Common Cadmium Salts in Water: Solubility and Removal
Cadmium in water can originate from salts that dissolve to release cadmium ions and associated ions. In this context, “common salts in water” also includes sparingly soluble cadmium solids relevant to precipitation and removal. Dissolved cadmium is commonly present as Cd2+ in fresh water, but its behavior depends on temperature, pH, ionic strength, hydrate form and the concentrations of ligands such as chloride, sulfate and carbonate.
Common cadmium salts and aqueous behavior
The values below are indicative, phase-specific figures reported by ATSDR for the named compounds at 20°C. They are not treatment design values; reported solubilities can vary with hydrate form and experimental conditions.
| Compound/salt | Formula | Indicative solubility/aqueous behavior | Typical streams or treatment relevance |
|---|---|---|---|
| Cadmium chloride | CdCl2 | Highly soluble; ATSDR reports 1,680,000 mg/L at 20°C. | Relevant to chloride-containing process waters; chloride complexes become more important at high chloride concentrations. |
| Cadmium sulfate | CdSO4 | Soluble; ATSDR reports 608,000 mg/L at 20°C. | Relevant to sulfate-containing industrial waters; sulfate complexation depends on the water matrix. |
| Cadmium nitrate | Cd(NO3)2 | Soluble; can contribute dissolved cadmium. | Relevant where nitrate-containing cadmium salts enter a process stream. |
| Cadmium carbonate | CdCO3 | Sparingly soluble; precipitation depends on pH and carbonate availability. | May form during carbonate-based treatment when water chemistry is suitable. |
| Cadmium sulfide | CdS | Poorly soluble; ATSDR reports 1.3 mg/L at 20°C. | Sulfide precipitation can transfer dissolved cadmium to solids when conditions are suitable. |
| Cadmium hydroxide | Cd(OH)2 | Sparingly soluble solid that forms only under appropriate chemistry. | Relevant to alkaline precipitation, not a reliable assumption at ordinary water pH. |
| Cadmium phosphate | Cd3(PO4)2 | Sparingly soluble solid that forms only under appropriate chemistry. | Potential precipitate where phosphate and other conditions favor its formation. |
Implications for cadmium removal
Salt identity alone does not determine dissolved cadmium concentration in a treatment stream. Chloride and sulfate complexes can become more relevant as ligand concentrations increase. Carbonate precipitation changes with pH and alkalinity, while competing ions and other ligands can alter speciation and the performance of a removal process.
Chemical precipitation, followed by coagulation-flocculation and filtration, can separate cadmium-bearing solids from water when the selected reagents and operating conditions promote solid formation. Options include pH adjustment or lime softening, carbonate precipitation and sulfide precipitation, depending on the water matrix. Hydroxide precipitation should not be assumed to work at ordinary pH: U.S. EPA notes that Cd(OH)2 precipitation generally requires a pH of about 10–11 at elevated cadmium concentrations. Adsorption or co-precipitation may also be applicable under suitable conditions. Ion exchange and reverse osmosis are options for dissolved-cadmium removal or water polishing, including drinking-water applications, subject to feed-water composition and residuals management.
Process selection and residuals
Testing with representative water helps establish cadmium speciation, achievable removal and the behavior of competing constituents. Precipitation produces solids requiring appropriate handling; ion exchange and membrane treatment generate cadmium-containing residual streams that must also be considered. Where recovery is evaluated, its feasibility depends on the composition and quantity of the resulting solids or concentrates.
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Lenntech can assess treatment options for a specific water composition and cadmium-removal objective.
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Last reviewed: 8 November 2026 by Lenntech.
Sources and further reading
- ATSDR, Toxicological Profile for Cadmium, chapter 6 (NCBI Bookshelf)
- U.S. EPA, Ambient Water Quality Criteria for Cadmium
- Health Canada, Guidelines for Canadian Drinking Water Quality: Guideline Technical Document—Cadmium
- Australian Industrial Chemicals Introduction Scheme, Water soluble cadmium(2+) salts: Environment tier II assessment