Sustainable Ca-TiO2 paper platforms: exploiting eggshell biowaste for environmental remediation

Abstract

Sustainable photocatalysis has emerged as a promising approach for environmental remediation by combining efficiency with green chemistry principles. In this study, Ca-TiO₂ photocatalytic platforms were developed using cellulose paper as a substrate, calcium sourced directly from eggshell biowaste, and a sustainable microwave-assisted synthesis approach. A novel functionalization of the Whatman paper preserved its structural integrity at temperatures above 200 °C, enabling the direct growth of TiO₂ nanomaterials on paper substrate without any post-synthesis treatment. Incorporation of bio-derived Ca²⁺ modified the TiO₂ structure, inducing structural defects that included lattice distortions, voids, and surface step sites, modifying optical absorption, and enhancing surface hydroxylation. The resulting Ca-TiO₂ paper-based platforms efficiently degraded tetracycline, achieving over 80% removal under solar irradiation in 150 minutes, corresponding to a photodegradation rate 1.3 times higher than that of pure TiO₂. Reusability and ecotoxicity tests confirmed their stability and safety for long-term environmental applications. By integrating waste valorization, green synthesis, and structural modifications, this work demonstrates a sustainable and scalable strategy for producing high-performance photocatalytic platforms, aligning with circular economy principles and offering potential solutions for global water pollution challenges.