• Distant (5-25 m) 

real-time chemical 

analysis of 

phosphate 

minerals 

• Correlation 

coefficient of R 2 = 

0.915 for P 2 O 5 . 


Types of Phosphate Ores Based on 

Beneficiation Difficulty

Direct-Reverse Flotation of 

Carbonaceous Phosphate Ores 

Feed with -0.074mm fraction accounting for 98.4% 

Na2CO3, 5.0Kg/t 

Na2SiO3 , 4.0Kg/t 

YP 2-1 

, 1.8Kg/t 

YP 1 

, 0.3Kg/t 

YP 2-1 

, 0.9Kg/t 

YP 2-1 

,0.5Kg/t 

H 2 

SO 4 

, 6.4Kg/t 

YP 2-3 

, 0.5Kg/t 

Concentrate 

Carbonate Tailings 

Silicate Tailings

Utilization of Low-grade Phosphate: The 

Improved “Hard” Process

Advantages of the Improved “Hard” 

Process 

• Increased overall phosphate recovery 

• Use of low-grade rock 

• No clay ponds 

• No PG generation 


Major Wastes Generated by the 

Phosphate Industry 

• Slime 

• Phosphogypsum 

• Slags 


Phosphatic Clay Statistics - Florida 

• About a ton of clay generated for each ton of rock 

• Nearly 100,000 tons produced per day, disposed of 

as 3% solids slurry 

• Over 3 million tons of slurry per day 

• 30-40% mined lands used as clay settling areas 

Florida 

Florida 

Institute 

Industrial 

of Phosphate 

and Phosphate 

Research 

Research Institute

Basic Properties of Florida 

Phosphatic Clays 

• Averaging 9% P 2 O 5 

• Containing ±50% clay minerals 

• Containing up to 40% of the REE in phosphate ore 

• Containing about 30% of the U in phosphate ore 

• Extremely fine, 90% below 20microns 

Florida 

Florida 

Institute 

Industrial 

of Phosphate 

and Phosphate 

Research 

Research Institute

Potential Uses of Waste Clay 

• Tile 

• Light weight aggregates 

• Polymer modified waste clay as concrete additive 

to increase ductility and strength 

• Recovery of P, U and rare earths 

Florida Industrial and Phosphate Research Institute 

Florida Institute of Phosphate Research

“Wet Process” Phosphoric Acid 

Production and Phosphogypsum (PG) 

Ca 10 F 2 (PO 4 ) 6 + 10H 2 SO 4 + 10nH 2 O → 

10CaSO 4 •nH 2 O (PG) + 6H3PO4 + 2HF 

• Di-hydrate process, n=2 

• Hemi-hydrate process, n=1/2 

• Hemi-Di-hydrate process, n=2 


World Phosphogypsum Statistics 

• Calculation basis: 

o Annual rock production 200 Mt 

o 70% of the rock is used for wet acid production 

o 4.5tons of PG produced per ton of P2O5 produced 

o P2O5 in rock averaging 30% 

• Annual world PG production 189 Mt 


Problems with Phosphogypsum Stacks 

• Spills of process water on top of PG stacks 

• Possible groundwater contamination 

• Occupy a significant amount of land 

• Can be located in highly sensitive, 

increasingly populated areas 

• Costs of opening, operating and closing 

stacks 


Research Has Been Conducted on More 

Than 50 Uses of Phosphogypsum 

Landfill Chemical Agriculture Construction 

Waste destruction 

Energy generation 

S recovery 

(NH 4 ) 2 SO 4 

CaO 

Sodic soil treatment 

Acidic soil treatment 

Ca source 

S source 

P source 

Mg source 

Road base 

Cement 

Building blocks 

Wall boards 

Brick 

Sand substitute 

Aggregate substitute 


Successful PG Uses in Agriculture 

• The exchangeable Ca in PG can ameliorate 

subsoil acidity and Al 3+ toxicity and reclaim 

sodic soils. PG is also known for its capability of 

improving soil structure by flocculating clays in 

soil. 



• PG contains nutrients Ca, S and P 

• PG enhances root growth thus helping plants 

absorb other nutrients, especially 

• Dissolution of PG in soil provides essential 

electrolytes to maintain hydraulic conductivities 

and increase infiltration rates thus preventing 

crusting and reducing erosion. 



• Application of 500 lbs PG per acre tripled 

NCS31 peanut yield in Georgia, USA 

• Use of PG more than doubled apple yield while 

increasing calcium content in Brazil 

• Application of 176 lbs PG per acre nearly 

doubled crimson clover yield in Florida, USA 

• Application of 4.5 ton PG per hectare on a sodic 

soil increased cotton yield by at least 40% in 

Kazakhstan 


World Potential for Agricultural 

Phosphogypsum Consumption 

• World crop area is >4.5 billion hectares 

• At an application rate of 0.1 ton/hectare/yr, 

450 million tons/yr could be consumed 

• Agriculture has the potential to consume all 

the PG the phosphate industry produces 


PG Use in Construction in China 

• Cement retarder 

• PG board with paper cover 

• PG blocks 

• Bricks

PG Use in Roads 

• PG makes a superior road base at a significantly 

lower cost than conventional road base materials 

• PG dries fast after rain falls thus down time in 

road construction 

• PG roads get better with aging 


PG Use in Roads – Cost Comparison 

Item 

Cost, $/mile 

Tanner Road Windy Hill 

Parrish Road 

Road with PG 

Materials 35,009 47,719 0 

Labor 28,912 38,408 9,511 

Equipment 34,418 43,193 13,974 

Total 98,339 129,320 23,485 


PG Use as a Chemical Raw Material 

Industrial Operations in China 

• Sulfur recovery 

• Ammonium sulfate production: Wengfu Group’s 

250,000 tons plant consuming 50% of waste CO2 

gas from their ammonia plant ammonium sulfate 

per year 


Use of Phosphogypsum -Challenges 

• Low product values 

• Transportation costs 

• Sulfur price flocculation 

• Government regulations and public perception 

with regard to radiation (particularly in Florida)

Use of Phosphogypsum - Opportunities 

• Promotion by various entities, IAEA, FIPR, 

Aleffgroup, Wengfu Group, GCT, OCP, Vale, 

Paradeep… 

• Large PG use plants have been built recently in 

China, and some may come on line soon in India 

and Brazil 

• Government efforts 

– China’s new plan calling for 30% use of PG by 2025 

– Guizhou Province set the goal for zero PG 

accumulation by year 2025

Production of Ammonium Phosphates 

Demands for Phosphoric Acid 

• The first wet-acid plant built in Germany 1870 

• The first wet-acid plant in the U.S. in 1890 

• Thermal processes (using either blast furnace or 

electric furnace) dominated during the early 

phosphate booming years 

• Since 1950, the wet acid process has quickly 

overtaken the thermal method 

• Today only about 5% of the world phosphate rock 

is consumed by the thermal process

World Phosphate Rock Consumption 

by Category 

10% 

0.50% 

5% 

Wet acid 

13.50% 

SSP 

Others (animal feed, FMP, 

MKP, TSP, NPK, NP) 

71% 

Thermal phosphorus 

Direct application

“Wet Process” Phosphoric Acid 

Production and Phosphogypsum (PG) 

(fluorapatite) Ca 10 F 2 (PO 4 ) 6 + 10H 2 SO 4 + 10nH 2 O 

→ 10CaSO 4 •nH 2 O (PG) + 6H3PO4 + 2HF 

• Di-hydrate process, n=2 

• Hemi-hydrate process, n=1/2 

• Anhydrite, n=0 


Comprehensive Recovery: Treating 

Phosphate as an Energy Mineral 

• Well known fact: phosphate is a crop nutrient 

(providing energy for plants) mineral, key to 

production of food that provides energy for 

mankind 

• Less known truth: phosphate is also a energy 

mineral 

– Uranium (nuclear energy) 

– Rare earths (green energy) 

– Thorium (green nuclear energy) 

Phosphate powers the world!

Average Uranium and Thorium Contents 

(ppm) in Selected Phosphate Ores 

Sample No. of sample U Th 

Florida, USA pebble, 1926-1935 11 208 14 



Florida, USA Pebble, 1994 3 95 -- 

North Carolina, USA, 1957-1964 3 79 9 

Utah, USA, 1936-1961 9 128 7 

Idaho, USA 5 151 8 

Peru, washed rock, 1961-1964 7 106 8 

Morocco, 1937-1943 5 141 8 

Tunisia,1927-1955 6 48 23 

Jordan, 1956-1963 6 48 0 

Egypt, 1936-1937 6 122 6 

Senegal 6 107 17

Uranium in Selected Phosphate Rock 

and Phosphoric Acid Samples (ppm) 

Location U 3 O 8 in Rock U 3 O 8 in Phosphoric 

Acid (30% P 2 O 5 ) 

Algeria 110-140 130 

Brazil 80 80 

Israel 50-150 165 

Jordan 120-150 165 

Morocco 90-140 140 

Tunisia 50-100 80 

Florida 150-180 190 


Uranium in Phosphate: Basic Facts 

• Concentration ranging from 50 to 200 ppm, 

averaging +100 ppm 

• Worldwide annual U unrecovered from 

phosphate totaling 18 million kg (based on 

180Mt rock production) 

• Worldwide total U resources toping 29 billion kg 

(based on total phosphate resources of 290 

billion tons) 


Uranium in Phosphate Accounting for 

88% of the World’s Unconventional U 

Unconventional U 

Lignite, 2% 

Black Shale, 8% 

Phosphate, 88% 

Other, 2% 

Source: Harikrishnan Tulsidas, IAEA, 2012

Form of Uranium in Phosphate Rock 

• Normally 65% as U 4+ , & 35% as U 6+ 

• U 4+ exists in isomorphous substitution for Ca 

• U 6+ is held by chemisorbtion on surface as 

UO 2 .HPO 4 

• In igneous phosphate U could also be associated 

with thorium (232Th) and rare earths 


Fate of Uranium in the Wet Acid & 

Fertilizer Manufacturing Processes 

• 80-90% in phosphoric acid 

• 10-20% in phosphogypsum (PG) 

– About 10% in dihydrate PG 

– Up to 20% in hemihydrate PG 

• Nearly all the U in the acid ends up in fertilizers 


Recovery of Uranium from Phos. Acid 

• Industrially proven in numerous plants and twice 

in the history 

• No mining costs 

• Easy to permit 

• Saving a resource otherwise forever lost 

• Other elements of value (Th and REE) can be 

recovered from the same liquid 


Techniques for Uranium Extraction 

from Phosphoric Acid 

• Solvent extraction (SX), the industrially proven 

process 

• Ion exchange (IX), the intensively investigated 

method with many promises 

• Precipitation, the “abandoned” process? 


Solvent Extraction Based Technologies 

for U Recovery from Phosphoric Acid 

in Sulfate Media 

• DEPA-TOPO (also DEHPA-TOPO, D2EHPA- 

TOPO) uses di(2-ethylhexyl) phosphoric acid 

and trioctyl phosphine oxide as extractants 

(ORNL process) 

• OPAP uses octyl phenyl acid phosphate as 

extractant (ORNL process) 

• OPPA uses octyl pyro phosphoric acid as 

extractant (Dow process)

Three Major SX Systems 

Process Extractant Formular 

OPPA 

D2EHPA/TOPO 

DEPA/TOPO 

Octyl pyrophosphoric acid 

Dissolving P 2 O 5 in octyl 

alcohol in the absence of 

moisture and below 15 o C 

A mixture of di(2-thylhexyl) 

phosphoric acid and 

trioctyl phosphine oxide, 

{H3C(CH2)7}3-P=O 

where R is CH3.(CH2)6.CH2- 

OPAP process 

A mixture of mono and 

di-octylphenyl 

phosphoric acids and tributyl 

phosphate, (C4H9O)3-P=O

DEPA/TOPO Based Process: 

Pretreatment 

• Cooling 

‣ To precipitateNa 2 SiF 6 and CaSO 4 and improve SX efficiency 

• Flocculation-filtration 

‣ To remove precipitates 

• Absorption with activated carbon or sand 

‣ To remove organics 

• Oxidation (with H 2 O 2 , O 2 , or Fe +2 ) 

‣ To convert all U to hexavalent form 



Two-cycle Extraction 

• First cycle 

‣ In a counter-current mixer/settler system, clarified acid is 

contacted with DEPA-TOPO solvent dissolved in kerosene; U 

is transferred to the organic phase. Lean phosphoric acid is 

returned to the phosphoric acid plant. 

• First cycle stripping 

‣ The organic phase containing uranium in the U 6+ state is 

reduced to the U 4+ state; it is then contacted with more 

concentrated phosphoric acid in a second mixer/settler system. 

Here the U is stripped from the relatively large volume of 

organic solvent and transferred to the smaller volume of a 

stripping acid.


Two-cycle Extraction 

• Second cycle extraction 

‣ The loaded primary stripping acid is oxidized to convert uranium 

back to the U 6+ state. The strip acid is then contacted with DEPA- 

TOPO solvent in a mixer/settler system, where concentrated U is 

transferred to the solvent phase and further concentration takes 

place to form “pregnant secondary organic”. 

• Second cycle stripping 

‣ The pregnant secondary organic containing the U is contacted 

with an alkaline solution in a mixer/settler system. Here the U 

is stripped from the organic solvent and transferred to the 

alkaline solution in a more concentrated form. The secondary 

strip solution is treated to neutralize the alkali and produce an 

acidic uranium solution.


Oxidizing & Refining 

• The acid uranium solution is oxidized: 

− with hydrogen peroxide to form uranyl peroxide UO4·nH2O 

− with ammonia to form ammonium diuranate (ADU), (NH 4 ) 2 U 2 O 7 

− with to ammonium carbonate (or ammonia+CO 2 ) to form 

ammonium uranyl tricarbonate (AUT), (NH 4 ) 4 U 2 O 7 (CO 3 ) 3 

• Thicken, wash, dry, and calcine the above 

products to produce U 3 O 8 – yellow cake 


Second Wave Uranium Recovery Plants 

Acid 

Producer 

Farmland 

Uranium 

Producer 

Wyoming 

Minerals 

Freeport 

Location 

Capacity 

P 2 O 5 

(tons/year) 

Capacity 

U 3 O 8 

(lbs/year) 

Pierce, FL 450,000 400,000 

Process 

WMC, DEPA- 

TOPO 

Freeport 

Minerals Co. Uncle Sam, LA 675,000 690,000 FMC, DEPA- 

TOPO 

Agrico 

Freeport Donaldsonville, 

FMC, 

360,000 420,000 

Minerals Co. LA 

DEPA-TOPO 

IMC IMC New Wales, FL 1,000,000 800,000 

IMC, DEPA- 

TOPO 

CF Industries IMC Bartow, FL 720,000 600,000 

IMC, DEPA- 

TOPO 

CF Industries IMC Plant City, FL 680,000 600,000 

IMC, DEPA- 

TOPO 

W. R. Grace 

Uranium 

Recovery 

Operating 

Period 

1978 – 1981 

1978 - 1999 

1981 - 1998 

1980 - 1992 

1981 - 1985 

1980 - 1992 

Bartow, FL na 330,000 URC, OPAP 1976 – 1980 

Gardinier Gardinier East Tampa, FL 500,000 420,000 Gardinier, OPPA 1979 – 1982 

Western 

Coop. 

Fertilizer 

Earth 

Sciences 

Calgary, Alberta, 

Canada 

Chemie Rupel Umipray Purrs, Belgium 100,000 150,000 

144,000 120,000 ESI, OPAP 1981 – 1987 

IMC – Prayon, 

DEPA-TOPO 

1980 - 1998

Uranium Recovered from 

Phosphoric Acid in the USA 

Millions Kg of U3O8 

1.5 

1 

0.5 

0 

1978 1982 1986 1990 1994 1998 

.

U Recovery from Concentrated Phos. 

Acid from Hemihydrate Process 

• Solvent DEPHA + TOPO proved to be 

effective. 

• Both the technical and economic feasibility 

demonstrated for uranium recovery from 

hemihydrate acid (40-45% P 2 O 5 ) were 

demonstrated. 


Solvent Extraction Based Technologies 

for U Recovery from Phosphoric Acid 

via Nitric Acid Digestion 

• Tributyl phosphate (TBP) 

• Tertiary amyl alcohol 


Advantages of the Nitrate Route 

• No phosphogypsum problem 

• Suitable for in-situ or heap leaching of low 

grade phosphate ores 

• Better for REE recovery 

• More complete REE dissolution by nitric acid 

• Both extractants capable of picking up REE 

while extracting U 



Challenges 

• Fluctuating uranium prices 

• Unfavorable public perception and political 

atmosphere about nuclear power due to the 

accident in Japan 

• Industry fatigue 

• Industry becoming more risk averse 



Opportunities 

• Advances in technologies –ion exchange 

• IAEA’s UxP program 

• Resource utilization efficiency consideration 

• Nuclear energy tremendously appealing for 

curbing global warming 

• Simultaneous recovery of REE and Th 


Recent/Current Efforts to Recover 

Uranium from Phos. Acid 

• Florida companies completed new feasibility 

study and plant design 

• OCP Group’s commercialization plans 

• Pilot testing program in Egypt 

• Pilot testing program in Tunisia 

• Urteck pilot testing 

• FIPR program in conjunction with the CMI 

• Joint efforts by K-Technologies & Kemworks

Egyptian Pilot Testing Program on 

Uranium Recovery from Phosphoric 

Acid 

• Capacity: 1 cubic meter of acid per hour 

• Has been conducted on and off for 10 years 

USF Polytechnic - Florida Industrial and Phosphate Research Institute

Pretreatment Tanks 

Each tank can hold 

20 tons of acid 


Acid Pre-treatment Columns 

Carbon columns 

are short, and sand 

columns are tall 


First Cycle Extraction 

4 mixer-settlers for uranium 

extraction from pretreated 

phosphoric acid (with 60 

ppm uranium) using a 

mixture of 0.5 M D 2 EHPA & 

0.125 M TOPO in Kerosene . 

Acid flow rate: 1 m 3 /hr; 

organic flow rate: 330 L/hr. 


First Cycle Stripping 

Three mixer-settlers for 

uranium stripping from 

loaded organic solvent using 

diluted pure phosphoric acid 

(36 % P 2 O 5 ) containing iron 

powder 


Second Cycle Extraction/Stripping 

11 mixer-settlers: 4 for uranium 

extraction (0.3 M D 2 EHPA & 0.075 

M TOPO in kerosene) from diluted 

acid produced from the primary 

unit; 3 for organic scrubbing by 

using distilled water; 2 for uranium 

stripping by ammonium carbonate; 

finally 2 for washing stripped 

organic using sulfuric acid. 


The Tunisia Pilot Plant for U Recovery 

A Lasting and High Profile Program

Unique Features of the Tunisia Pilot 

Plant for U Recovery 

• Purification and concentration (from 40-56% 

P 2 O 5 ) of phosphoric acid 

• Use of columns for extraction instead of 

mixer/settler


Phosphoric Acid Purification


Columns Are Used for Extraction


Acid Pre-treatment and Purification

Recent R&D Efforts: Pilot Testing of 

IX Technology by Urtek 







The portable demonstration plant was 

commissioned in May 2012 and operated in the 

United States during June to August 2012 on 

phosphoric acid streams from two fertilizer 

facilities. 


Summary of Urtek Pilot Testing 

• Consistently high uranium recovery (> 90%) 

• No crud formation 

• Reagent consumptions within expected range 

• Purification and concentration of uranium 

achieved without significant uranium losses 

• Phosphoric acid chemistry unchanged except for 

the removal of uranium and other impurities 


Urtek Pre-feasibility Study: Base Case 

• 1M short ton of P 2 O 5 phosphate facility 

• 880,000 lbs of uranium per annum 


Urtek Pre-feasibility Study: Cost 

Numbers 

• Cash operating costs: $18/lb of U3O8 

• Consumables: $6.70/lb of U3O8 

• Labor: $1.10/lb of U3O8 

• Maintenance: $3.20/lb of U3O8 

• Misc. $4.90/lb of U3O8 

• Contingency $1.50/lb of U3O8 

• Capital cost: $156 million 


REE in World Phosphate Rock 

Lanthanide Content (Krea and Khalaf, 2000) 

Rock Source Ln 2 O 3 (%) 

Kola, Russia 0.84-0.88 

Florida pebble 0.29 

Algeria 0.13-0.18 

Morocco 0.14-0.16 

China, Zhijin 1.29 

Tunisia 0.14 


Phosphates with High REE 

• A Canadian phosphate deposit near Quebec 

containing 1800 ppm of REE 

• A Canadian phosphate deposit in Ontario 

having 1.59% La2O3+Ce2O3 

• Recently discovered phosphate deposits in 

northern China with REE concentration 

(total R 2 O 3 ) ranging from 1.5%~6.41% 

USF Polytechnic - Florida Industrial and Phosphate Research Institute

REE in Phosphate Rock 

• Rare earths constitute 0.01 to 0.1% of the apatite, 

averaging 0.05% REE oxides 

• About 200 million tons of phosphate rock 

processed annually 

• REE may be recovered together with uranium 


Rare Earth Elements in the Phosphate 

Deposits of the Tethys 

• The Tethys covering Algeria, Egypt, Iran, Iraq, 

Jordan, Libya, Morocco, Syria, and Tunisia 

• Phosphate deposits totaling 90 billion tons 

• Averaging 300 ppm REE 

• Containing 27 million tons of REE resources 


Recovery of REE from Phosphate 

Opportunities 

• Global interest in diversifying REE supplies 

• Newly established US Critical Materials Institute 

• Possibility of enriching REE in the liquid phase 


Recovery of REE from Phosphoric 

Acid 

• One of the solvents, di-2-ethylhexyl phosphoric 

acid (D2EHPA), for extracting uranium from 

phosphoric acid was found to be effective for 

extracting REE from phosphoric acid. 

• Technical feasibility has been demonstrated. 


Recovery of REE from Phosphoric 

Acid (continued) 

• Research showed that REE leaching efficiency 

into the phosphoric acid phase could be increased 

to 75% by three methods: 

‣ lowering leaching temperature 

‣ reducing the solid/liquid ratio in the reactor 

‣ adding surfactant to enhance gypsum crystal growth 

thus reducing REE adsorption 


Recovery of REE from Phosphate: 

Commercialization 

• Industrialized Ural Federal University (Russia) 

technology for extracting REE from phosphate 

via nitric acid leaching and solvent extraction 

• Possible commercialization of the Prayon 

technology for REE extraction from 

phosphogypsum via sulfuric acid leaching 

• New solvent developed for simultaneous 

extraction of REE and thorium 


Recovery of REE from Phosphate: 

The Florida Case Study 

• A significant amount of REE-containing 

concentrate can be obtained from flotation 

tailings by simple gravity separation. 

• REE in waste clay may be concentrated 

• Dihydrate process is relatively easy to modify to 

increase REE dissolution 


Other Recoverable Elements from 

Phosphate Rock 

• Iodine 

• Anhydrous hydrogen fluoride 

• Wengfu Group 

100 tons of iodine 

50,000 tons of anhydrous hydrogen fluoride

Closing Remarks: The Triangle of 

Sustainable Development of Phosphate 

Improving 

P 2 O 5 

Recovery, 

Mining, 

MgO Issue 

Economic 

Other wastes: 

Slag, tailings, 

process water… 

Waste 

Utilization, 

PG & Slime 

and 

Social 

Good 

Recovery 

of Energy 

Values, 

U, REE ,Th 

Other elements: 

I, F…

Comprehensive Recovery& Sustainable Development of Phosphate Resources

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