Zonia Copper Heap Leach: Conventional SX-EW Recovery Methods

Source: Edge Copper Corporation (2026)
Website: https://edgecopper.com/zonia/

Critical Data

Overview

The Zonia Copper Project, operated by Edge Copper Corporation (TSX.V: EDCU), is a proposed open-pit mining operation in Yavapai County, Arizona, designed to produce LME Grade A copper cathodes through a conventional copper–acid heap leach system. The 2026 Preliminary Economic Assessment (PEA) outlines a fully integrated recovery process that includes two-stage crushing, agglomeration with sulphuric acid and raffinate, heap leaching on a dual-lined pad, solvent extraction (SX), and electrowinning (EW). The project operates on a 365-day, 24-hour basis and targets a nominal crush size of P80 1.5 inches. Heap leach pads are constructed in three phases, with a total footprint of approximately 16.8 million square feet, and are designed to handle up to 20 lifts of 26 feet each, reaching an ultimate height of 525 feet. The SX circuit uses two extraction stages and one stripping stage, while the EW circuit consists of two parallel banks with 130 polycement cells. The entire SX/EW circuit is designed as a closed-loop, zero-discharge facility, minimizing environmental impact. The Zonia site’s location in Arizona benefits from established mining infrastructure and a favorable regulatory environment, supporting the project’s economic viability. The recovery methods are conventional yet robust, ensuring high copper recovery and production of market-ready cathodes.

Key Process Stages

• Stage 1: Two-Stage Crushing Circuit — Run-of-mine (ROM) ore is fed to a gyratory crusher reducing to nominal 6 inches, then conveyed to double-deck vibrating screens. Screen oversize passes through secondary cone crushers operating in open circuit, while undersize (0.6 inch) reports to the fine-ore stockpile. The target final crush size is P80 1.5 inches (38 mm). A dust-collection system controls fugitive emissions. Crushing circuit availability is 75%, allowing for maintenance.
• Stage 2: Agglomeration Drums — Crushed ore is reclaimed from the stockpile via four vibrating feeders and fed to agglomeration drums. Here, raffinate and fresh sulphuric acid are added to deliver approximately 50% of total acid demand while keeping moisture between 8% and 10% by weight. The agglomerated material is then conveyed via overland conveyor and portable grasshopper conveyors to the heap leach pad.
• Stage 3: Heap Leaching — Agglomerated ore is stacked in 26 ft lifts using a radial stacker in retreat mode. After curing for up to five days, drip irrigation applies raffinate at 0.0025–0.005 gpm/ft². Leaching occurs over approximately 90 days per cell. Pregnant leach solution (PLS) flows by gravity through a perimeter ditch to the PLS pond. An event pond handles the 1-in-100-year, 24-hour storm. The pad uses a double HDPE/LDPE liner system with leak detection.
• Stage 4: Solvent Extraction (SX) — PLS is pumped to the SX circuit comprising two extraction stages and one stripping stage in conventional mixer-settler tanks. Copper is transferred from the aqueous phase to an organic oxime/kerosene mixture, then stripped into a high-concentration acid solution (lean electrolyte) to produce rich electrolyte. Raffinate is recycled to the heap and agglomeration circuit.
• Stage 5: Electrowinning (EW) — Rich electrolyte is purified via column flotation and filtration to remove entrained organics and solids. The polished solution enters the EW tank house with two parallel banks of 130 polycement cells, each containing 60 cathodes (10 ft² each). Cobalt sulphate (up to 200 ppm) and polyacrylamide are added as corrosion inhibitor and growth modifier. Plated cathodes are mechanically stripped, washed, sampled, and bundled as LME Grade A copper cathodes.

Additional Interesting Data and Summary

The Zonia Copper Project’s heap leach facility is engineered with a robust double-liner system (HDPE and LDPE) across a 16.8 million ft² footprint, ensuring maximum solution containment and environmental protection. The three-phase pad development provides approximately 227 million tons of stacked ore capacity over a 10.6-year mine life, with individual lift capacities ranging from 10 to 28 million tons per phase. The PLS pond holds 25.0 million gallons (24 hours of irrigation), the raffinate pond holds 6.2 million gallons (6 hours of SX return), and the event pond is sized at 35.4 million gallons to contain the 1-in-100-year, 24-hour storm with a 10% safety factor. The design includes leak detection and recovery systems (LDRS) with dedicated sumps and continuous flow monitoring. From an economic perspective, the conventional SX-EW circuit is well-established for copper recovery, and the closed-loop design minimizes fresh water consumption and eliminates liquid discharge. Sustainability initiatives include topsoil stockpiling for reclamation, stormwater reuse, and zero-discharge operations. The use of mechanized cathode stripping and automated sampling reduces labor and improves product consistency. Future geotechnical investigations will confirm the 525 ft maximum heap height. The project’s location in Yavapai County, Arizona, benefits from skilled workforce, road and power infrastructure, and proximity to copper markets. Overall, the Zonia Copper Project demonstrates a technically sound, environmentally responsible approach to copper production through conventional heap leaching and SX-EW technology.

Key Processes: Flotation, Heap Leaching, Gravity Separation, Crushing

Target Commodities: Copper