Sabodala-Massawa Gold Mine: BIOX and CIL Recovery Methods

Source: Endeavour Mining plc (2026)
Website: https://www.endeavourmining.com/our-portfolio/sabodala-massawa-mine/

Critical Data

Overview

Endeavour Mining plc operates the Sabodala-Massawa Mine in Senegal, a world-class gold mining complex featuring two integrated processing plants: the Sabodala Whole Ore Leach Plant (SWOLP) and the Sabodala Sulphide Treatment Plant (SSTP). The SWOLP, commissioned in 2009 and upgraded in 2020, treats free-milling ores through a conventional SABC (semi-autogenous grinding, ball milling, and pebble crushing) circuit followed by carbon-in-leach (CIL) and gravity concentration. Its design capacity is 4.2 Mt/a (dry) handling a blend of oxide and fresh ores. The SSTP, commissioned in Q2 2024, treats refractory ores using flotation to produce a sulphide concentrate, which is then oxidized in a BIOX® circuit (licensed from Metso) before cyanidation in a dedicated CIL circuit. The SSTP has a design throughput of 1.2 Mt/a (dry). Together, these plants process ore from multiple open pits and underground sources along the Sabodala and Massawa shear corridors, managing variable feed grades, mineralogy, and weathering profiles. The combined Life-of-Mine gold production is projected to peak at 391 koz in 2029, driven by high-grade Kerekounda & Golouma underground ores feeding the SWOLP, while the SSTP processes predominantly fresh ore from Massawa CZ and Massawa NZ. The integrated design shares utilities and services, maximizing operational efficiency and gold recovery from both free-milling and refractory resources.

Key Process Stages

• Stage 1: ROM Handling and Primary Crushing – Free-milling ore is delivered to two parallel primary crushing trains (Metso C140 jaw crushers) with vibrating grizzlies, reducing ROM from 800 mm to a P80 of ~150 mm. A secondary cone crusher (Sandvik CH660) further reduces a middlings fraction to −20 mm. For refractory ore, a dedicated Metso C120 jaw crusher feeds a 19 m³ surge bin after blending on finger stockpiles based on sulphur and gold grade.
• Stage 2: Comminution and Gravity Recovery – The SABC circuit comprises a 4 MW SAG mill, two parallel 4 MW ball mills, and Metso HP200 pebble crushers for the SWOLP, while the SSTP uses a 2.8 MW SAG mill and a 2.8 MW ball mill with a Metso HP100 pebble crusher. Both circuits achieve a target grind P80 of 90 μm. A portion of the cyclone feed is diverted to a centrifugal gravity concentrator; concentrate undergoes intensive cyanidation (ICR) with dedicated electrowinning, and tails return to the ball mill feed.
• Stage 3: Flotation and Regrind (SSTP) – The SSTP flotation circuit treats the milled slurry in two rougher tank cells, three scavenger cells, and three cleaner cells. Collector (PAX, 65 g/t) and frother (MIBC, 50 g/t) are added. Rougher and cleaner concentrate is reground in a VTM-200 vertical stirred mill (150 kW) to a target P80 of 45 μm to liberate sulphide minerals. Flotation tailings report to a thickener, with the option to route to the SWOLP for additional recovery.
• Stage 4: BIOX® Bio-oxidation and CCD – Reground flotation concentrate (nominal 11.8 t/h dry solids, 44 t S²⁻/d) is fed to four parallel primary BIOX® reactors (1,368 m³ each) followed by three secondary reactors in series. Total residence time is 6.7 days at 40–42°C and pH 1.3–1.4, achieving 94.2–96.1% sulphide oxidation. The oxidized slurry is washed in a three-stage counter-current decantation (CCD) circuit (97% wash efficiency) and neutralized with limestone (314 kg/t conc) and lime (44 kg/t conc) to pH 7.0 in six stages.
• Stage 5: CIL, Elution, and Gold Recovery – The neutralized product enters a dedicated CIL circuit with six tanks (36 h residence time) using sodium cyanide (20.8 kg/t) and lime (20 kg/t) at pH 10.5. Loaded carbon (up to 4,500 g/t Au) is stripped in a split AARL elution column (6 t capacity, 6 strips/week). Gold is electrowon onto stainless steel cathodes, smelted into doré bars. CIL tails undergo SO₂/air cyanide destruction before disposal. The SWOLP uses a similar 8 t elution system at 8 strips/week.

Additional Interesting Data and Summary

The Sabodala-Massawa processing complex demonstrates industry-leading integration of conventional and advanced recovery technologies. Historical performance shows the SWOLP consistently exceeded its 4.2 Mt/a design, milling 4.76 Mt in 2023 and 4.47 Mt in 2025, with actual gold recoveries ranging from 79% to 89% depending on feed blend. The SSTP, despite being in its early years, achieved 76% recovery in 2025 with a head grade of 3.77 g/t. Process inputs for the SWOLP in 2025 included 30.5 kWh/t electrical power, 0.57 m³/t water, 0.59 kg/t grinding media, 1.72 kg/t lime, and 0.32 kg/t sodium cyanide. The SSTP consumed higher reagents due to the BIOX® process: 71.57 kWh/t, 11.25 kg/t lime, and 0.90 kg/t cyanide in 2025. Budgeted consumption for 2027 projects improvements: SSTP power dropping to 59.46 kWh/t and lime to 8.40 kg/t. Environmental management includes tailings thickening (SWOLP underflow 60–65% solids) and a dedicated lined compartment (TSF1B) for SSTP CIL tails. Cyanide destruction via SO₂/air ensures compliance. The LoM production schedule forecasts combined gold recovery peaking at 391 koz in 2029, declining to 58 koz by 2034 when the SWOLP ceases operations. The SSTP is slated to end in 2032. Future sustainability initiatives focus on blending high-arsenic Massawa NZ ore with Massawa CZ to maintain Fe:As >2.8, reducing acid consumption and limestone demand. The integration of gravity circuits in both plants enhances early gold capture, reducing inventory and improving overall recovery. As refractory ore sources deplete, the facility underscores the importance of continuous optimisation in reagent consumption, water recycling, and energy efficiency to extend economic viability while maintaining robust gold production.

Key Processes: Flotation, CIP/CIL, Cyanidation, Gravity Separation, SAG Mill, Ball Mill, Crushing

Target Commodities: Gold, Copper, Lead