Sustainable Synthesis of Zn-Doped Silica Nanocomposites from Waste Silica Gel for Enhanced Methylene Blue Adsorption and Antimicrobial Activity

 

Abstract

This study reports the valorization of waste silica gel (60–200 mesh) into silica nanoparticles (SiO₂ NPs) and zinc-doped silica nanocomposites (Zn–SiO₂ NCs) for wastewater remediation. Comprehensive characterization (SEM, EDX, FTIR, and XRD) confirmed the nanoscale structure and successful incorporation of Zn. Both materials efficiently removed methylene blue (MB), with Zn-SiO₂ NCs exhibiting slightly higher adsorption capacity (9.59 mg/g) compared to SiO₂ NPs (9.23 mg/g) under optimal conditions (pH 7, 30 min contact time, 10 mg/L MB). Adsorption behavior followed the Temkin isotherm, suggesting uniform active sites and moderate adsorbate–adsorbent interactions. Kinetic data were best described by the pseudo-second-order model, indicating surface-controlled uptake, while thermodynamic analysis (ΔH values within the physisorption range) confirmed that the process is predominantly governed by physical adsorption. This aligns with a mechanism dominated by rapid surface interactions. Both adsorbents retained over 85% efficiency after four regeneration cycles. Furthermore, Zn-SiO₂ NCs exhibited pronounced antimicrobial activity, producing inhibition zones of 12–14 mm against Escherichia coli, Bacillus sp., Enterococcus ATCC, and Candida albicans. Overall, this work highlights the sustainable transformation of silica waste into multifunctional nanomaterials with dual applications in dye removal and microbial control, contributing to circular economy strategies.

 

Link: https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/slct.202503661