Antimony (Sb) in Water Treatment
Quick Answer
Antimony (Sb) is a metalloid with atomic number 51. PubChem lists its standard state as solid and its relative atomic mass as 121.760.
Antimony can occur near mining, smelting, flame-retardant and metal-processing activities. Oxidation state affects adsorption and mobility; iron-based adsorption, coagulation, ion exchange or membranes may be evaluated after speciation.
Interesting Facts
- Antimony’s symbol Sb comes from its Latin name, stibium.
- Antimony compounds are used in flame-retardant systems and metal alloys, so industrial source history can matter more than geology alone.
- Sb(III) and Sb(V) do not behave identically in water; a total-antimony number can hide the treatment-relevant chemistry.
Water-treatment Design Implications
An element name alone is not enough to select treatment equipment. Confirm chemical form or speciation, total and dissolved concentration, pH, alkalinity, competing ions and the product-water target. Send the water-analysis results to Watermart to identify additional testing and shortlist processes before equipment is specified.
Summary Data Sources
- PubChem — Antimony
- IUPAC Periodic Table of Elements
- WHO chemical hazards in drinking-water
- WHO — Chemical fact sheet: Antimony
- US EPA — Overview of drinking-water treatment technologies
Practical Reference: Antimony in Water
1. Basic Information
| Atomic Number | 51 |
| Symbol | Sb |
| Relative Atomic Mass | 121.760 |
| Element Group | Metalloid |
| Important Aqueous Forms | Sb(III) and Sb(V) |
2. How Can Antimony Enter Water?
Antimony can come from weathering of sulfide minerals, mining and smelting, metal manufacturing, flame-retardant materials, and certain industrial waste streams. It is also used in alloys and as a catalyst in some polymer production. Site history and material use are therefore often more informative than assuming antimony is a routine natural contaminant.
A “total antimony” result includes dissolved and particulate fractions. Comparing filtered and unfiltered samples can help establish whether the main problem is separable solids or dissolved species that need a chemical process.
3. Why Does Speciation Matter?
In water, antimony is not normally free Sb metal. Sb(III) and Sb(V) species have different charge, mobility, toxicology, and adsorption affinity. pH, redox conditions, sulfide, dissolved organic matter, and mineral surfaces all influence which forms dominate.
Oxidising Sb(III) to Sb(V) may be part of a treatment train, but it does not automatically improve removal on every medium or coagulant. Research shows that the two species’ affinity for iron oxides changes with pH and media properties. Jar or column testing with the actual water is therefore more reliable than a rule that “Sb(V) is always easier”.
4. Processes Worth Testing
- Coagulation and filtration: iron salts may capture or co-precipitate some antimony species. Dose, pH, mixing, and floc separation need testing.
- Adsorptive media: iron-, aluminium-, titanium-, or zirconium-based media may be considered. Capacity depends on antimony valence, pH, phosphate, silica, and competing ions.
- Ion exchange: may be useful where antimony species have the appropriate charge and the water matrix supports resin selectivity.
- Nanofiltration or reverse osmosis: can separate many dissolved species, but actual rejection, recovery, scaling, and concentrate management must be verified.
- Combined oxidation and separation: should be selected only when testing shows that the speciation change benefits the downstream process.
Ordinary activated carbon and sediment cartridges should not be promised as universal solutions for dissolved antimony. A sediment filter only helps when antimony is carried on particles.
5. Minimum Data before Equipment Selection
Request total and dissolved antimony, pH, alkalinity, ORP or other redox context, turbidity/TSS, iron, manganese, sulfate or sulfide, phosphate, silica, and dissolved organic matter where relevant. Confirm the analytical method and reporting limit; Sb(III)/Sb(V) speciation requires appropriate methods and sample preservation.
Compare results with current requirements for the location and intended use. If a guideline number is stated, link directly to the regulator and date the source rather than copying an old value without jurisdictional context.
6. Residuals and Sustainability
Treatment does not destroy antimony; it transfers it to sludge, spent media, regenerant, or membrane concentrate. Leach testing, waste classification, worker safety, and a disposal or recovery route belong in the design from the start.