Common antimony salts and compounds in water: solubility and treatment
Antimony in natural and industrial waters is usually discussed by its dissolved species and by antimony-bearing solids, rather than as a set of unchanged salt molecules. Solubility values below describe reported properties of selected pure compounds; they do not predict the dissolved antimony concentration in a natural or process water.
Selected antimony compounds and reported water solubility
Values are approximate reported data for individual compounds. Conditions and methods differ, and some entries are estimates or read-across values. pH, oxidation state, hydrolysis, complexing ions and solids can change the amount and form of antimony in an actual water sample.
| Compound | Formula / form | Reported water solubility | Relevance in water and treatment |
|---|---|---|---|
| Antimony trioxide | Sb2O3, Sb(III) | About 3.3 mg/L at 22.2 °C in one reported data set; pH-dependent values vary | Low-solubility oxide used in products and found in industrial residues. A particle-bearing sample may contain more total Sb than dissolved Sb. |
| Antimony trisulfide (stibnite) | Sb2S3, Sb(III) | About 1.75 mg/L (reported) | Important antimony ore mineral. Oxidation and weathering of mine waste can mobilize antimony beyond what the solid’s simple water-solubility value suggests. |
| Antimony pentoxide | Sb2O5, Sb(V) | 594 mg/L (read-across estimate in a government assessment) | Reported value is not a direct measured equilibrium value for every form or pH; antimonate speciation is more useful for assessing treatment. |
| Antimony trichloride | SbCl3, Sb(III) | 100,000 mg/L reported as apparent solubility; reacts with water | Hydrolyses in water, so the starting salt does not remain as intact SbCl3. It is a reactive soluble source, not a representative stable salt in most natural waters. |
| Sodium hexahydroxoantimonate | NaSb(OH)6, Sb(V) | 594 mg/L (reported read-across / moderate-solubility value) | Soluble antimonate source. In water, Sb(V) is commonly present as hydroxoantimonate species. |
| Potassium antimony tartrate | Antimony(III)-tartrate complex; hydrate form may vary | 830,000 mg/L reported | Highly water-soluble compound used as an antimony source in specific applications; tartrate complexation means its aqueous behaviour differs from simple inorganic salts. |
The table is a comparison of selected compounds, not a list of all antimony species in water. Near neutral pH, dissolved Sb(III) is often largely present as Sb(OH)3, while Sb(V) commonly occurs as Sb(OH)6−. Concentration and speciation in real waters depend on redox conditions, pH, dissolved organic matter, sulfide, mineral surfaces and competing constituents.
Removal, purification and recovery options
Select a process based on whether antimony is dissolved or particle-bound, its oxidation state, concentration, salinity, competing ions, and the required water quality. Antimony removal generally transfers it to a solid, spent medium, regenerant or membrane concentrate; those residual streams need appropriate management.
- Coagulation and co-precipitation: ferric coagulants can capture dissolved antimony in floc. Sb(V) removal often benefits from acidic pH conditions; performance varies with dose, pH, Sb species and competing ions.
- Adsorption: iron- or titanium-based media and other engineered adsorbents can remove antimony, particularly for polishing. Media selection and service life depend on the water matrix and require breakthrough testing.
- Oxidation followed by capture: oxidation can convert Sb(III) to Sb(V) to improve performance in a downstream process selected for that species. Oxidation alone does not remove antimony.
- Ion exchange: anion-exchange resins may capture anionic Sb(V) species. Neutral Sb(III) and competing anions can limit performance, so speciation and pilot or bench testing matter.
- Nanofiltration or reverse osmosis: membranes can reduce dissolved antimony in suitable waters, while concentrating it in the reject stream. Evaluate pressure, fouling, scaling, recovery and concentrate disposal.
- Precipitation in process waters: iron-, calcium- or sulfide-based precipitation may be considered for some concentrated industrial streams. The chemistry, residual solids and downstream disposal or recovery must be assessed for the specific stream.
There is no universal removal technology based on a compound’s pure-water solubility alone. Use a representative sample and verify treatment performance under the expected operating range before design.
Discuss an antimony-treatment challenge
Share the water composition and treatment objective with Lenntech to discuss suitable separation, purification or recovery options.
Discuss a water-treatment challenge
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Last reviewed: 8 November 2026 by Lenntech.
Sources and further reading
- Environment and Climate Change Canada: Screening assessment — antimony-containing substances (physical and chemical properties).
- National Toxicology Program: Antimony trioxide — physical properties and water solubility.
- Health Canada: Antimony in drinking water — speciation and treatment.
- U.S. EPA: Overview of drinking-water treatment technologies.
- USGS: Antimony in mine wastes — geochemistry, mineralogy, and mobility.