Facile and eco‐friendly fabrication of hierarchical superhydrophobic coating from eggshell biowaste

Abstract This study reports a facile and sustainable approach to fabricate superhydrophobic coating from eggshell biowaste. The coating was prepared by ball milling chicken eggshells, composed of hydrophilic calcium carbonate (Ca CO 3 ), to microsized particles followed by surface hydrophobilizing with stearic acid (C 17 H 35 COOH ) to form low surface energy nanosized calcium stearate ((C 17 H 35 COO ) 2 Ca) through the esterification of hydroxyl groups (‐ OH ) absorbed on a surface of Ca CO 3 with carboxyl groups (– COOH ) of stearic acid. Then, a layer of modified eggshell particles dispersed in polystyrene ( PS ) binder was dip‐coated on a substrate. A coated surface with water contact angles of 151° ± 1° on glass and 153° ± 1° on cotton fabric substrates was achieved when a 4:1 weight ratio of the modified eggshell: PS was used. The uniform distribution of the modified eggshell particles throughout the coating led to a surface with high degree of hierarchical micro‐nanoscale roughness which resulted in superhydrophobicity. The superhydrophobic eggshell coating showed good environmental stability, self‐cleaning, and oil/water separation properties. These results suggest that eggshell biowaste can be utilized for superhydrophobic applications.