Thursday, July 4, 2019

home experiment - Can I somehow 'reuse' the chemicals in glow sticks?


I particulary enjoy performing chemical experiments without buying any chemicals for them.


I was always sad about the fact that one glowstick lights out, you just throw it into trash can (I like all means of recycling). So I was wondering if I could (pick one or more):



  1. Recycle the chemicals in it to make it glow again

  2. Use the chemicals for other interesting (and maybe even useful) experiment




Answer



Here is a generalized version of what's going on chemically. The key steps are dioxetane formation (the highly strained 4-membered ring) and its subsequent decomposition and energy transfer to a fluorescent dye, which then decays back to its ground state by emitting light. By using different fluorescers, you can change the wavelength (color) of the light emitted.


enter image description here


Each company that manufactures glowsticks has their own patent(s) and proprietary process, hence the variation from product to product.



So I was wondering if I could (pick one or more): 1.Recycle the chemicals in it to make it glow again 2.Use the chemicals for other interesting (and maybe even useful) experiment



1) Since the starting oxalate ester and concentrated hydrogen peroxide are consumed in the reaction, to make it glow again you would need to put in a new batch of both the oxalate ester and concentrated hydrogen peroxide. You probably wouldn't want to open the glowstick because:



  • there might be some concentrated hydrogen peroxide remaining (if I were the manufacturer, I would want this cheap reagent present in a slight excess to make sure all of the ester is consumed)


  • many of the commonly used fluorescers are irritants, both externally and internally

  • phthalate esters are commonly used as solvents and they pose health risks


2) Even after all of the starting materials are used up, the fluorescer still remains in solution. Exposing the glowstick to a black light will still cause it to fluoresce.


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