At first glance, water might seem like the simplest ingredient in a gold elution plant, just something to fill the tanks and carry the heat. But if you’ve ever struggled with inconsistent results, long elution times, or dull electrowinning plates, chances are the culprit wasn’t your system design.
It was your water quality.
In gold elution, the chemistry is delicate. Even trace minerals or impurities can interfere with how gold desorbs from carbon. And in Zimbabwe, where borehole water and municipal supply vary drastically from place to place, water quality can make or break recovery efficiency.
Let’s break down why that happens and what to do about it.
1. The Role of Water in Elution Chemistry
Water is the backbone of your elution solution, the medium that carries caustic soda, cyanide, and heat through the carbon columns.
During the process, gold ions are stripped off the carbon and dissolved into the hot solution. That reaction depends on:
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Temperature stability
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pH levels
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Ion balance (especially sodium, calcium, and magnesium)
If the water has unwanted minerals, salts, or suspended solids, it alters that chemistry. Suddenly, what should be a clean, consistent process starts showing odd variations, lower gold loading, longer elution cycles, or uneven electrowinning deposits.
If you’d like a quick overview of how the elution stage actually works, here’s a complete breakdown: How the Elution Process Works: From Loaded Carbon to Pure Gold.
2. Common Water Quality Problems in Zimbabwean Mines
Here’s what we’ve seen in over two decades of testing and operating gold elution systems across Bulawayo, Filabusi, Kadoma, and Gwanda:
a. High Hardness (Calcium & Magnesium)
Hard water binds with cyanide and caustic soda, forming unwanted precipitates that can clog valves and coat carbon surfaces. This slows elution and reduces efficiency.
b. Iron and Manganese Contamination
Even low levels of iron can react with cyanide, creating ferrocyanide complexes that reduce free cyanide concentration. The result? Poor gold stripping.
c. Suspended Solids
Dust, silt, or organic matter from boreholes can block heat exchangers, nozzles, and electrowinning cells. These deposits insulate heat transfer surfaces and raise energy consumption.
d. pH Instability
Some borehole water in Zimbabwe has natural acidity. Without correction, it can neutralize your caustic, drop the pH, and ruin stripping conditions.
Depending on whether you’re running a ZADRA or AARL system, water hardness can impact the elution cycle differently. You can compare both systems here: ZADRA vs AARL: Which Gold Elution System Performs Better in Zimbabwe.
3. The Hidden Costs of Poor Water Quality
Most operators only look at chemical costs and stripping time. But poor water quality creates hidden losses:
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Reduced carbon lifespan: scaling and fouling weaken adsorption sites.
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Higher energy use: as buildup on heat exchangers forces heaters to work harder.
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Inconsistent gold purity: impurities carry through to electrowinning.
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Longer plant downtime: more maintenance, more chemical cleaning, less production.
These issues often build up slowly, a 2-hour delay here, a 5% drop in efficiency there, until your plant is losing kilograms per month without anyone noticing.
4. How to Improve Water Quality in Gold Elution Plants
The good news? Most water issues can be corrected with a few practical adjustments:
✅ Test Your Water Regularly
Start with a full chemical analysis every few months. Track total hardness, TDS, iron, and manganese.
✅ Install a Basic Filtration System
Even a simple sand filter or cartridge system before your water enters the circuit can make a big difference.
✅ Consider Water Softening or Reverse Osmosis (RO)
For plants using borehole water with high hardness or iron, a compact RO system can drastically improve elution performance.
✅ Maintain pH and Cyanide Levels
Always check that the final solution entering the elution column has the correct pH (usually above 12) and cyanide concentration (around 0.1–0.2%).
If you’d like to revisit why elution is such a vital step in the entire gold recovery chain, read our introduction: What Is Gold Elution and Why It’s the Heart of Gold Recovery.
5. Why Bulawayo Elutions Tests Every Drop
At Bulawayo Elutions, we test all incoming water for hardness, iron content, and pH before it ever reaches your system.
We adjust the chemistry for your local supply, whether it’s municipal, borehole, or dam water, ensuring your elution performs exactly as designed.
That’s one of the reasons clients from Gwanda to Mazowe trust us to optimize their elution cycles, not just install them.
