Recycle and Recovery of Critical Materials from Pyrometallurgical Waste Austin Blumenthal Hunter Chase Megha Gandhi Sara Viau Advisor Dr. Corby Anderson

Background Recycling of critical/precious metals has become significant in the past decade as known sources of these metals are depleting Gopher Resources (Our Sponsor), a lead-based battery recycler, produces 99.95 % pure lead or special lead alloys through their refining process Drossing, a process used to remove impurities like Copper, is currently used by Gopher Resources

Background (cont.) Caustic dross addition meant to remove As & Sb Sulphur drosses remove Cu impurities No specified step for Ni removal Gopher Resources partnership around leaching of the impurities present after Caustic Drossing

Scope Gopher Resources sent us sample from Caustic Dross (CCW) & Sulfur Dross (DECO) Focus of this study on CCW slag sample leaching The CCW slag sample contains 25 wt% lead which is normally fed back into lead smelter to adjust melt chemistry. Copper, Nickel, and Arsenic are impurities in lead slag which are detrimental to producing lead products Hydrometallurgical extraction methods could be used to economically recycle this slag to increase Pb value

Analysis of As-Received Cold Caustic Wash XRF Results MLA Results

Analysis of As-Received Cold Caustic Wash Quantitative phase analysis difficult to decipher Oxide phases determined appropriate leaching reagents

Fundamentals of Science Used Leaching is a method used to dissolve solids into their ionic forms Factors that affect leaching conditions include the following: Solubility Reagents Selectivity Regeneration Furthermore, the right Eh and pH conditions are significant in determining the right leaching conditions Finally, the shrinking core model demonstrates the heterogeneous kinetics that is taking place in the reactor

Pourbaix Diagrams Copper Diagram Nickel Diagram

Experimental Method Leach experiments tested four factors: Residence Time: From 4 hours to 8 hours Temperature: From 25 to 75 degrees celsius Sulfuric Acid Concentration: From 20 to 50 g/L Hydrogen Peroxide: From 0 to 10 g/L Design Expert was used to generate runs for a 24-1 factorial design with 3 midpoints

Experimental Method- Experimental Matrix

Results and Discussions Recovery of Nickel, Copper, and Arsenic for variant operating conditions

Results and Discussions Potential and pH for the 11 runs at variant conditions

Results and Discussions Free acid titrations conducted at room temperature for 11 runs

Leach Optimization Design Expert was used to produce computer models of each response ORMULAS]

Leach Optimization- Ni Response Cube

Leach Optimization- Cu Recovery Contour

Leach Optimization- Nickel Recovery Contour

Leach Optimization- Final Results Temperature: 75 C Residence Time: 4 hours Sulfuric Acid Concentration: 50 g/L Sulfuric Acid Peroxide Concentration: 4.22 g/L Hydrogen Peroxide Recovers 74.3 wt% Cu, 22.5 wt% Ni, and 54.0 wt% As

Leach Optimization- Copper Recovery

Leach Optimization- Mass Balance

Process Design Criteria- Flow Sheet 10 tons of CCW per day 2 leach vessels (each 10,000 gallons) 20 wt. % solids for leach Production of Cu/Ni Carbonates Production of iron arsenates

Economic Analysis - OpEx & CapEx Hourly Labor Cost, USD $179,316.80 Salaried Labor Cost, USD $0.00 Electrical Cost, USD $171,500.00 Maintenance and Repairs Cost, USD $423,850.00 Natural Gas Cost, USD $30,625.00 Hydrogen Peroxide Cost, USD $225,806.68 Operating Supplies Cost, USD $63,577.50 Laboratory Charges Cost, USD $26,897.52 Total Annual Operating Cost, USD $1,121,573.50 Fixed Capital Estimate, USD $4,966,025 Working Capital Estimate, USD $744,903.74 Total Capital Estimate, USD $5,710,928.68

Economic Analysis Capital Expense, USD $5,710,928.68 Annual Operating Expense, USD $1,121,573.50 Annual Revenue, USD $ 1,310,713.60 Discount Rate, % 5.0% Net Present Value, USD $-4,250,438.94 Internal Rate of Return, % -16.3% Payback Period, months 363

Economic Analysis

Conclusions Our proposed design recovers 74.3 wt% copper, 22.5 wt% nickel, and 54.0 wt% arsenic Agitated leaching and ionic precipitation methods were used to selectively remove and recover the impurities While design has a positive yearly cash flow, the magnitude of flow does now pay back capital costs at a feasible rate.

Future Work Leach optimization with additional factors- slurry density and particle size AA on copper recovery Replicate studies should be conducted to verify results

Acknowledgements Dr. Corby Anderson Dr. Joe Grogan PhD Candidate Hao Cui Majuba Hill Senior Design Group

References [1] T. Ellis and A. Mirza. “The refining of secondary lead of use in advanced lead-acid batteries”, Elsevier: Journal of Power Sources, Jan. 2010. Web. 18 Jan. 2017. [2] P. Tan and P. Vix. “Thermodynamic Modeling of copper drossing process in lead refining”, TMS, 2006. Web. 18 Jan 2017. [3] C. Gupta and T. Mukherjee, Hydrometallurgy in extraction processes, 1st ed. Boca Raton: CRC Press, 1990, p. 462. [4] Geogene And Anthropogenic Controls On The Mineralogy And Geochemistry Of Modern Alluvial-(Fluvial) Gold Placer Deposits In Man-Made Landscapes In France, Switzerland And Germany. Hannover: Journal of Geochemical Exploration 99(1):29-60, 2017. Web. 1 Apr. 2017. [5] Anderson, C.G. The Shrinking Core Model Lecture # 36 2016. Kroll Institute for Extractive Metallurgy, George S. Ansell Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO. [6] G. Wyss. “Characterization of Lead Processing Samples”, CAMP, 3 March, 2017.

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