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EC number: 235-837-2 | CAS number: 13001-46-2
Endpoint summary
Administrative data
Description of key information
Additional information
Environmental fate and pathways
Environmental Fate/Exposure Summary:
Environmental exposure
Potassium isobutyl xanthate is used as a collector during the processing of sulphide ores by flotation, a process that involves addition of the reagent to aqueous slurries ofcrushed and finely ground ore contained in flotation tanks. Air is blown through theslurry. In general, a series of such tanks is used. During the use of Potassium isobutyl xanthate in the flotation process the mineral particles become separated as a frothfrom the tailings, which settle at the bottom of the flotation tank.
The froth (float) is collected and dried, either in air under ambient conditions or atelevatedtemperatures in an oven,while the tailings are conveyed as a slurry to atailings dam where they settle, dry and consolidate. Spills and washings wouldalso be directed to tailings dams. Tailings typically have a solids content of about 30%. In some operations, tailings may be intercepted in settling tanks so thatwastewater containing low concentrations of xanthates can be recovered for reuse inflotation. Xanthates in the tailings are not monitored, but most would be expected to beretained in the froth. Xanthate residues in the ore concentrate are expected to decomposeduring drying or smelting.
Environmental fate
Hydrolysis will be a significant factor in determining the environmental fate of Potassiumisobuty lxanthate. In neutral or mildly alkaline solutions, Potassium isobutyl xanthate decomposes to the alcohol, carbon disulphide, potassium carbonate and potassium trithiocarbonate, the two salts arising from neutralisation of carbon disulphide with the potassium hydroxide liberated. In more strongly alkaline media,hydrogen sulphide is liberated. However, strongly alkaline conditions are unlikely to be encountered under the conditions of use in the mining industry. The half-life at pH 7 at 25°C is reportedly about 260 hours, increasing to over 500 hours in the pH range 8 to 11.
Potassium isobutyl xanthate is hydrolytically unstable when exposed to acidic conditions, reverting rapidly to isobutyl, carbon disulphide and potassium hydroxide, and therefore will not persist in the acidic environment of tailings dams. If discharged to waterways, the chemical would be likely to persist for at least some days, hydrolysing only slowly in this more neutral environment. However, it is not expected to bioaccumulate in view of its ionic character.Potassium isobutyl xanthate is not expected to contaminate the environment where oretailings are confined to well constructed tailings dams. Most will be retained on sulphide minerals and destroyed when they are dried after flotation. Minor residues that remain associated with tailings will be destroyed by hydrolysis intailings dams.
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 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.
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.
Biodegradation
Biodegradation in water: screening tests
When water is added to Potassium isobutyl xanthate it reacts with water to form the others substances: alcohol, potassium carbonate, trithiocarbonate and carbon disulphide.
Carbon disulphide (CAS number 75–15–0) it is the major decomposition product, which is liquid and have to be considered.
The biodegradation of CS2 was >80 % after 28 days of exposure, therefore CS2 is readily biodegradable. Potassium isobutyl xanthate readily decomposes to carbon disulphide, especially in the presence of moisture/water.
Therefore, the Biodegradation in water of carbon disulphide (CS2) need to be considered in the assessment of potassium isobutyl xanthate.
The biodegradation of Isobutyl Alcohol was >74 % after 28 days of exposure, therefore Isobutyl Alcohol is readily biodegradable. Potassium isobutyl xanthate readily decomposes to Isobutyl Alcohol, especially in the presence of moisture/water. Isobutyl Alcohol is both reagents used in the manufacture, as well as decomposition products.
Therefore, the Biodegradation in water of Isobutyl Alcohol need to be considered in the assessment of potassium isobutyl xanthate.
These results suggest that potassium isobutyl xanthate will be readily biodegradable and it is not expected to persist in the environment.
Biodegradation in water and sediment: simulation tests
Potassium isobutyl xanthate readily decomposes to carbon disulphide, especially in the presence of moisture/water. Therefore, the Biodegradation in water of carbon disulphide (CS2) need to be considered in the assessment of potassium isobutyl xanthate.
Due to their structural similarity, it is expected that all xanthates would have similar Biodegradation effects either due to the xanthate or carbon disulphide.
On this basis, testing for Biodegradation in water for Potassium isobutyl xanthate is not applicable
Carbon disulphide (CAS number 75–15–0) it is the major decomposition product, which is liquid and have to be considered.
According to “ANNEX IX- STANDARD INFORMATION REQUIREMENTS FOR SUBSTANCES MANUFACTURED OR IMPORTED IN QUANTITIES OF 100 TONNES OR MORE”, a simulation testing on ultimate degradation in surface water, the study does not need to be performed if the substance is ready biodegradable. As Potassium isobutyl xanthate is ready biodegradable a ready biodegradability study does not need to be conducted.
Therefore testing for Biodegradation in water does not need to be performed.
Biodegradation 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 biodegradation in soil does not need to be performed.
Bioaccumulation
This substance has a limited potential to bioaccumulate (based on log Kow used :, Log Kow estimated : 1.78 , and predicted bioconcentration factors, log BCF = 0.84 (EPIWIN/BCF Program).
The estimated BCF of 6.899 L/kg wet-wt was measured by calculation from EPI SuiteTM v4.1 Program.
These values would suggest very low bioaccumulation potential.
This is Exposure Assessment Tools and Models made from EPA (Environmental Protection Agency).
BCFBAF Program (v3.01) Results:
==============================
SMILES : S=C(S)OCC(C)C
CHEM : Carbonodithioic acid, o-(2-methylpropyl) ester, potassium salt
MOL FOR: C5 H10 O1 S2
MOL WT : 150.25
--------------------------------- BCFBAF v3.01 --------------------------------
Summary Results:
Log BCF (regression-based estimate): 0.84 (BCF = 6.9 L/kg wet-wt)
Biotransformation Half-Life (days) : 0.0884 (normalized to 10 g fish)
Log BAF (Arnot-Gobas upper trophic): 0.72 (BAF = 5.29 L/kg wet-wt)
Log Kow used by BCF estimates: 1.78
Equation Used to Make BCF estimate:
Log BCF = 0.6598 log Kow - 0.333 + Correction
Correction(s): Value
No Applicable Correction Factors
Estimated Log BCF = 0.839 (BCF = 6.899 L/kg wet-wt)
Bioaccumulation: terrestrial
This substance has a limited potential to bioaccumulate (based on log Kow used :, Log Kow estimated : 1.78 , and predicted bioconcentration factors, log BCF = 0.84 (EPIWIN/BCF Program).
The estimated BCF of 6.899 L/kg wet-wt was measured by calculation from EPI SuiteTM v4.1 Program.
These values would suggest very low bioaccumulation potential.
This is Exposure Assessment Tools and Models made from EPA (Environmental Protection Agency).
BCFBAF Program (v3.01) Results:
==============================
SMILES : S=C(S)OCC(C)C
CHEM : Carbonodithioic acid, o-(2-methylpropyl) ester, potassium salt
MOL FOR: C5 H10 O1 S2
MOL WT : 150.25
--------------------------------- BCFBAF v3.01 --------------------------------
Summary Results:
Log BCF (regression-based estimate): 0.84 (BCF = 6.9 L/kg wet-wt)
Biotransformation Half-Life (days) : 0.0884 (normalized to 10 g fish)
Log BAF (Arnot-Gobas upper trophic): 0.72 (BAF = 5.29 L/kg wet-wt)
Log Kow used by BCF estimates: 1.78
Equation Used to Make BCF estimate:
Log BCF = 0.6598 log Kow - 0.333 + Correction
Correction(s): Value
No Applicable Correction Factors
Estimated Log BCF = 0.839 (BCF = 6.899 L/kg wet-wt)
===========================================================
Whole Body Primary Biotransformation Rate Estimate for Fish:
===========================================================
------+-----+--------------------------------------------+---------+---------
TYPE | NUM | LOG BIOTRANSFORMATION FRAGMENT DESCRIPTION | COEFF | VALUE
------+-----+--------------------------------------------+---------+---------
Frag | 2 | Methyl [-CH3] | 0.2451 | 0.4902
Frag | 1 | -CH2- [linear] | 0.0242 | 0.0242
Frag | 1 | -CH- [linear] | -0.1912 | -0.1912
L Kow| * | Log Kow = 1.78 (KowWin estimate) 0.3073 | 0.5458
MolWt| * | Molecular Weight Parameter | | -0.3853
Const| * | Equation Constant | | -1.5058
============+============================================+=========+=========
RESULT | LOG Bio Half-Life (days) | | -1.0534
RESULT | Bio Half-Life (days) | | 0.08844
NOTE | Bio Half-Life Normalized to 10 g fish at 15 deg C |
============+============================================+=========+=========
Biotransformation Rate Constant:
kM (Rate Constant): 7.838 /day (10 gram fish)
kM (Rate Constant): 4.407 /day (100 gram fish)
kM (Rate Constant): 2.479 /day (1 kg fish)
kM (Rate Constant): 1.394 /day (10 kg fish)
Arnot-Gobas BCF & BAF Methods (including biotransformation rate estimates):
Estimated Log BCF (upper trophic) = 0.724 (BCF = 5.293 L/kg wet-wt)
Estimated Log BAF (upper trophic) = 0.724 (BAF = 5.293 L/kg wet-wt)
Estimated Log BCF (mid trophic) = 0.634 (BCF = 4.31 L/kg wet-wt)
Estimated Log BAF (mid trophic) = 0.634 (BAF = 4.31 L/kg wet-wt)
Estimated Log BCF (lower trophic) = 0.602 (BCF = 4 L/kg wet-wt)
Estimated Log BAF (lower trophic) = 0.602 (BAF = 4.001 L/kg wet-wt)
Arnot-Gobas BCF & BAF Methods (assuming a biotransformation rate of zero):
Estimated Log BCF (upper trophic) = 0.862 (BCF = 7.278 L/kg wet-wt)
Estimated Log BAF (upper trophic) = 0.870 (BAF = 7.407 L/kg wet-wt)
Transport and distribution
Adsorption / desorption
According to “ANNEX IX- STANDARD INFORMATION REQUIREMENTS FOR SUBSTANCES MANUFACTURED OR IMPORTED IN QUANTITIES OF 100 TONNES OR MORE , an adsorption study need not be conducted if:
— based on the physicochemical properties the substance can be expected to have a low potential for adsorption (e.g. the substance has a low octanol water partition coefficient), or
— the substance and its degradation products decompose rapidly.
The log of the adsorption coefficient (KOC) of Potassium isobutyl xanthate was estimated to be log KOC = 1.048 which is equal to a KOC value of 11.18 using the KOCWIN v2.00 QSAR method. This value indicates that Potassium isobutyl xanthate will be adsorbed by organic carbon in soil. Potassium isobutyl xanthate can be classified to be of very high mobility in soil according these results and does not have a high potential for adsorption to soil
Potassium isobutyl xanthate and xanthates in general adsorbs strongly to sulphide minerals but has less affinity for surfaces in general. The KOC value of 11.18 also suggest this conclusion.
The estimated Soil Adsorption Coefficient was 11.18 L/kg measured by calculation from EPI SuiteTM v4.1 Program. This is Exposure Assessment Tools and Models made from EPA (Environmental Protection Agency
SMILES : S=C(S)OCC(C)C
CHEM : Carbonodithioic acid, o-(2-methylpropyl) ester, potassium salt
MOL FOR: C5 H10 O1 S2
MOL WT : 150.25
--------------------------- KOCWIN v2.00 Results ---------------------------
Koc Estimate from MCI:
---------------------
First Order Molecular Connectivity Index ........... : 3.626
Non-Corrected Log Koc (0.5213 MCI + 0.60) .......... : 2.4900
Fragment Correction(s):
1 Thiocarbonyl (C=S) .................. : -0.5701
1 Ether, aliphatic (-C-O-C-) .......... : -0.8716
Corrected Log Koc .................................. : 1.0483
Estimated Koc: 11.18 L/kg <===========
Koc Estimate from Log Kow:
-------------------------
Log Kow (Kowwin estimate) ......................... : 1.78
Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 1.9097
Fragment Correction(s):
1 Thiocarbonyl (C=S) .................. : 0.3004
1 Ether, aliphatic (-C-O-C-) .......... : -0.0906
Corrected Log Koc .................................. : 2.1195
Estimated Koc: 131.7 L/kg <===========
Henry's Law constant
The estimated Henrys Law Constant (25 deg C) measured by calculation from EPI SuiteTM v4.1, HENRYWIN v3.20 Program was 4.59E-005 atm-m3/mole (4.65E+000 Pa-m3/mole) , which is almost zero.
This is Exposure Assessment Tools and Models made from EPA (Environmental Protection Agency)
Distribution modelling.
Potassium isobutyl xanthate has no affinity to be in air and sediment. The direct emissions to soil and surface water are significant, therefore Potassium isobutyl xanthate will be almost exclusively be found in soil and surface water.
Mackay fugacity modelling (level 3) indicates that, taking into account degradation and using inflow parameters which are consistent with the known production tonnage of this substance in, fugacity coefficient indicates that environmental concentrations in water are predicted to be 7.04e-021 (atm), in air (atm) 2.43e-019 and soil 3.22e-019 (atm) and sediment to be 6.39e-021 (atm).
These are negligible low levels. This can be considered a worse case prediction as it assumes all product is emitted with no emission control systems used.
Other distribution data
These results suggest for Potassium isobutyl xanthate that direct and indirect exposure from distribution in media is unlikely.
Based on low vapor pressure and low estimated log Pow, expected to partition to water and soil. Not expected to partition to air, sediments or biota.
Therefore testing for distribution in media does not need to be performed.
The estimated STP Fugacity Model and Volatilization From Water were measured by calculation from EPI SuiteTM v4.1 Program. This is Exposure Assessment Tools and Models made from EPA (Environmental Protection Agency) .
Volatilization From Water
=========================
Chemical Name: Carbonodithioic acid, o-(2-methylpropyl) ester, potassium salt ( potassium O-isobutyl dithiocarbonate)
Molecular Weight : 188.34 g/mole
Water Solubility : 6.827E+005 ppm
Vapor Pressure : 1.26E-009 mm Hg
Henry's Law Constant: 4.57E-016 atm-m3/mole (calculated from VP/WS)
RIVER LAKE
--------- ---------
Water Depth (meters): 1 1
Wind Velocity (m/sec): 5 0.5
Current Velocity (m/sec): 1 0.05
HALF-LIFE (hours) : 1.757E+012 1.916E+013
HALF-LIFE (days ) : 7.32E+010 7.985E+011
HALF-LIFE (years) : 2.004E+008 2.186E+009
STP Fugacity Model: Predicted Fate in a Wastewater Treatment Facility
======================================================================
(using 10000 hr Bio P,A,S)
PROPERTIES OF: potassium O-isobutyl dithiocarbonate
-------------
Molecular weight (g/mol) 188.34
Aqueous solubility (mg/l) 682700
Vapour pressure (Pa) 1.67986E-007
(atm) 1.65789E-012
(mm Hg) 1.26E-009
Henry 's law constant (Atm-m3/mol) 4.57371E-016
Air-water partition coefficient 1.87051E-014
Octanol-water partition coefficient (Kow) 0.0467735
Log Kow -1.33
Biomass to water partition coefficient 0.809355
Temperature [deg C] 25
Biodeg rate constants (h^-1),half life in biomass (h) and in 2000 mg/L MLSS (h):
-Primary tank 0.04 16.16 10000.00
-Aeration tank 0.04 16.16 10000.00
-Settling tank 0.04 16.16 10000.00
STP Overall Chemical Mass Balance:
---------------------------------
g/h mol/h percent
Influent 1.00E+001 5.3E-002 100.00
Primary sludge 2.50E-002 1.3E-004 0.25
Waste sludge 1.51E-001 8.0E-004 1.51
Primary volatilization 2.49E-013 1.3E-015 0.00
Settling volatilization 6.79E-013 3.6E-015 0.00
Aeration off gas 1.67E-012 8.9E-015 0.00
Primary biodegradation 1.76E-003 9.3E-006 0.02
Settling biodegradation 5.27E-004 2.8E-006 0.01
Aeration biodegradation 6.93E-003 3.7E-005 0.07
Final water effluent 9.82E+000 5.2E-002 98.15
Total removal 1.85E-001 9.8E-004 1.85
Total biodegradation 9.22E-003 4.9E-005 0.09
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