Photo Oxidation to Control Trash Room Odors

//
Home » Trash Talk » WasteXperts' Products » Photo Oxidation to Control Trash Room Odors

The Clean AirActUVator reduces or eliminates trash room odors by using Ultraviolet light (UV-C and UV-V) to cause chemical oxidation of the odor-causing molecules. This is the same process that occurs naturally outside in the atmosphere by interaction with sunlight.

Odor Molecules Broken Down by UV Light

An example would be hydrogen sulfide molecules (H2S), which you might recognize as “rotten egg smell.” When hydrogen sulfide is oxidized, it converts to a completely odorless molecule of water (H2O) and a molecule of sulfur dioxide (SO2) that has an odor threshold that is 50,000 times less odorous than the initial hydrogen sulfide molecule.

Normally, an oxidation reaction requires a high temperature to get started. For instance, the oxidation of fuels like wood or natural gas occurs through “combustion.” There is however another way to initiate chemical oxidation reactions by using high-energy photons from UV light. This process of oxidation at ambient temperature is called “photolysis” or “photo-oxidation”.

The amount of energy carried by a photon depends on the wavelength of the light. UV photons are more energetic than the red photons at the opposite end of the light spectrum. The more the photons have energy, the more they are like a big caliber bullet capable of breaking the bonds between atoms within a molecule. Once those bonds are broken, the atoms can combine with oxygen atoms to become less odiferous molecules like water.

By using ultraviolet light sources with wavelength of 254 nm for UV-C and 185 nm for UV-V respectively, it is possible to emit photons with energies large enough to break and then oxidize most of the molecules that commonly cause trash room odors (such as those listed in the table below).

Odor Class and
Molecule Types
Characteristic Odor
Sulfured:
Hydrogen Sulfide
Methylmercaptan
Dimethylsulphur
Dyethylsulphur
Dimeththlysulphur

Rotten Egg
Cabbage and Garlic
Decaying Cabbages
Vegetables
Decomposition
Ethereal
Putrid
Nitrogenous:
Ammonia
Methylamine
Ethylamine
Dimethylamine
Indole
Scatole
Cadaverine
Very Spicy, Irritating
Rotten Fish
Spicy, Ammoniacal
Fecal, Nauseous
Decaying Meat
Organic Acids:
Acetic
Butyric
Valeric
Vinegar
Rancid Butter
Sweat
Table 1. Common Bad Odor Molecules Generated by Organic Decomposition of Household Waste

By way of example, let’s have a closer look at the steps of photo-oxidation process of hydrogen sulfide (H2S). The first step is to break the chemical bond between the sulfur atom S and the hydrogen atom H. The energy of this bond is easily broken by UV-C photons, momentarily freeing the sulfur and hydrogen atoms. The second step is to bring some oxygen atoms to react with the sulfur and hydrogen atoms. The ambient air contains many oxygen atoms (close to 21% of the air volume, the remainder being essentially nitrogen), but they are bound together in molecular pairs (O2). The UV-C photons do not carry enough energy to break this bond and release oxygen atoms, but the UV-V photons exceeds the binding energy of oxygen molecules, easily breaking them up.

Once these two steps are done, the oxidation reaction will occur at ambient temperature via a hydroxyl (OH *) radical which serves as a transmission media for free oxygen atoms. The end result is the conversion by oxidation of odorous molecules into other molecules that have little or no odor at all.

References:
Garbage Room Odors Remediation By: Normand Brais P.Eng., M.A.Sc., Ph.D

Learn more about how to control trash room odors with the Clean Air ActUVator.

Leave a Comment