Base- or acid-assisted polystyrene plastic degradation in supercritical CO₂

Area of Science:

• Environmental Chemistry
• Materials Science
• Chemical Engineering

Background:

• Plastic pollution, particularly from polystyrene (PS), poses a significant environmental challenge due to its inert nature.
• Supercritical fluids, like carbon dioxide (CO2), exhibit unique properties beneficial for various applications, including material degradation.
• Developing efficient methods for polystyrene degradation is crucial for mitigating plastic waste and its environmental impact.

Purpose of the Study:

• To investigate the degradation of polystyrene (PS) using supercritical carbon dioxide (Sc-CO2) under mild conditions.
• To evaluate the effectiveness of NaOH/HCl solutions as auxiliary agents in enhancing PS degradation within Sc-CO2.
• To model and optimize the degradation process using response surface methodology (RSM).

Main Methods:

• Polystyrene (PS) degradation was conducted using supercritical CO2 (Sc-CO2) assisted by NaOH/HCl solutions.
• Response surface methodology (RSM) was employed to design the reaction model and identify optimal parameters.
• Key factors influencing degradation efficiency, including temperature, time, and base/acid concentration, were systematically studied.

Main Results:

• Optimal degradation conditions (400°C, 120 min, 5% NaOH/HCl) yielded significant gas production and CO2 consumption.
• Sc-CO2 facilitated a homogeneous reaction environment, promoting PS dispersion and uniform heating for enhanced degradation.
• The addition of NaOH/HCl improved PS solubility in Sc-CO2 and reduced activation energy, boosting degradation efficiency.

Conclusions:

• Degrading polystyrene in supercritical CO2 is a feasible and effective method for plastic waste treatment.
• Assistance from base/acid solutions significantly enhances PS degradation efficiency in Sc-CO2.
• This approach provides a valuable reference for future waste plastic disposal strategies.