Unknown Plastic Waste Workflow

Basics

• In recycling it is best done with pre-sorting and/or labels/indicators on the plastic itself
• In most collection systems this is do-able
• The main area where this becomes an issue are small debris and/or degraded plastic
• This is common in picking up waste such as Beach Plastic
• Thus in order to aid in recycling efforts a sorting and processing workflow is needed
• This page also assumes the user does not have a Plastic Type Sensor available
• So far this page's process is mainly done via sink/float tanks, but we should also look into:
  • Air Classification
  • Froth Flotuation
  • Misc advanced cyclones and hydrocyclones (may only be effective large scale, some papers were adapting mining processing techniques)

Process Proposal 1

Basics

• Uses float/sink seperation using these media:
  • Water
  • Brine / Concentrated Salt Water
  • Oil (most likely canola/rapeseed or mixed plant oil, but any oil should work)
  • Potentially any alchohol, or sugar solution?

Pre-Sorting Processing

• Plastic is collected
• It is then held in "dirty side bulk storage" (most likely spread on tarps)
• It is then photographed to easily document composition/type of products for data gathering purposes
• It is then rinsed in water, cleaned with soap water, then rinsed to remove general dirt and salts
• Then it is shredded
• Then it is moved on "pre-sorted clean bluk storage"

Sorting

• First the plastic flakes are dumped into a container containing water (DI not needed, but will very "hard water" effect the process?)
• 1,3, 6 sink and 2, 4, 5 float
• Then the streams are seperated (should manual batch skimming, then lifting up a bag/seive from the base be used, ***or*** , some sort of scaled down continous system be used?)

External Links

• A VERY simple lab on the process (middle school grade, but shows the concept, and uses common fluids (ie not wetting agents etc) )
• A Libretexts lab on this, has a great density table of common "pure" plastics
• A Page on the Densities of Various Alchohols (need to make a page on this)
• A Simon Fraser University Page on the Density of Common Fluids
• An "engineering toolbox" page on liquid densities
• "Recycling of plastic waste by density separation: Prospects for optimization"
• "Separation of waste plastics by froth flotation - A review, part I"
• "2 - Techniques for separation of plastic wastes"
• "Combination of three-stage sink–float method and selective flotation technique for separation of mixed post-consumer plastic waste"