Gold Recovery Methods at Serabi’s Palito Complex Plant

Source: Serabi Gold plc (2026)
Website: https://www.serabigold.com/operations/palito-complex/

Critical Data

Overview

Serabi Gold plc operates a 500 tonnes-per-day (t/d) gold processing facility at the Palito Complex, located in Pará State, Brazil. The plant processes ore from both the Palito and São Chico mines using an integrated flowsheet that combines crushing, grinding, ore sorting, copper flotation, carbon-in-pulp (CIP) cyanidation, intensive leaching, elution, electrowinning, and smelting to produce doré bars. Established well before the effective date of the 2026 NI 43-101 Technical Report, the plant has been operating continuously with consistent performance. Its significance lies in the ability to treat two different ore types efficiently: Palito ore undergoes copper flotation to recover a high-grade copper concentrate carrying 50–70% of the gold, while the flotation tailings report to CIP cyanidation for residual gold and silver recovery. São Chico ore feeds a separate grinding circuit with gravity concentration and intensive cyanide leaching of the concentrate. The combination of ore sorting for low-grade material, selective flotation, and cyanidation ensures a high overall gold recovery, which reached 96.7% in 2025. The facility also processes historical flotation tailings, achieving an average recovery of 77.0% from those stockpiles. The entire process is designed to maximize gold extraction while producing a marketable copper concentrate and a final doré product shipped offsite for refining.

Key Process Stages

• Stage 1: Crushing – ROM ore is crushed to minus 15 mm using a primary jaw crusher (Metso 6240E, 56 kW), secondary (Faço 60S) and tertiary cone crushers (Faço 60TF and Sandvik H2800) in closed circuit with a double-deck vibrating screen (Simplex SXP 4015/2D). Oversize (+38 mm) returns to secondary crushing; intermediate fraction (-38+15 mm) low-grade material is diverted to the ore sorter. Final product P80 is 12–15 mm at an average feed rate of 35 t/h.
• Stage 2: Ore Sorting – Low-grade Palito ore (-38+15 mm) is upgraded using a Comex CXR-1000 X-ray/optical sorter. Material is washed over an 8 mm screen before being presented as a single layer on a high-speed conveyor. Each particle is scanned by photometric color and XRT sensors; a computer algorithm classifies particles and directs air jets to separate product from waste. The sorted product (9.79 g/t average grade) is returned to the crushing circuit, while waste (0.64 g/t) is stockpiled. Commissioned in 2020, the sorter has processed 163,207 tonnes of feed through 2025.
• Stage 3: Grinding and Gravity Concentration – Three parallel ball mill circuits grind ore to 80% passing 120 µm. Circuit 1 (Humboldt Wedag 2.3×3.2 m, 253.6 kW) processes Palito ore for flotation. Circuit 2 (Zanini 2.2×3.5 m, 205.2 kW) grinds São Chico ore and includes a Falcon SB-750B centrifugal concentrator (7.5 kW) to recover free gold. Circuit 3 (Zanini 2.2×3.5 m, 205.2 kW) can treat either ore type. Cyclone overflow from Palito circuits reports to flotation; São Chico overflow combines with flotation tailings for CIP.
• Stage 4: Intensive Leaching & Copper Flotation – São Chico gravity concentrate is leached in a Gekko In-line Leach Reactor (ILR150) in 800 kg batches using 1.5% NaCN and hydrogen peroxide for 24 hours. The leach solution is circulated through an electrowinning cell (600×600 mm, 25.4 kW) in the gold room. Palito ore undergoes flotation in a conditioning tank followed by rougher, scavenger, and cleaner cells (Emprotec dual cells, 22.8–22.4 kW each). Collector A3894 and lime (pH 10–11) are used. Rougher concentrate ( >20% Cu) is filtered via an Andritz filter press; scavenger tails go to CIP. Flotation recovery captures 50–70% of the gold in Palito ore into a copper concentrate shipped offsite.
• Stage 5: CIP Cyanidation, Elution & Gold Refining – Flotation tailings and São Chico gravity tails are combined in two leach tanks (185 m³ each) and six adsorption tanks (74 m³ each) providing ~18 hours retention at 35% solids. Cyanide is maintained at 250 ppm NaCN in leach, attenuating to ~100 ppm. Carbon concentration is 20 g/L (40 g/L in first tank). Loaded carbon is acid washed with 2% HCl, then eluted at 130°C using the Zadra process (1.5 t capacity column). Pregnant solution passes through electrowinning cells (Como Eng, 25.4 kW each). Gold/silver sludge is dried, fluxed, and smelted in a Grion 11 L furnace at 1,200°C to produce doré bars. Each elution cycle averages 15 hours. Barren carbon is regenerated at 750°C in a Kemix kiln (75 kg/h) before returning to the circuit.

Additional Interesting Data and Summary

The Palito processing plant demonstrated robust operating performance from 2014 to 2025, processing over 2 million tonnes of milled ore with an average head grade of 6.80 g/t and a consistent gold recovery of 92.0% for milled ore. In 2025 alone, 208,999 tonnes of ore at 6.80 g/t yielded 44,169 ounces of gold at a record recovery of 96.7%. The plant also processed 139,411 tonnes of historical flotation tailings between 2015 and 2023, achieving an average recovery of 75.8% and contributing 11,361 ounces of gold. Key consumables include sodium cyanide (1.10 kg/t in 2025, representing ~50% of consumable cost), steel balls (1.28 kg/t, ~25% of cost), lime (1.95 kg/t), and sodium metabisulfite for cyanide detoxification (0.65 kg/t). The ore sorter, commissioned in 2020, processed 163,207 tonnes of low-grade Palito ore through 2025, upgrading feed at 1.73 g/t to a product averaging 9.79 g/t while rejecting 88% of the mass at 0.64 g/t, thereby reducing mill feed costs and waste volumes. Environmental management includes cyanide detoxification using the INCO air/SO2 process in a dedicated tank (93 m³, 1.5 hours residence) to reduce CNWAD to <5 ppm before tailings disposal. The plant’s continuous improvement is evidenced by the installation of new 185 m³ leach tanks in 2022–2023, boosting CIP retention time. Production peaked in 2025 at 44,169 ounces of gold, and the operation remains a cornerstone of Serabi’s Brazilian gold production. The integration of gravity concentration, flotation, and cyanidation allows flexible processing of variable ore types, maximizing overall gold and copper value recovery. Forward-looking, the plant’s proven performance and established infrastructure support sustained production from the Palito and São Chico deposits, with potential for additional throughput from ore sorting upgrades and further tailings retreatment campaigns.

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

Target Commodities: Gold, Silver, Copper