A proposal for a test method for assessment of hazard property HP 12 (“Release of an acute toxic gas”) in hazardous waste classification – Experience from 49 waste
Introduction
The Waste Framework Directive (EC, 2008) defines ‘hazardous waste’ as ‘waste which displays one or more of the (15) hazardous properties listed in Annex III’. The property H 12 ‘Waste which releases toxic or very toxic gases in contact with water, air or an acid’ was not further defined since that time. A Commission Regulation of 2014 redefined HP 12 (former H 12) as “Release of an acute toxic gas”: waste which releases acute toxic gases (Acute Tox. 1, 2 or 3) in contact with water or an acid. When a waste contains a substance assigned to one of the following supplemental hazards EUH029, EUH031 and EUH032, it shall be classified as hazardous by HP 12 according to test methods or guidelines (EC, 2014a, EC, 2014b). There is still no standardized test for measure of gases emission from waste. The UN N.5 method characterizes substances which in contact with water produce flammable gases (UN, 2003). It is mentioned in the Dangerous Goods Transport recommendations of the UN and in the CLP regulation. The volume of gas is measured manually by displacement of water in graduated flasks. It is poorly repeatable (according to INERIS experience with powders and chemicals) since the degree or type of wetting, a major parameter, is not defined (Janes, 2010, Janes, 2011). The Austrian experimental standard Önorm S 2120 also addresses only the flammable gas (contact with water and contact with a flame). The DG ENV has recently sent a mandate to Technical Committee TC 292 (Characterization of waste) of CEN to develop and validate a method for HP12.
EU Member States have revised the definition of the hazard properties (EC, 2014a, EC, 2014b). The HP 12 property is: “HP 12 Release of an acute toxic gas” waste which releases acute toxic gases (Acute Tox. 1, 2 or 3) in contact with water or an acid. When a waste contains a substance assigned to one of the following supplemental hazards EUH029, EUH031 and EUH032, it shall be classified as hazardous by HP 12 according to test methods or guidelines.’. The waste must contain a substance or substances with the hazard statements (HSC) code EUH029, EUH031 and EUH032. There is no standardized test to date for measuring the gases emitted by the waste. These hazard statement codes are the following (CLP, 2008):
“EUH029 — ‘Contact with water liberates toxic gas’ For substances and mixtures which in contact with water or damp air, evolve gases classified for acute toxicity in category 1, 2 or 3 in potentially dangerous amounts, such as aluminum phosphide, phosphorus pentasulphide.
EUH031 — ‘Contact with acids liberates toxic gas’ For substances and mixtures which react with acids to evolve gases classified for acute toxicity in category 3 in dangerous amounts, such as sodium hypochlorite, barium polysulphide.
EUH032 — ‘Contact with acids liberates very toxic gas’ For substances and mixtures which react with acids to evolve gases classified for acute toxicity in category 1 or 2 in dangerous amounts, such as salts of hydrogen cyanide, sodium azide.”
The substances with these HSC have been extracted from the CLP tables (CLP, 2008) (Table 1). The gas they can emit and their molecular formula have been added. Many substances are very reactive (specially EUH029 substances that react with water) and not likely to be found in waste because the chemical industry would destroy or neutralize them before release as waste. An exception is probably thionyl chloride present in the lithium-ion batteries (EUH029). These EUH029 substances emit in contact with water HCl and SO2, and for some H2S and PH3. Substances with hazard statement EUH031 include more common products (sulphides, polysulphides, hypochlorite, and carbamate derivatives of isocyanuric acid). They emit in contact with an acid mainly H2S and Cl2. Substances with hazard statement EUH032 mainly include cyanides (other than complex cyanides such as ferrocyanides, ferricyanides and mercuric oxycyanide), thiocyanate, and sodium fluoride. They emit in contact with an acid HCN and HF, and for some products PH3 and HN3.
In practice, the substances that can be present in waste in the ‘normal’ waste management circuits are thionyl chloride, and some hypochlorites, fluorides, cyanides, sulphides and sulfites. As mentioned, the Li-ion batteries contain thionyl chloride. Sediment and organic media can accumulate sulphides in the absence of oxygen. Some contaminants can be insolubilized as sulphides when treating effluents or chemical waste. The cyanide and fluoride are present in chemicals. Hypochlorite is present in oxidants and disinfectants. But only some salts of these anions are targeted by the CLP.
There are no routine methods of analysis in waste laboratories to identify and measure substances with HSC EUH029, EUH031 and EUH032. For example, EN 15,875 determines the sulphide content in waste from the extractive industries by difference between the total sulphur and sulphate, and assumes that the sulphide is pyrite (FeS2). It is more easy and cost-effective to start by gas detection: if a specific gas is not emitted, substances that can emit that gas are not present in the waste. The objective is to detect qualitatively if any EUH029, EUH031 or EUH032 substances are present in the waste, by their gas emission.
The waste materials potentially of concern (containing critical substances in waste for HP12) are chemical waste reacting with an acid and containing hypochlorite (disinfectant, swimming pool chemicals), sulphide (mining residues with pyrite, precipitated elements from cleaning of aqueous liquid waste by treatment with Na2S), cyanide (salts from metal surface treatment), sodium fluoride. It is expected that the waste that react with water and produce a toxic gas is pretreated in situ in the chemical industry and neutralized before joining the waste flux.
The objective of the paper is a starting point which is tested for some materials, and needs for improvements and further studies to become a full “ready” test.
Section snippets
Protocol
From Table 1, it can be seen that two gases a priori very unlikely to be met (hydrazoic acid HN3 and selenium oxide SeO2 – a solid with low vapor pressure). The gases to search (sorted by main element) are HCl, Cl2, HF, HCN, PH3, H2S and SO2.
The principle of the method proposed in this article is the following:
- 1
Measurement of the volume of gases emitted into contact with water or an acid (solid/liquid ratio of 10 L water or acid/kg raw waste, acid 2.5 M HNO3).
- 2
If gas is emitted at a rate higher
Results
For blanks with water, the temperature was monitored and an increase of 2 °C has been observed, due to heat of dilution of the acid. In the condition of the apparatus, it produces a mean pressure increase corresponding to an apparent gas emission of 0.06 L of gas/kg sample (Lg/kg). The detection limit of the test was then set to 0.1 Lg/kg. For a test sample of 1.6 g of liquid or dry mass (MS) of solid, and an internal volume of 287 ml, an emission of 1 L of gas per kg of waste corresponds to a
Conclusion
The proposed stepwise method seems quite satisfactory. Further development could be done with larger aliquots. The test is suitable for solid and liquid waste. Most of the tested samples emit gas in contact with concentrated hydrochloric acid, but it is mainly CO2. Human toxic gases are potentially emitted by three waste: metallic dust from the aluminum industry (CO), two air pollution control residue from industrial waste (H2S) and a halogenated solvent (gas with a response to alcane
Acknowledgements
The professional unions of waste industries SYVED and SYPRED (F) are acknowledged for supplying samples of most of the waste used in this study. This research was financially supported by Ministère de l’Ecologie et du Développement Durable, France.
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