Superhydrophobic SiO2 microspheres of a porous dehydroabietic-acid-based homopolymer for oil–water separation

Abstract

The contamination of water with fat-soluble organic pollutants poses a significant threat to human health and requires effective removal methods. Superhydrophobic materials can adsorb oil from water and separate oil–water mixtures. Therefore, we prepared superhydrophobic microspheres by grafting a homopolymer of dehydroabietic acid (DAG) on porous silica. The DAG was synthesized from rosin, a natural material, and then grafted onto bromo-modified silica by atom transfer radical polymerization (ATRP). In addition, the DAG dosage and ATRP conditions were varied to control the grafting amount and polymer molecular weight. The synthesized microspheres, denoted (SiO2-g-PDAG), were then characterized by thermogravimetric analysis, Brunauer–Emmett–Teller analysis, gel permeation chromatography, contact angle measurements, and scanning electron microscopy. The microspheres had a water contact angle of 169.4° and grafting amount of 39.0 wt%. With the addition of DAG, the hydrophobic properties of the microspheres and the adsorption properties of the toluene-in-water emulsion were significantly improved. Further, the contact angle increased and specific surface area and pore size decreased with the increase in polymer molecular weight. Crucially, the microspheres showed high adsorption capacity (7.78 g⋅g−1) and removal rate (99.2 %) for a toluene-in-water emulsion. They also showed good separation performance for oil–water mixtures and good stability and superhydrophobicity after ultrasonic vibration and soaking in different solvents. In summary, the SiO2-g-PDAG microspheres are promising adsorbents for environmental remediation.