Rate-Controlled Washing of Surface-Modified Nanoparticles Using Rationally Designed Supercritical CO₂ Media.

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Surface-modified nanoparticles (NPs) require efficient washing, but current methods face challenges like long treatment times and waste generation.
• Traditional washing methods for NPs can be inefficient, time-consuming, and environmentally burdensome.

Purpose of the Study:

• To develop a rapid and eco-friendly washing guideline for surface-modified NPs using cosolvent-enhanced supercritical CO2 (scCO2).
• To investigate the kinetics of NP washing using ethanol-enhanced scCO2 and understand the influence of modifier solubility.

Main Methods:

• Kinetic analysis of oleic acid-modified NPs washed with ethanol-enhanced scCO2 at 40 °C and 20.0 MPa.
• Systematic design of scCO2 media based on estimated solubilities of various fatty acid modifiers (C10-C18).

Main Results:

• Ethanol-enhanced scCO2 demonstrated superior washing rates compared to ethanol alone for diverse modifiers.
• Washing rates were found to be dependent on modifier solubility in scCO2, exhibiting two distinct control regions.
• A solubility threshold of 0.016 mol kg-1 was identified, differentiating solubility/diffusivity-controlled and diffusivity-controlled washing regimes.

Conclusions:

• Cosolvent-enhanced scCO2 provides an effective and rapid alternative for washing surface-modified NPs.
• The study offers valuable guidelines for optimizing scCO2 washing processes by considering modifier solubility and diffusivity.
• This approach facilitates complete, rapid, and eco-friendly purification of NPs, addressing current practical challenges.