Kingsfield Inc.

Na3T 15% Aqueous Solution for Heavy Metal Precipitation

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Many chemical production processes require the use of heavy metals. Waste waters and exhaust gasses produced by these processes contain varying amounts of heavy metals. As these are toxic, legislation limits emissions into the environment.

Heavy metals may be precipitated from aqueous solutions with sodium or calcium hydroxide. However, levels remaining after treatment are often exceeding legal limits, especially if the waste water stream contains complexing agents. Even chloride or ammonia may form complexes with e.g. mercury, thus preventing sufficient precipitation by sodium or calcium hydroxide.

Heavy metals remaining in a waste water stream after treatment with hydroxide may be precipitated by adding an inorganic or organic sulphide. However, such sulphides have a very unpleasant smell and are toxic.

Na3T, being the trisodium salt of trimercapto-s-triazine, is an exception. It is practically odourless and has a very low toxicity towards aquatic and terrestrial organisms.

Na3T reacts with heavy metals to form stable, almost insoluble heavy metal-Na3T compounds. They can be easily separated by decantation or filtration, usually after addition of a flocculating agent and disposed in a landfill as the compounds formed are insoluble in percolating rain water. Alternatively, the solids may also be subjected to calcination in order to recover the metals.

Applications

Na3T can be used to precipitate monovalent and bivalent metal ions, e.g. mercury, cadmium, silver, lead, copper, nickel, and tin. It is applied in the chemical, metal, and mining industries, as well as in waste incinerators and coal fired power stations.

Na3T is sold as a ready to use aqueous solution with a 15% content of trimercapto-s-triazine trisodium salt.

Examples of Applications

a) Incinerator flue gas wash water

Acidic wash water from a flue gas scrubber containing 9 g/L chloride, 5 mg/L mercury and 0.5 mg/L cadmium is mixed with lime milk. The pH is adjusted to approximately 8. A precipitate of calcium carbonate and metal hydroxides is formed. Per m3 of suspension 50 ml Na3T solution (15%) and 1 L of a 5% flocculant solution (Becofloc 7) are added. The precipitate is separated in a filter press. The filtrate contains <0.1 mg/L mercury and 0.13 mg/L cadmium.

b) Photo Lab Effluent Mixture

20 L of a photo lab effluent mixture containing 2.5 g/L silver is mixed with 300 ml Na3T solution (15%). After stirring for 10 minutes,

2 L of a 400 mg/L solution of flocculant (acryloyloxethyl trimethyl ammonium chloride, AETAC) are added. Gentle agitation is continued for another 10 minutes to allow formation of agglomerates. The solution is filtered. The filtrate contains approx 0.3 mg/L residual silver.

Synonyms	2,4,6-Trimercapto-s-triazine, trisodium salt Trithio cyanuric acid, trisodium salt s-Triazine-2,4,6-trithiol
Chemical formula	C3N3S3Na3
Guaranteed content		min	15 % w/w
Physical data	Density (20°C) pH	approx. approx.	1.12 kg/L 12.5
Aspect	Colourless to slightly yellow liquid
Packaging	IBC PE-Container PE-Container		950 kg 65 kg 20 kg
Storage	Protect from frost and direct sun light. At low temperatures the product may crystallise. It may be redissolved by heating or by adding water. Shelf life in the original container: minimum one year.
Safety	Irritating to eyes. In case of contact, immediately rinse with plenty of water and consult a doctor. Wear suitable gloves and eye protection. Do not mix with oxidising agents.
CAS-No	17766-26-6
EG-No	241-749-5
UN-No	---
Transport regulations	Not classified as a hazardous material
Application	Na3T 15% is a ready to use solution for the precipitation of monovalent and bivalent heavy metals in waste water streams. It is especially suitable for mercury, copper, cadmium, silver, lead, nickel, and tin. Na3T 15% is significantly less toxic and safer to use than comparable heavy metal remediation agents. (LD50 [rat] >7000 mg/kg; NOEC [golden orfe >10L/m3; NOEC [daphnia magna] >1L/m3).