Preparation of hydrophobic and lipophilic carboxymethyl cellulose composite aerogel using ferrous ion/ persulfate and its directed oxidation for oil-water emulsion separation

In particular, efficient oxidative demulsification is an effective method for oil-water separation. However, the inactivation of free radicals owing to the rapid release of transition metals is the main factor that reduces the effectiveness. In this study, a hydrophobic and lipophilic CP/SiO₂@Fe²⁺ composite aerogel was prepared using carboxymethyl cellulose as substrate, polyvinyl alcohol as reinforcement, and SiO₂ nanoparticles as hydrophobic modifier. The resulting aerogel had a water contact angle of 139°, oil absorption yield of 99.9 %, higher specific surface area 132.13 m²·g^-1, low density of 0.021 g·cm^-3, and high porosity of 98.60 %. Fe²⁺ was slowly released from the composite aerogel after efficient Fe²⁺ loading of 65.77 mg·g^-1. The drug exhibited a low release rate of 87.72 % after 9 h, which was higher than that of the composite aerogel. This promoted the efficient presence of SO₄^-· activated from persulfate oxidation in the catalytic oxidative demulsification system over a long period. The green and efficient separation of oily-water was achieved by the synergistic effect of the adsorption of the hydrophobic and lipophilic composite aerogel and targeted and efficient oxidative demulsification. These results demonstrate the advantages of high separation efficiency, durability, stability of the CP/SiO₂@Fe²⁺ composite aerogel for oil-water separation.