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Nanoparticles Survive Waste Incineration & Contaminate Fly Ash

Nanoparticles Survive Waste Incineration & Contaminate Fly Ash

07 December 2012

A new study conducted on behalf of the European Commission’s Environment Directorate-General (DG) has shown that nanoparticles can pass through the waste incineration process into fly ash and slag and end up in landfill.

According to the study, the first to follow the fate of engineered nanoparticles through the entire waste incineration chain, the use of nanomaterials in consumer goods is growing, as is their presence in waste.

Engineered nanoparticles are often designed to be insoluble and stable when incorporated into consumer goods, so as not to be released during use, but according to the report this can cause problems if they enter the environment as they may reside for a long time.

The study focused on the nano form of cerium oxide (nano-CeO2), which has a wide range of uses, for example, in ceramics and as a glass polisher.

The researchers added nano-CeO2 particles to waste destined for a large-scale incinerator. The nanoparticles were introduced either directly onto the waste before incineration or into the gas stream exiting the furnace.

Samples were then taken from the flue gas and the residues of the combustion process, such as the fly ash, slag and slag water, and were then analysed for cerium content.

The results showed that the filter systems in the incinerator were highly effective, removing nearly 100% of the nano-CeO2. According to the researchers this suggests that no significant nano-CeO2 emissions can be expected from thermal waste to energy plants provided they have up-to-date flue gas cleaning systems.

The study said that the filters are effective because the nano-CeO2 binds loosely to the solid residues from the combustion process, which can then be efficiently removed using the filter technology.

However, the report also found that the nano-CeO2 is still present in the residues of fly ash and slag and, moreover, its chemical and physical properties have remained unchanged.

This suggests that the problem of disposal is shifted to the handling of slag and fly ash residues in landfills and final deposits.

The study cautioned that exposure to nanoparticles may occur during transportation or immediate storage, or if the slag or fly ash is treated for material recovery, for example, to recover copper, aluminium or zinc.

The research strongly recommends the use of the precautionary principle in developing measures to control nanoparticle waste and further exploring development of degradable nanoparticles.

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