PVC removal from mixed plastics by triboelectrostatic separation.

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Rising oil prices and plastic waste necessitate advanced recycling methods.
• Polyvinyl chloride (PVC) poses environmental hazards (HCl, dioxins) and hinders other plastic recycling.
• Current disposal methods like reclamation and incineration are problematic.

Purpose of the Study:

• To design and test a bench-scale triboelectrostatic separator for removing PVC from mixed plastics (PVC/PET).
• To optimize separation conditions for efficient PVC removal and PET recovery.
• To achieve high-purity polyethylene terephthalate (PET) recovery.

Main Methods:

• Utilized a fluidized-bed tribo charger to impart opposite charges to PVC (negative) and PET (positive) particles based on work function differences.
• Employed an electric field and a splitter for particle separation.
• Investigated the influence of tribo charger material, relative humidity, air velocity, and mixture ratio on charge efficiency.

Main Results:

• Optimal conditions (20 kV electrode potential, -2 cm splitter position) yielded 99.60% PVC rejection and 98.10% PET recovery.
• Separation efficiency was sensitive to tribo charger material (polypropylene), low relative humidity (<30%), high air velocity (>10 m/s), and a 1:1 PET:PVC ratio.
• Reproducibility of optimal tests was excellent (+/-1%).
• High-purity PET (>99.99%) was achievable by adjusting the splitter position, albeit with reduced overall PET recovery.

Conclusions:

• Triboelectrostatic separation is a viable method for efficiently removing PVC from mixed plastics.
• Optimized conditions ensure high PVC rejection and PET recovery, crucial for effective plastic recycling.
• The technique offers a pathway to producing high-purity recycled PET, enhancing its value and application potential.