ANTIMONY TRIOXIDE

ANTIMONY TRIOXIDE

Antimony(III) oxide is the inorganic compound with the formula Sb2O3. Antimony trioxide is the most important commercial compound of antimony. Antimony trioxide is found in nature as the minerals valentinite and senarmontite. Like most polymeric oxides, Sb2O3 dissolves in aqueous solutions with hydrolysis. A mixed arsenic-antimony oxide occurs in the nature as the very rare mineral stibioclaudetite.

CAS No. : 1309-64-4
EC No. : 215-474-6

Synonyms:
Antimony(III) oxide; Antimony sesquioxide; Antimonous oxide; Flowers of Antimony; antımony(III) oxıde; antimoni trioksit; antimoni trioksid; antimonitrioksit; antimonytrioxide; ato; Antimony Oxide; Antimony Trioxide; Dioxodistiboxane; Stibine oxide; triphenyl; Dioxodistiboxane; Antimony sesquioxide; Antimony White; Stibine oxide; triphenyl-; hydrate; Diantimony trioxide; Flowers of antimony; Triphenylantimony oxide; Oxo-oxostibanyloxystibane; Di(phenyl)stiborylbenzene; Triphenylstibine oxide; Antimony(III) oxide; Antimonous oxide; MFCD00011214; n-propylnitrate; SO3b2; Antimony(III) oxide, CP; Antimony Trioxide Nanopowder; ANTIMONY TRIOXIDE; Antimony Trioxide; Antimony(III) oxide, >=99%; Antimony(III) oxide, 99.5%; Antimony(III) oxide, elec. gr.; 8927AF; Antimony(III) oxide, puriss. p.a.; AKOS015904094; Antimony Oxide Nanoparticle Dispersion; Antimony(III) oxide, 99.99% trace metals basis; Antimony(III) oxide, 99.999% trace metals basis; J-520229; Antimony Trioxide; Antimony(III) oxide, powder, 5 mum, ReagentPlus(R), 99%; Antimony trioxide, United States Pharmacopeia (USP) Reference Standard; Antimony(III) oxide, nanopowder, <250 nm particle size (TEM), >=99.9% trace metals basis; Triphenylantimony oxide; ATO; Antimonio triossido; Antimony Trioxide; Antimony Trioxide TMS®-HP; Diantimony trioxide; Timonox® Blue Star; antimony trioxide; diantimony Trioxide; diantimony trioxide; DI-ANTIMONY TRIOXIDE; ANTIMON(III)OXIDE; ANTIMONY TRIOXIDE; ANTIMONY OXIDE; ANTIMONOUS OXIDE; ANTIMONY(+3)OXIDE; SB OXIDE; a1530; antimonious oxide;  antimony sesquioxide; antimony(3+); oxygen(2-); antimony(III) oxide

Antimony Trioxide

Production and properties of Antimony Trioxide
Global production of Antimony trioxide in 2012 was 130,000 tonnes, an increase from 112,600 tonnes in 2002. China produces the largest share followed by US/Mexico, Europe, Japan and South Africa and other countries (2%).

As of 2010, Antimony trioxide was produced at four sites in EU27. It is produced via two routes, re-volatilizing of crude Antimony trioxide and by oxidation of antimony metal. Oxidation of antimony metal dominates in Europe. Several processes for the production of crude Antimony trioxide or metallic antimony from virgin material. The choice of process depends on the composition of the ore and other factors. Typical steps include mining, crushing and grinding of ore, sometimes followed by froth flotation and separation of the metal using pyrometallurgical processes (smelting or roasting) or in a few cases (e.g. when the ore is rich in precious metals) by hydrometallurgical processes. These steps do not take place in the EU but closer to the mining location.

Re-volatilizing of crude Antimony trioxide
Step 1) Crude stibnite is oxidized to crude Antimony trioxide using furnaces operating at approximately 500 to 1,000 °C. The reaction is the following:

2 Sb2S3 + 9 O2 → 2 Sb2O3 + 6 SO2
Step 2) The crude Antimony trioxide is purified by sublimation.

Oxidation of antimony metal
Antimony metal is oxidized to Antimony trioxide in furnaces. The reaction is exothermic. Antimony trioxide is formed through sublimation and recovered in bag filters. The size of the formed particles is controlled by process conditions in furnace and gas flow. The reaction can be schematically described by:
4 Sb + 3 O2 → 2 Sb2O3

Properties of Antimony Trioxide
Antimony trioxide is an amphoteric oxide, it dissolves in aqueous sodium hydroxide solution to give the meta-antimonite NaSbO2, which can be isolated as the trihydrate. Antimony trioxide also dissolves in concentrated mineral acids to give the corresponding salts, which hydrolyzes upon dilution with water. With nitric acid, the trioxide is oxidized to antimony(V) oxide.

When heated with carbon, the oxide is reduced to antimony metal. With other reducing agents such as sodium borohydride or lithium aluminium hydride, the unstable and very toxic gas stibine is produced. When heated with potassium bitartrate, a complex salt potassium antimony tartrate, KSb(OH)2•C4H2O6 is formed.

Structure of Antimony Trioxide
The structure of Sb2O3 depends on the temperature of the sample. Dimeric Sb4O6 is the high temperature (1560 °C) gas. Sb4O6 molecules are bicyclic cages, similar to the related oxide of phosphorus(III), phosphorus trioxide. The cage structure is retained in a solid that crystallizes in a cubic habit. The Sb-O distance is 197.7 pm and the O-Sb-O angle of 95.6°. This form exists in nature as the mineral senarmontite. Above 606 °C, the more stable form is orthorhombic, consisting of pairs of -Sb-O-Sb-O- chains that are linked by oxide bridges between the Sb centers. This form exists in nature as the mineral valentinite.

Uses of Antimony Trioxide
The annual consumption of Antimony trioxide in the United States and Europe is approximately 10,000 and 25,000 tonnes, respectively. The main application is as flame retardant synergist in combination with halogenated materials. The combination of the halides and the antimony is key to the flame-retardant action for polymers, helping to form less flammable chars. Such flame retardants are found in electrical apparatuses, textiles, leather, and coatings.

Other applications of Antimony Trioxide:
Antimony trioxide is an opacifying agent for glasses, ceramics and enamels.
Some specialty pigments contain antimony.
Antimony trioxide is a useful catalyst in the production of polyethylene terephthalate (PET plastic) and the vulcanization of rubber.

Safety of Antimony Trioxide
Antimony trioxide has suspected carcinogenic potential for humans. Its TLV is 0.5 mg/m3, as for most antimony compounds.
No other human health hazards were identified for Antimony trioxide, and no risks to human health and the environment were identified from the production and use of antimony trioxide in daily life.

Properties of Antimony Trioxide
Chemical formula Sb2O3
Molar mass 291.518 g/mol
Appearance white solid
Odor odorless
Density 5.2 g/cm3, α-form
5.67 g/cm3 β-form
Melting point 656 °C (1,213 °F; 929 K)
Boiling point 1,425 °C (2,597 °F; 1,698 K) (sublimes)
Solubility in water 370 ± 37 µg/L between 20.8°C and 22.9°C
Solubility soluble in acid
Magnetic susceptibility (χ) -69.4·10−6 cm3/mol
Refractive index (nD) 2.087, α-form
2.35, β-form

Antimony trioxides are used as synergists to increase the activity of halogenated flame retardants by hindering the chain reaction of the flame gas phase through stepwise release of the halogenated radicals.

Antimony trioxide (ATO) is commonly used as a co-synergist with halogenated flame retardants to enhance their effectiveness. Recent comprehensive genotoxicity studies and a critical review by the European Commission have indicated that, contrary to the indications of earlier less well authenticated studies, antimony trioxide is not a genotoxic carcinogen. No adverse health effects are expected from antimony trioxide, although there remains some uncertainty on a possible cancer hazard arising from inhalation of particles, where better data on particular exposure is required. However, in most cases, exposure is probably minor compared with exposure to antimony trioxide from other sources in the domestic and urban environment.

Brominated organic compounds and antimony trioxide traditionally used in molding compounds as flame retardants are known to have deleterious impacts on the environment. Brominated flame retardants (BFRs) are also referred to as halogenated flame retardants due to the presence of bromine (Br−), which is considered a halogen. Halogens are nonmetal elements from Group 17 in the new periodic table including fluorine, chlorine, bromine, iodine, and astatine.

The other substance of concern in conventional flame-retardant systems is antimony trioxide. Antimony trioxides are used as synergists to increase the activity of halogenated flame retardants by hindering the chain reaction of the flame gas phase through stepwise release of the halogenated radicals.

What is antimony trioxide?
Antimony trioxide is a chemical used in the manufacture of some polyethylene terephthalate (PET) plastic, which is used to make food and beverage containers.  These include ovenproof or microwavable plastic trays, as well as some plastic water bottles.
Antimony trioxide is also added to some flame retardants to make them more effective in consumer products, including upholstered furniture, textiles, carpeting, plastics, and children’s products.
As of January 2020, California has banned the sale and distribution of new upholstered furniture, replacement components of reupholstered furniture, foam in mattresses, and certain children’s products made for residential use if these products contain more than 0.1% of certain flame retardant-related chemicals, including antimony trioxide.

How does exposure to antimony trioxide occur?
Antimony trioxide can leach into food and beverages from some containers made with antimony trioxide that are exposed to high temperatures (especially above 110 °F).
Antimony trioxide can migrate into air and dust from some products made with antimony trioxide.
During pregnancy, antimony trioxide can pass from mother to baby.

This chapter reviews the physical and chemical properties, toxicokinetics, toxicological, epidemiological, and exposure data on antimony trioxide. The subcommittee used that information to characterize the health risk from exposure to antimony trioxide. The subcommittee also identified data gaps and recommended research relevant for determining the health risk from exposure to antimony trioxide.

Antimony trioxide, also known as antimony oxide or Sb2O3, is the most widely produced compound of elemental antimony. The nations that produce the most antimony trioxide are China, South Africa, Bolivia, Russia, Tajikistan, and Kyrgyzstan. Typical applications for antimony trioxide include flame retardant synergist for use in plastics, rubber, paints, paper, textiles, and electronics; polyethylene terephthalate polymerization catalyst; a clarifying agent for glass; an opacifier for porcelain and enamel; and a white pigment for paint. When used as a flame retardant, antimony trioxide is often used in combination with halogenated compounds. Antimony trioxide is used as a synergist to enhance the activity of the halogenated flame retardant. In the absence of antimony trioxide about twice as much halogenated compound would be needed to reach the same level of flame retardancy.

Antimony Trioxide is a white, odorless crystalline (sand-like) powder. It is used as a flame-proofing agent, in pigments and ceramics, to stain iron and copper, and to decolorize glass.

What is Antimony Trioxide?
Antimony trioxide is an industrial chemical and also occurs naturally in the environment.

How is Antimony Trioxide used?
In Canada, antimony trioxide is primarily used in combination with other compounds to provide flame retardant properties. Flame retardants used in household items such as mattress covers, furniture and carpets may contain antimony trioxide.
Antimony trioxide is also used in the manufacturing of a plastic material known as polyethylene terephthalate (PET).
Antimony trioxide is both manufactured in and imported into Canada.

Why did the Government of Canada assess Antimony Trioxide?
Prior to the assessment, antimony trioxide was identified as a potential concern for human health based on its classification by international organizations as a substance that was found to cause cancer in laboratory animals, and based on a high potential for exposure (not including workplace exposures) to the general population of Canada.
Antimony trioxide was also considered to be a priority for assessment of potential risks to the environment; therefore, potential environmental effects were also evaluated in this screening assessment.

How are Canadians exposed to it?
The general population is expected to be exposed to low levels of antimony trioxide from environmental media (soil, drinking water, ambient air), from food and from contact with household items such as mattress covers, furniture and carpets that may contain antimony trioxide.

How is Antimony Trioxide released to the environment?
Antimony trioxide may be released to the environment via landfills and wastewater treatment systems as a result of industrial processes and through the use and disposal of consumer products containing this substance.
Combustion of coal, non-ferrous metal production (smelters), antimony mining and abrasion of automobile brake pads are also expected to result in releases of antimony trioxide to the environment.

What are the results of the assessment?
The Government of Canada has conducted a science-based evaluation of antimony trioxide, called a screening assessment.
Screening assessments address potential for harm to the general population (not including workplace exposures) and the environment.
The Government of Canada has concluded that antimony trioxide is not harmful to the health of the general population at current levels of exposure.
Additionally, although antimony trioxide has the potential to remain in the environment for a long time, it is not expected to accumulate in organisms or cause harm to organisms; therefore, the Government of Canada has also concluded that antimony trioxide is not entering the environment in a quantity or under conditions that constitute a danger to the environment.

About Antimony trioxide
Antimony trioxide is registered under the REACH Regulation and is manufactured in and / or imported to the European Economic Area, at ≥ 10 000 tonnes per annum.

Antimony trioxide is used by consumers, in articles, by professional workers (widespread uses), in formulation or re-packing, at industrial sites and in manufacturing.

Consumer Uses of Antimony Trioxide
Antimony trioxide is used in the following products: pH regulators and water treatment products and polymers.
Other release to the environment of Antimony trioxide is likely to occur from: indoor use and outdoor use resulting in inclusion into or onto a materials (e.g. binding agent in paints and coatings or adhesives).

Article service life of Antimony Trioxide
Release to the environment of Antimony trioxide can occur from industrial use: industrial abrasion processing with low release rate (e.g. cutting of textile, cutting, machining or grinding of metal), in the production of articles, formulation of mixtures and formulation in materials. Other release to the environment of Antimony trioxide is likely to occur from: outdoor use in long-life materials with low release rate (e.g. metal, wooden and plastic construction and building materials) and indoor use in long-life materials with low release rate (e.g. flooring, furniture, toys, construction materials, curtains, foot-wear, leather products, paper and cardboard products, electronic equipment). Antimony trioxide can be found in complex articles, with no release intended: vehicles, machinery, mechanical appliances and electrical/electronic products (e.g. computers, cameras, lamps, refrigerators, washing machines) and electrical batteries and accumulators. Antimony trioxide can be found in products with material based on: fabrics, textiles and apparel (e.g. clothing, mattress, curtains or carpets, textile toys), plastic (e.g. food packaging and storage, toys, mobile phones), metal (e.g. cutlery, pots, toys, jewellery), leather (e.g. gloves, shoes, purses, furniture), stone, plaster, cement, glass or ceramic (e.g. dishes, pots/pans, food storage containers, construction and isolation material), rubber (e.g. tyres, shoes, toys), wood (e.g. floors, furniture, toys) and paper (e.g. tissues, feminine hygiene products, nappies, books, magazines, wallpaper).

Widespread uses by professional workers of Antimony Trioxide
Antimony trioxide is used in the following products: adhesives and sealants, coating products, inks and toners, polymers, textile treatment products and dyes, pH regulators and water treatment products, lubricants and greases and paper chemicals and dyes.
Antimony trioxide is used for the manufacture of: chemicals, plastic products, textile, leather or fur, wood and wood products, rubber products and mineral products (e.g. plasters, cement).
Release to the environment of Antimony trioxide can occur from industrial use: industrial abrasion processing with low release rate (e.g. cutting of textile, cutting, machining or grinding of metal).
Other release to the environment of Antimony trioxide is likely to occur from: indoor use, outdoor use resulting in inclusion into or onto a materials (e.g. binding agent in paints and coatings or adhesives), outdoor use in long-life materials with low release rate (e.g. metal, wooden and plastic construction and building materials), outdoor use in long-life materials with high release rate (e.g. tyres, treated wooden products, treated textile and fabric, brake pads in trucks or cars, sanding of buildings (bridges, facades) or vehicles (ships)) and indoor use in long-life materials with low release rate (e.g. flooring, furniture, toys, construction materials, curtains, foot-wear, leather products, paper and cardboard products, electronic equipment).

Formulation or re-packing of Antimony Trioxide
Antimony trioxide is used in the following products: polymers, coating products, laboratory chemicals and semiconductors.
Antimony trioxide has an industrial use resulting in manufacture of another substance (use of intermediates).
Release to the environment of Antimony trioxide can occur from industrial use: in the production of articles, formulation of mixtures, formulation in materials, manufacturing of the substance and as an intermediate step in further manufacturing of another substance (use of intermediates).

Uses at industrial sites of Antimony Trioxide
Antimony trioxide is used in the following products: polymers, laboratory chemicals, coating products, semiconductors, fillers, putties, plasters, modelling clay and inks and toners.
Antimony trioxide has an industrial use resulting in manufacture of another substance (use of intermediates).
Antimony trioxide is used in the following areas: formulation of mixtures and/or re-packaging and municipal supply (e.g. electricity, steam, gas, water) and sewage treatment.
Antimony trioxide is used for the manufacture of: chemicals, machinery and vehicles, plastic products, mineral products (e.g. plasters, cement), electrical, electronic and optical equipment and textile, leather or fur.
Release to the environment of Antimony trioxide can occur from industrial use: in the production of articles, as an intermediate step in further manufacturing of another substance (use of intermediates), formulation of mixtures, formulation in materials, manufacturing of the substance and as processing aid.

Manufacture of Antimony Trioxide
Release to the environment of Antimony trioxide can occur from industrial use: manufacturing of the substance, as an intermediate step in further manufacturing of another substance (use of intermediates), formulation in materials, in the production of articles and formulation of mixtures.

Antimony Trioxide is an inorganic compound with the formula Sb2O4. This material, which exists as the mineral cervantite, is white but reversibly yellows upon heating. The material, with empirical formula SbO2, is called antimony tetroxide to signify the presence of two kinds of Sb centers.

Antimony trioxide, together antimony tetroxide and antimony pentoxide, are the current three compounds forming between antimony and oxygen with industrial application. Antimony can form a series of oxide with oxygen such as Sb2O3, Sb2O4, Sb2O5, Sb6O13, and Sb2O as well as gaseous SbO. However, only the first three compounds have significance in industrial production with other oxides mostly being the transition product of various kinds of antimony production process.

Antimony trioxide (Sb2O3, Mr291.50) is a dual-type substance including cubic crystal and monoclinic crystal type. For different crystal form, the density and refractive index also slightly differ. The density and refractive index of cubic crystal is 5.2 and 2.087, respectively while is 5.67 and 2.18 for the monoclinic crystal, respectively. The Sb2O3 commonly derived from hydrolysis of SbCl3 is rhombic crystal can burn to red heat in an inert gas or in vacuum and can generate square crystal upon sublimation. Antimony trioxide is a kind of white powder with the density being 5.67g/cm3. It becomes yellow when being heated and turn back to white upon being cooled. Upon 656 ℃, it can be molten into yellow or gray liquid with becoming white asbestos-like mercerizing substance. Antimony trioxide is slightly soluble in water, ethanol and dilute acid, easily soluble in concentrated hydrochloric acid, oxalic acid and tartaric acid, and is also soluble in fuming nitric acid and fuming sulfuric acid; it form antimonite upon be dissolved in alkali. Antimony trioxide has a low toxicity but has irritation effect on nose, eyes, throat and respiratory tract. Skin contact may induce dermatitis. Antimony trioxide mainly has two preparation methods including dry and wet. Dry method is through reducing the crude sulfur trioxide generated from the calcined sulfantimonide ore into metallic antimony in the presence of coke with soda as the melting promoting agent. The wet method is through leaching sulfur antimony ore with hydrochloric acid to generate antimony trichloride and further hydrolysis with caustic soda to obtain it.

Antimony trioxide is a widely used flame retardant suitable to being used for polyethylene, polystyrene, polyvinyl chloride, polyester, epoxy resin, polyurethane and other plastics. However, it has low flame retardant effect when being used alone. Instead it has good synergistic effect when being used in combination with phosphates, chlorine-containing compounds (such as chlorinated paraffins, PCBs, perchloro-glutar-cyclodecane etc.), bromine-containing compounds (such as Hexabromobiphenyl, Hexabromobenzene) with the flame retardant performance being improved significantly. Combining of antimony trioxide with chloride or bromide can result in antimony trichloride or antimony bromide which is reactive and volatile substances which can promote the halogen movement and generation of carbides in its solid form as well as capturing free radicals in its gas form. These reactions can all contribute to flame retardancy. It is always combined with zinc oxide, sodium hydroxide, etc. to be used as brominated synergist flame retardant synergist for being applied to plastic fire prevention system. Antimony trioxide can also be used in the manufacture of antimony potassium tartrate, pigments, porcelain enamels, dyes and other media. It can also be used as a catalyst for polyester poly-condensation.

Add the ammonia into the boiling liquid of antimony potassium (one part of antimony potassium tartrate K (SbO) C4H4O6 is dissolved in 10 parts of water); boil for a period of time, filtered, wash to give antimony trioxide.
Among them, only trace amounts of silicon, magnesium has been detected from the antimony trioxide generated from the hydrolysis method through spectroscopy qualitative analysis. It is suitable as spectral analysis standard.
Add 15 g of analytic purity grade antimony trioxide to the 500 mL beaker, further add 30ml of high purity hydrochloric acid (1 + 1), and dissolve it under stirring. Filter the solution with washed sand glass funnel to remove insoluble impurities. Further dilute it to 400 mL with high purity water when white chlorine oxide antimony is precipitated. Once the solution becomes clear, decant the supernatant liquid and wash the precipitate through decantation for several times. To the washed precipitate, add 200 mL of high-purity ammonia (1 + 25) and boil for 5~10min, when the antimony oxychloride all becomes antimony trioxide. The generated antimony trioxide particle is much smaller than the antimony oxychloride. Pour out the clearing solution and boil again for several times using the same method in dilute ammonia. Check the washed solution with silver nitrate; when the poured liquid no longer contains chlorine ions, all the antimony oxychloride has been completely converted to antimony trioxide. Then use high-purity water decantation for wash the precipitate for several times. Use Buchner funnel for filtration and then wash the precipitate with high purity water until the washed liquid becomes neutral again. The washed precipitate is dried in an oven at 150 ℃ to constant weight; take it out after cooling to get the final product of antimony trioxide.

Preparation    
Antimony trioxide is obtained by roasting stibnite:
2 Sb2S3 + 9 O2 → 2Sb2O3 + 6SO2
Temperature and air feed is carefully controlled in the process to suppress any formation of antimony tetroxide (Sb2O4). Antimony trioxide is separated from any arsenic trioxide (As2O3) that may be present as an impurity by volatilization, as the latter is much more volatile than the former. It may be also prepared by alkaline hydrolysis of antimony trichloride and subsequent dehydration of hydrous oxide under controlled heating (rapid or vigorous heating may partially oxidize Sb(III) to Sb(V).
Antimony trioxide also may be made by heating the metallic element with oxygen or air. The volatilizing trioxide is condensed and collected.

General Description    
Diantimony trioxide is a white crystalline solid. Diantimony trioxide is insoluble in water. The primary hazard is the threat to the environment. Immediate steps should be taken to limit its spread to the environment. Diantimony trioxide is used to fireproof fabrics, paper and plastics, as a paint pigment and for many other uses.