Heap Leach: Wetting Agents and Permeability | Academy

How to use this guide

This page is a procurement-friendly decision aid for operations, metallurgy, and EHS teams. Use it to align on: (1) the problem you’re solving, (2) selection criteria, (3) a safe and controlled trial plan, and (4) procurement-ready specifications you can verify at receipt.

If you share a few site details (heap height, ore type, irrigation method, pH system, recycle water quality, downstream circuit sensitivities), we can propose supply-ready options with a clear test plan and documentation expectations.

What “permeability” means in heap leaching

In heap leaching, permeability is the heap’s ability to accept, distribute, and drain solution without excessive ponding or preferential flow. Permeability is not only a “pore size” issue—it is strongly influenced by wetting behavior, fines migration, clay swelling/dispersion, scaling, biological growth, and solution chemistry.

Common permeability failure modes

Channeling / preferential flow: solution follows the same pathways, leaving “dry islands” and under-leached zones.
Ponding and surface sealing: solution accumulates at the surface; infiltration rate drops.
Fines migration: fine particles move and plug voids, reducing hydraulic conductivity.
Clay swelling / dispersion: clays expand or disperse in certain ionic conditions, closing flow channels.
Scaling / precipitation: gypsum, carbonates, silica, iron/aluminum salts can form deposits in pores and piping.
Biofouling: microbial growth creates slime layers or precipitates that restrict flow (site dependent).

What wetting agents do (technical overview)

Wetting agents are typically surfactant-based additives designed to lower surface tension and improve contact between leach solution and ore surfaces. In practical terms, they help solution enter small pores, spread over mineral surfaces, and reduce the tendency of droplets to bead or bypass hydrophobic zones.

Mechanisms that matter on a heap

Reduced surface tension: improves infiltration and distribution under drip or sprinkler application.
Improved capillary wetting: helps solution access micro-pores and partially saturated zones.
Lower contact angle: solution spreads rather than beads on hydrophobic or dusty surfaces.
Reduced interfacial resistance: can improve mass transfer at the solid–liquid interface (site dependent).
Controlled foaming behavior: essential for irrigation stability (a “good” wetting agent must not create operational foam problems).

Important: “wetting agent” is not one product type

Products vary widely: nonionic vs anionic blends, low-foam vs standard surfactants, different cloud points, salt tolerance, adsorption behavior on clays, and compatibility with downstream circuits. Selection must match your pH system (acid vs cyanide), water quality, and process constraints.

Where it fits in the process

Process goal: choose the KPI you are optimizing (recovery, cycle time, irrigation uptime, reagent consumption, or stability).
Operating window: pH, temperature, ionic strength (TDS), and solution residence time in the heap.
Application method: drip emitters vs sprinklers vs wobblers; target application rate and wetting pattern.
Downstream sensitivity: carbon adsorption, SX/EW, precipitation, thickening/clarification, or discharge rules.
Constraints: EHS requirements, biodegradability preferences, site rules, transport, and storage limitations.

When to consider wetting agents

Wetting agents are most valuable when distribution—not chemistry—is limiting recovery. Typical triggers include:

Uneven moisture profiles: dry zones observed in moisture surveys, heat mapping, or trench inspections.
Infiltration decline over time: ponding increases, irrigation pressure rises, or flow becomes unstable.
High variability across cells/lifts: some areas drain well while others remain wet or dry.
Recovery plateauing early: solution grades drop faster than expected, suggesting bypassing.
Dusty/hydrophobic ore behavior: fresh-crushed ore sheds water or forms beading under irrigation.

Key decision factors

Ore mineralogy: clay content/type (e.g., swelling vs non-swelling clays), fines fraction, hydrophobic carbonaceous material.
pH system: acid leach vs alkaline/cyanide; compatibility expectations differ.
Water quality: recycle water TDS, hardness, silica, sulfates; wetting agent performance can change in high salinity.
Temperature range: cold-weather viscosity and cloud point matter for consistent dosing.
Foam risk: irrigation turbulence, ponds, sumps, and recirculation can amplify foam if the product is not low-foam.
Downstream circuit risk: adsorption on carbon, interference with SX phase separation, clarification, or precipitation steps (site dependent).

Selection matrix (practical guidance)

Use this matrix to quickly frame the selection conversation. Exact chemistry should be confirmed with supplier data and a controlled trial.

Site condition	What it implies	What to ask for
High recycle water salinity / high TDS	Some surfactants lose efficiency or haze/phase separate	Salt tolerance data, stability in site water, low haze/precipitation behavior
Cold weather / low solution temperature	Risk of viscosity increase or clouding	Cloud point, pour point, viscosity vs temperature, winter handling guidance
Clay/fines sensitive ore	Adsorption and dispersion behavior can change permeability	Adsorption tendency, recommended ppm range, any clay compatibility notes
Foam-sensitive operations	Foam can reduce pumping stability and overflow capacity	Low-foam formulation, foam test data, defoamer compatibility (if needed)
Downstream SX/EW or adsorption circuit	Risk of phase separation issues or adsorption interactions	Compatibility statement, recommended monitoring signals, trial plan checkpoints
Strict EHS / discharge constraints	Preference for biodegradable, lower-toxicity chemistries	Up-to-date SDS, biodegradability/tox profile summaries, handling and spill guidance

Dosing and application (how teams typically approach it)

Dosing must be validated by a trial because heaps vary widely. Teams often begin with a conservative “screening range” and adjust based on infiltration response and foam behavior.

Typical starting points (screening guidance)

Initial screening dose: often in the low-to-mid ppm range in the irrigation solution (exact range depends on product and site water).
Step tests: increase in controlled steps while monitoring infiltration, ponding, and foam response.
Where to add: dose into a well-mixed recirculation tank or line with sufficient turbulence for dispersion; avoid dead zones.
Stability: confirm no precipitation, haze, or separation in site water (especially with high hardness/TDS).

Practical dosing calculator (for RFQ and trial notes)

To estimate product consumption from a target ppm:

kg/day ≈ (Target ppm) × (Solution flow, m³/day) ÷ 1,000 ÷ (Active fraction)
Example: 10 ppm at 20,000 m³/day with 50% active → 10 × 20,000 ÷ 1,000 ÷ 0.50 = 400 kg/day

Use this only for planning and procurement. Field performance determines the final dose and economics.

Trial protocol (lab → field) you can actually run

A good wetting-agent trial isolates distribution effects from other variables. The goal is to prove hydraulic improvement and metallurgical benefit without introducing downstream problems.

Phase 1: Compatibility & screening (1–3 days)

Jar/bench mix: prepare solutions in site water at proposed ppm steps; check clarity, separation, odor, and stability over 24 hours.
Foam check: simple agitation test in a cylinder; note foam height and collapse time.
Materials check: confirm compatibility with common elastomers/plastics used in dosing systems and hoses.

Phase 2: Column test (optional but strong evidence)

Compare control vs treated: same ore, same application rate, same solution chemistry.
Track: percolation rate, moisture distribution (if measurable), solution grade trends, and reagent consumption.
Watch-outs: fines migration changes and any unusual turbidity increase.

Phase 3: Field trial on a defined section/cell (2–6 weeks)

Control area: maintain an untreated section under as similar operating conditions as possible.
Ramp strategy: step dose upward only if foam and downstream signals remain acceptable.
KPIs: ponding frequency, infiltration response, application uptime, solution grade stability, and overall recovery rate.
Decision gate: continue/stop criteria agreed in advance (EHS + operations + metallurgy + procurement).

Monitoring signals (what to track weekly)

Keep monitoring simple: choose 2–3 primary signals and 2 secondary checks. This avoids “data overload” while still catching issues early.

Primary signals

Ponding and infiltration: number of ponding events, time-to-drain, and observed wetting pattern.
Irrigation stability: pressure/flow variability, emitter clogging frequency, and uptime.
Metallurgical response: solution grade trend and recovery rate relative to control.

Secondary checks

Foam behavior: sumps/ponds/pipelines (especially after dosing changes).
Return solution clarity/turbidity: potential fines movement changes.
Reagent consumption: ensure changes aren’t driven by unrelated chemistry shifts.
Scaling tendency: any increase in deposits in lines, emitters, or distribution components.

Specification & acceptance checks (procurement-ready)

When comparing wetting agents, ask for data you can document and verify at receipt. A strong supplier response includes:

Commercial identity (must-have)

Product identity: product name, grade, manufacturer, and intended application (heap leach wetting).
Traceability: batch/lot number, manufacturing date, and shelf-life statement.
Documentation: current SDS and typical COA template.

Typical COA items (recommended)

Active content / assay: wt% active (or solids) with method reference.
Density and viscosity: for dosing system calibration and pump selection.
pH (as supplied): indicator of product handling and compatibility notes.
Appearance: color/clarity; define acceptable variability.
Cloud point / pour point: especially important for cold-weather sites.
Foam tendency (if available): even a simple comparative test can help screen candidates.

Packaging & logistics (what buyers need)

Packaging options: drums / IBC / bulk; liner type, venting, and closure details.
Storage: temperature range, agitation requirement (if any), freeze/thaw guidance.
Supply: lead times, minimum order quantities, Incoterms, and recurring supply plan.

Handling & storage (EHS-first)

Store sealed: in original packaging, protected from extreme temperatures and direct sunlight.
Secondary containment: bunding for drums/IBCs; clear labels in dosing areas.
Transfer controls: verify hose and seal compatibility; keep spill kits and eyewash access near transfer points.
PPE baseline: follow SDS; eye protection and chemical-resistant gloves are common minimums.
Mixing: add to a well-mixed zone to avoid localized over-concentration and foaming.

Troubleshooting: symptoms → likely causes → first checks

Symptom	Likely cause	First checks
Ponding increases after dosing	Overdosing, foam/air entrainment, or distribution imbalance	Reduce dose step, check foam collapse time, confirm injection point mixing
No measurable improvement	Distribution not the limiting factor, or product not compatible with site water	Verify solution surface tension trend (if measured), check stability in site water, review irrigation uniformity
Foam in ponds/sumps	Formulation too foamy for the system or mechanical aeration	Switch to low-foam grade, reduce turbulence at injection, add defoamer only if approved
Higher turbidity in PLS/return	Fines mobilization changes	Track turbidity trend vs dose steps, confirm no equipment upset, consider dose reduction or different chemistry
Emitter/clogging changes	Scaling tendency or solids carryover, not necessarily the wetting agent	Check scaling indices, inspect filters, review water chemistry and solids loading

If you share your heap configuration and a small data set (dose steps, ponding events, pressure/flow, and recovery trend), we can help interpret whether the response is hydraulic, metallurgical, or driven by another variable.

RFQ notes (what to include for a fast, accurate quote)

Leach type: acid / cyanide / other; typical pH and temperature range.
Water quality: recycle ratio, conductivity/TDS, hardness, sulfate/chloride (if available).
Application method: drip/sprinkler, flow rate (m³/h or m³/day), number of cells/pads, and irrigation cycle strategy.
Constraints: foam sensitivity, biodegradability preference, downstream circuit sensitivities.
Trial plan: desired timeframe, control area availability, and target KPIs.
Volumes: estimated monthly consumption at screening ppm, plus packaging preference (IBC/drum/bulk).
Delivery: country/city, Incoterms, and any documentation requirements (SDS/COA/statement of compliance).

Need a compliant alternative or trial support?

Send your constraints and target performance. We’ll propose options with SDS/COA expectations, dosing guidance for your flow rate, and a trial checklist your operations team can execute.

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FAQ (quick answers for buyers and operations)

Will a wetting agent always increase recovery?

Not always. The best results occur when recovery is limited by solution distribution rather than reaction kinetics. A controlled trial with a defined control area is the most reliable way to confirm value.

Can wetting agents cause problems downstream?

They can if the formulation is not matched to the circuit (foam, phase separation sensitivity, adsorption interactions, etc.). This is why compatibility checks and stepwise dose ramps are recommended.

What’s the “best” ppm?

There is no universal best dose. Sites often start with conservative screening ppm and adjust based on infiltration, foam response, and metallurgical KPIs. Final dosing is site- and product-specific.

Educational content only. Always follow site EHS rules and the supplier SDS for safe use. Any dosing figures shown are planning estimates and must be validated with site trials and approvals.