Common strontium salts in aqueous solutions: solubility and treatment technologies
In natural waters, dissolved strontium is present mainly as the divalent ion Sr2+. Names such as strontium sulfate or strontium chloride describe minerals, reagents or solids that may form; dissolved salts dissociate into ions. Concentrations vary with geology, salinity and treatment history. Seawater contains about 8 mg/L total strontium, not 8 mg/L of strontium chloride.
Common strontium-bearing salts and compounds
| Compound or mineral | Where it may occur | Solubility and treatment relevance |
|---|---|---|
| Strontium sulfate (SrSO4; celestite/celestine) | A natural mineral; may form scale where sulfate-rich water is concentrated | Sparingly soluble: about 0.135 g/L in pure water at 25 °C (reported as 0.0135 g/100 mL). High Sr2+ and sulfate concentrations can cause precipitation and scaling. |
| Strontium carbonate (SrCO3; strontianite) | A natural mineral and an industrial product made from celestite | Very slightly soluble in water. Dissolved carbon dioxide and pH affect its solubility; published reference values differ, so a single figure should not be used without checking the source and conditions. Carbonate precipitation can transfer dissolved strontium to a solid. |
| Strontium chloride (SrCl2) | Soluble reagent; may be relevant to chloride-rich process liquors and brines | Highly soluble. In water it dissociates into Sr2+ and Cl−; temperature and other dissolved salts affect saturation. |
| Strontium nitrate [Sr(NO3)2] | Soluble specialty chemical, including use in pyrotechnic compositions; may be relevant to process or wash waters where used | Soluble in water. It contributes Sr2+ and nitrate ions; treatment is selected for the full water matrix, not the nominal salt alone. |
| Strontium phosphate phases | Potential solids in phosphate-containing treatment or process streams | Several phases are possible. Formation depends on pH, phosphate speciation and competing ions; confirm with analysis and testing. |
Solubility figures are reference values for pure water at a stated temperature, not design limits for mixed brines. pH, temperature, ionic strength and co-existing ions can change precipitation behavior.
Natural waters, industrial streams and mineral processing
Weathering of strontium-bearing rocks contributes Sr2+ to groundwater and surface water. Groundwater concentrations vary with aquifer geology and contact time; seawater averages about 8 mg/L strontium. Industrial sources can include mining and mineral processing, manufacturing and concentrated process waters. Stable strontium and radioactive isotopes such as strontium-90 require different assessment; total strontium analysis does not establish isotope-specific radioactivity.
The principal commercial strontium minerals are celestite (SrSO4) and strontianite (SrCO3). Ore beneficiation may use sizing, gravity separation or flotation. Celestite can be converted chemically using a carbonate reagent to produce strontium carbonate; the route depends on mineralogy, impurities and product requirements.
Removal, purification and concentration options
Process selection depends on whether the objective is drinking-water removal, industrial reuse, brine concentration or resource recovery. Health Canada identifies chemical precipitation and ion exchange among the principal methods for naturally occurring strontium in drinking water; reverse osmosis is also used. Performance depends on the feed water.
| Technology | Potential role | Key considerations |
|---|---|---|
| Ion exchange | Cation-exchange media capture dissolved Sr2+ for removal or concentration | Calcium and magnesium compete for capacity. Assess resin selection, regeneration and regenerant disposal for the actual stream. |
| Precipitation and softening | Carbonate, sulfate or phosphate chemistry can form a strontium-bearing solid; lime softening may remove some Sr alongside hardness | Removal depends on pH, alkalinity, competing ions, reagent dose and solids separation. Sludge is produced; verify performance with testing. |
| Nanofiltration or reverse osmosis | Reduce dissolved strontium in product water and concentrate it in a reject stream | Account for recovery, energy, concentrate management and scaling risk, particularly where sulfate is present. Membranes transfer strontium; they do not destroy it. |
| Selective sorption | Specialized inorganic media can capture strontium in polishing or targeted treatment | Capacity and selectivity depend on competing ions; plan for media regeneration or disposal. |
Recovery from concentrated brine is different from producing compliant water. A 2026 study investigated sequential oxalate precipitation and ion exchange to separate strontium from seawater reverse-osmosis brine. This is a reported process-development approach, not a guarantee of economic recovery from every brine.
For process selection, characterize total and dissolved strontium, calcium, magnesium, sulfate, carbonate alkalinity, chloride, pH, temperature and total dissolved solids. Bench or pilot tests can assess removal, selectivity, scaling, residuals and recovered-product quality. Lenntech's ion-exchange systems and reverse osmosis may form part of a treatment train.
Sources and further reading
- Health Canada: Strontium in drinking water — technical document
- PubChem / ILO-WHO: Strontium sulfate properties and solubility
- PubChem / HSDB: Strontium carbonate properties and solubility
- U.S. Geological Survey: Strontium statistics and information
- Mesa et al. (2025): Strontium minerals as critical raw materials — processing and beneficiation
- Papadopoulou et al. (2025): Strontium recovery and elimination strategies
- Sequential precipitation and ion exchange for strontium recovery from seawater RO brine (2026)