Color Removal by Exposing Product to Light

[TechSupport1]

Our facility has a product that has a high color content. The goal is to remove the color from the product by exposing it to light. Some research has been done to determine what wavelength of color is most effective; sunlight will work. Does anyone have experience in process design in a chemical plant where a product is exposed to light? Please comment.

 

[unclesyd]

You are dealing with light fastness or a lack thereof of a component in or on you product. There are labs that will determine the wavelength of light needed to affect the color of the component.
If you think sunlight will do the trick you might find a lab with a Suntester like Heraeus Xenotest that can accelerate this testing.

Just remember that Sunlight, UV rays, are very detrimental to a lot of materials.

 

[TechSupport1]

I have some ideas to expose the sunlight to the product: 1. install glass piping and circulate the storage tank using its centrifugal pump. 2. install translucent (or transparent) piping material and pump through the line as the tank is circulated. 3. install a lamp inside the storage tank. 4. use a lens to intensify sunlight and project the light into the product storage tank.

Concerns I have with these ideas are as follows: 1. glass is obviously very brittle and if cracked and/or broken, hydrocarbon could be released to the environment or worse could fuel a fire. 2. translucent piping could melt in the event of a fire and add fuel to a fire. 3. a lamp inside a storage tank would have to comply with Class I Div I electrical classification. 4. how practical are these ideas? Have these ideas or some variation of them or something completely different been immplemented in other chemical plants to remove the color from the product?

 

[IRstuff]

You seem to talking about sun bleaching, which, of course, for textiles, is a time-venerated process. Your concern about flammability seems to imply that your "product" is also flammable, in which case, there is a likelihood that it can dissolve non-glass materials such as acrylics.

I would dispute you assertions about the fragility of glass. There are a multitude of glasses such as tempered glass or Pyrex that are quite durable. And unless you expect that someone is going to be beating on your glass with a hammer or other shock load, there shouldn't be any issue.

Since the bleaching process is going to be exposure time dependent, you need a LARGE area of exposure, e.g., something with a large window with some length in the direction of flow.

Piping is very inefficient for this, because the curvature of the piping causes reflections and reduces the amount of light that actually reaches the fluid.

TTFN

 

[unclesyd]

I think you need to give this fellow a call. Looks like he has put light in pipe. If correct, his UV intensities are huge or better put many suns.

http://www.oxilume.com/index.html

 

[TechSupport1]

Thank you to unclesyd for your responses. I have contacted oxilume.

Thank you to IRStuff for your response. Could you provide a company, consultant, or literature that I could contact? I would be very interested in talking to someone who could help us out. Do you have any other information or suggestions for us to consider?

 

[moltenmetal]

Better conclude WHAT wavelengths in sunlight are doing the photochemistry you want done. Then you need to know what dose of that wavelength or range of wavelengths (i.e. how many photons of useful light must be absorbed) per unit volume is required to obtain the required bleaching. A simple experiment monitoring the optical density versus time during irradiation at a particular wavelength will give you what you need.

Generally, design can be scaled up to give the same dose absorbed per unit volume, since most photochemistry of commercial interest is pretty much independent of intensity (i.e. one watt of light absorbed in a given volume for one second gives the same result as ten watts absorbed for 1/10th of a second).

Do be aware that while the desired photochemistry may be occurring (i.e. the colour may be going away), undesired photochemistry might also be occurring, contaminating your product with photolysis byproducts or degrading the product itself.

If you find that sunlight works, you may not get the same result with 254 nm low pressure mercury germicidal lamps because the wavelength distribution (hence the energy of the absorbed photons) is very different between the two sources.

If it's the UV or near UV in sunlight doing the bleaching, then putting the material through a glass pipe or under a glass window exposed to sunlight won't do you a bit of good. Most commercial glasses are strongly absorptive in the short UV and relatively strongly absorptive in the near- UV. You may need quartz to get the transparency to UV that you require. And the sun isn't a reliable source of UV, nor even an economical one except if your product can just be left laying around on a concrete slab for an extended period.

There are several companies involved in commercial photochemical process equipment, including equipment designed to work with materials in flammable solvents etc. You can try Hanovia or Heraeus as a couple to start with. Commercial photochemical equipment is used for all sorts of processes, from the production of caprolactam to the synthesis of vitamin D to the purification of process- and wastewater.

 

[JStephen]

They use UV light for sterilizing potable water; information on that topic might be of interest to you, although the goal is a bit different.

 

[m777182]

I have forgoten the exact mechanism of colour origin in a compound but I think it has to do with a resonance of a chemical bond; however there is perhaps a way to treat your compound chemicaly to destroy those bonds. UV or other wavelenght light will do the same.
There is another way- to add some coloured compound to mask your primary colour, as we did times ago with coloured diesel oil used for domestic heating, which was transformed this way to a diesel fuel.
m777182