Sulfonation method for efficient scaleup synthesis of Janus carbon nanofluids from waste plastics

A method of preparing an enhanced oil recovery composition comprising:

• carbonizing a waste plastic material to provide carbon microparticles;
• functionalizing the carbon microparticles with an SO3-containing gas such that the carbon microparticles comprise a hydrophilic surface, wherein functionalizing the carbon microparticles with the SO3-containing gas comprises heating the carbon microparticles at a temperature from about 30 to 70° C. at a flow rate from 0.1 milliliter per minute (mL/min) to 1 ml/min;
• and
• grinding the carbon microparticles to provide carbon nanoparticles, wherein the carbon nanoparticles comprise a hydrophilic surface and a hydrophobic surface.