Fumigation of shipping containers with methyl iodide

[Grant Knight]

Dear Forum Members.

 

Worldwide, the most commonly used fumigant to rid shipping containers of pests is methyl bromide. It is highly efficient at doing this but it is being phased out, worldwide, because it is an ozone layer depleter. Methyl iodide (MeI) is being considered as a substitute fumigation gas. It is equally efficient but has a much shorter atmospheric lifetime (and negligible ozone depletion potential) but is much less volatile. It is proposed to use it in combination with heat treatment where hot air (~45 degrees C) containing about 25g of methyl iodide/cubic m is circulated through the container in a closed system.

It is becoming less acceptable to discharge such a toxic material as MeI to the air, untreated, and I am looking for some way of adding a reagent to the circulating MeI to immobilise it/convert it to a non-toxic material inside the container, or discharge the MeI/hot air through an external reactor to do similar. A candidate for this is dimethyl sulphoxide which reacts with MeI to form a non-volatile sulfoxonium salt (CH3)3 SOI. Does anybody know if this would be a practical reaction to perform, in the gas phase, within the container, if DMSO was titrated into the circulating hot gas, as an aerosol, at the end of the decontamination time? Is the reaction time under these conditions sufficiently fast?

Is there another (cheap, readily available, low toxicity, volatile as an aerosol @ ~40 - 45 degrees C) compound that would do a better job under these conditions than DMSO.

 

I would greatly appreciate your thoughts and ideas,

 

Grant Knight

 

email grant.knight@maf.govt.nz

Edited January 28, 2009 by Grant Knight
addition of email

[hermanntrude]

I think DMSO would be a really bad idea. it smells AWFUL. I think it's also fairly hazardous.

[DrDNA]

Do you know what the boiling point of DMSO is?

Also, do you know what happens when you mix a toxic substance or drug with DMSO and apply it too skin?

[Grant Knight]

I think DMSO would be a really bad idea. it smells AWFUL. I think it's also fairly hazardous.

 

DMSO is practically odourless, virtually non-toxic in small quantities, it is used in skin patches to aid in transferring medication across the skin barrier. It is also used to cryo-preserve tissue for transplant.

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Do you know what the boiling point of DMSO is?

Also, do you know what happens when you mix a toxic substance or drug with DMSO and apply it too skin?

Hi DrDNA,

The melting point of DMSO is about 18 degrees C, boiling point about 189 degrees C. It can ge aerosolised and vaporised at about 40 -50 degrees. It is not a good idea to get both a toxic substance and DMSO on your skin because the DMSO greatly enhances monement across the skin. With the style of fumigation I decribed, above, there is no handlling of the chemicals. They are all injected mechanically into the closed shipping container.

[UC]

I think DMSO would be a really bad idea. it smells AWFUL. I think it's also fairly hazardous.

 

No, I believe you'e thinking of dimethylsulfide.

 

DMSO by itself is largely harmless. It has a mild, but distinctive smell. The point of using MeBr is that it's a gas and will leave the container after treatment. The route with DMSO leaves a solid, and to effect complete reaction (if it even happens easily at room temp) you'd need an excess. Because it's b.p. is so high, you'll get the aerosol soaked into surfaces and it has no plans of evaporating very fast, possibly ruining the material in the shipping container and giving everything an odd smell.

[CaptainPanic]

You're planning on mixing two different gases, and then get a salt to form in mid-air... Hmm... Wouldn't that make everything a bit dirty? And in addition, you'll have to buy quite a lot of gas. Finally, DMSO boils at 189 deg C, which will make it a bit hard to vaporize it. You can't heat containers to >100 degrees. Some products inside might not like that

 

I think a more conventional way to clean air would be to vent it into a scrubber, where you scrub the air from this methyliodine.

This means you'll have to blow the MeI+air towards the scrubber. You'll therefore have to blow clean air into the container... this will dilute the MeI even more... but still better than reacting it all away to some salt.

 

You might even be able to recover the MeI from the scrubbing liquid (in case you use a wet-scrubber). I don't know what would be a good liquid or a good design for this. I'd have to think a bit longer, and possible test the solubility of MeI in a couple of liquids.

 

Before trying this out (I'm not sure if you're a Do-It-Yourself kinda person), please consider mass transfer - a badly designed scrubber does not work... but a good one can have many benefits

[hermanntrude]

i'm sure ive used DMSO as a solvent and had smell issues. perhaps the two weren't related though...

[John Cuthber]

DMSO doesn't smell much but one of its uses is as an oxidant. The by product (the sulphide) really stinks.

 

I think a scrubber with an amine might be a better idea- such scrubbers are used for cleaning up gas streams anyway so the technology isn't new. How fast MeI reacts with, for example, ethanolamine, is another matter.

[DrDNA]

Gamma Irradiation works well for produce.