๐ Case Study
Gold Tailings Geochemical Stabilization at Granny Smith Mine (WA)
Arsenic-rich tailings (up to 120 mg/kg As) exhibiting elevated As leaching under oxidizing conditions
๐๏ธ Project Overview
Granny Smith gold operation (Western Australia), 2019โ2022
๐ฏ Challenge
Arsenic-rich tailings (up to 120 mg/kg As) exhibiting elevated As leaching under oxidizing conditions
๐ง Design Approach
Lime-assisted arsenic immobilization + ferric sulfate co-precipitation; verified via kinetic column tests and PHREEQC batch modeling
๐ Design Diagram
AI-generated project design illustration
๐ Key Calculations
As Sorption Capacity
qโ = KโยทCโ/(1+KโยทCโ)
Result: 18.4 mg/g
Guided lime dosing for target residual [As] < 0.1 mg/L
Fe/As Molar Ratio
(FeยทMW_As)/(AsยทMW_Fe)
Result: 12.6
Ensured complete As co-precipitation as scorodite
๐ Results
Leachate [As] reduced from 0.82 mg/L to <0.03 mg/L; 10-year stability confirmed by 24-month column tests๐ก Lessons Learned
- โขpH >7.5 essential for arsenate adsorption
- โขFerric iron must be freshly precipitated โ aged FeOOH less effective
- โขColumn test duration must exceed 12 months for regulatory acceptance
- โขPHREEQC batch models underestimated sorption at low As concentrations without surface complexation extension
- โขField-scale lime blending uniformity was the largest operational risk factor
โ Key Takeaways
- 1pH >7.5 essential for arsenate adsorption
- 2Ferric iron must be freshly precipitated โ aged FeOOH less effective
- 3Column test duration must exceed 12 months for regulatory acceptance
- 4PHREEQC batch models underestimated sorption at low As concentrations without surface complexation extension
- 5Field-scale lime blending uniformity was the largest operational risk factor