Potassium O-isobutyl dithiocarbonate

Endpoint summary

Additional information

 Stability

 

Phototransformation in air

 

If released to air, a vapor pressure of 1.26E-009 mm Hg at 25 deg C (1.26E-009 mm Hg is equivalent to 1.68E-007 Pa ) indicates that Potassium isobutyl xanthate will exist solely as a vapor in the atmosphere. Vapor-phase Potassium isobutyl xanthate will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 0.757 days, calculated from its rate constant of 14.1324 E-12  cm3/molecule-sec at 25 deg.

Xanthates do not contain chromophores that absorb at wavelengths >290 nm and therefore Potassium isobutyl xanthate is not expected to be susceptible to direct photolysis by sunlight.

Using the AOPWIN QSAR model, the photochemical degradation rate of Potassium isobutyl xanthate in the atmosphere is 14.1324 E-12 cm3/molecule-sec, with a resultant predicted half live of 9.082 Hrs (0.757 Days (12-hr day; 1.5E6 OH/cm3).

OVERALL OH Rate Constant = 14.1324 E-12 cm3/molecule-sec

 HALF-LIFE =    0.757 Days (12-hr day; 1.5E6 OH/cm3)

 HALF-LIFE =    9.082 Hrs

Phototransformation in water

It is not applicable for a compound wich dissociates.

When water is added to Potassium isobutyl xanthate it reacts with water to form the others substances: alcohol, potassium carbonate, trithiocarbonate and carbon disulphide because of its high water solubility.

 

Phototransformation in soil

If released to soil, Potassium isobutyl xanthate is expected to have very high mobility based upon an estimated Koc of 11.18. Volatilization from moist soil surfaces is not expected to be an important fate process.

Therefore testing for Phototransformation in soils does not need to be performed.

 

Hydrolysis

 

Hydrolysis is a chemical reaction during which molecules of water (H2O) are split into hydrogen cations (H+, conventionally referred to as protons) and hydroxide anions (OH−) in the process of a chemical mechanism).

 

When water is added to potassium isobutyl xanthate it reacts with water to form the others substances: alcohol, potassium carbonate, trithiocarbonate and carbon disulphide.

 

On this basis, Potassium isobutyl xanthate does not have a potential for Hydrolysis and potassium ion will not hydrolise.

 

On the other basis hydrolysis may proceed with the others active substances:

 Further hydrolysis of potassium trithiocarbonate to potassiumcarbonate and hydrogen sulphide and carbon disulphide to carbon dioxide and hydrogen sulphide may occur. The reaction is catalysed by the alcohol formed from the xanthic acid and is self accelerating.

 

On this basis hydrolysis proceed with the others active substances: potassium trithiocarbonate, carbon disulphide, hydrogen sulphide.

 

Xanthates decompose in aqueous solution by dissociation, oxidation and hydrolysis. Hydrolytic decomposition is the main reaction in alkaline solutions while the other two reactions occur in acidic solutions.

 

Aqueous solution

There are three decomposition pathways of xanthates in aqueous solution:

A. Xanthates dissociate forming alkali metal cations and xanthate anions. The solution undergoes further hydrolysis to xanthic acid which decomposes into carbon disulphide and alcohol.

ROCS2Na + H2O → ROCS2H + NaOH

 

ROCS2H → CS2 + ROH

 

B. Xanthate is oxidised to dixanthogen. The extent of this reaction is very small and dependent on the pH. Equilibrium is reached after about 5–10% of the xanthate is oxidised, and the reaction increases with a fall in the pH.

 

2ROCS–2 + H2O + _O2 →(ROCS2)2 + 2OH–

 

C. In neutral and alkaline media, xanthates decompose by hydrolytic decomposition.

6ROCS–2 + 3H2O →6ROH + CO3 2 – + 3CS2 + 2CS3 2 –

Further hydrolysis of potassium trithiocarbonate to potassium carbonate and hydrogen sulphide and carbon disulphide to carbon dioxide and hydrogen sulphide may occur. The reaction is catalysed by the alcohol formed from the xanthic acid and is self accelerating.

 

Reaction C is the main reaction in alkaline solution while A and B occur in acidic solutions. During use in mining processes, reaction C is the principal decomposition pathway and carbon disulphide the principal decomposition product.

Part of the carbon disulphide formed may decompose further to carbonate and thiocarbonate salts, some of it may evaporate and some may build up in the xanthate solution. Once the solubility of carbon disulphide is exceeded it forms a separate layer below the potassium isobutyl xanthate solution.

Reactions A and B are minor and require acidic conditions. Reaction C proceeds in neutral or alkaline pH and is self-accelerating, as it is catalysed by the alcohol formed as a product. Its rate increases with concentration of the reagents and with temperature, from 1.1%/day at 20 °C to 4.6%/day at 40 °C for a 10% solution at pH=10. A decrease in pH from 10 to 6.5 increases the decomposition rate from 1.1%/day to 16%/day. Decomposition is also accelerated by the presence of metals, such as copper, iron, lead or zinc, which act as a catalyst.