Unlocking the potential of waste: eggshell-based CaCO₃ nanoparticles for functional applications of polymeric materials

Due to the increasing environmental pollution caused by synthetic plastics, particularly in Mexico, there has been growing interest in the development of sustainable materials derived from biopolymers and agri-food waste. This research evaluated the use of eggshell nanoparticles (ENPs), which are rich in calcium carbonate, as functional reinforcements in various polymeric matrices. ENPs were obtained through high-energy milling for periods of 1–3 h, reaching an average size of 84 ± 40 nm after 2 h, with 91 % of the particles < 100 nm. These nanoparticles were incorporated at concentrations of 1–3 wt.% into gellan gum (GG) films intended for the manufacture of compostable utensils and were also blended with polylactic acid (PLA) to produce filaments processed by extrusion. Additionally, superhydrophobic coatings inspired by the lotus leaf effect were developed by applying ENP and ZnO micro- and nanoparticles onto glass substrates. The materials were characterized using optical, confocal, and electron microscopy, as well as FTIR, XRD, and texture image analysis. The results for the films showed that the incorporation of 3 % ENPs into GG significantly improved their mechanical, thermal, and hydrophobic properties; in the filaments, it was observed that 2 % ENP supports flexibility. On the other hand, the coatings with the highest surface roughness were those in which ENP was used with ZnO nanoparticles with contact angles > 150°, confirming its superhydrophobic character. Overall, these results demonstrate that the use of waste materials such as eggshells enables the development of biodegradable materials with enhanced functional properties and potential applications in packaging, utensils, and surface treatments, contributing to a circular economy and reducing the environmental impact of conventional plastics.