Waste Banana Peels as a Precursor for the Synthesis of Elemental-Doped Silicon Quantum Dots Embedded in Silica for Efficient Adsorptive Decontamination of Textile Wastewater

Abstract

This study reports the synthesis, characterization, and application of element-doped silicon quantum dots (SiQDs) embedded in a silica (SiO₂) matrix for the adsorptive decontamination of textile wastewater. The nanocomposite was synthesized using a solution-based route from banana-derived precursors, producing nanoparticles with a high silica content (SiO₂: 73.25 wt.%, 78.07 mol.%) and trace dopants including Fe₂O₃ (3.56 wt.%), Al₂O₃ (7.16 wt.%), K₂O (4.11 wt.%), and Na (18.6 at.%). UV–visible spectroscopy revealed strong absorption in the 200–300 nm range, with an estimated bandgap of 3.5–4.5 eV, confirming the wide bandgap nature of the material. FTIR analysis identified characteristic Si-O-Si and Si-OH vibrations at 1027.43, 443.26, 475.76, and 3347.43 cm⁻¹, indicating a polymerized silicate network with surface hydroxyl groups. XRD analysis confirmed partial crystallinity (Xc = 23.92°) with nanosized crystallites (~0.40 nm), while SEM images showed a porous, fibrous morphology suitable for adsorption. The adsorption performance of the SiQDs@SiO₂ nanocomposite was evaluated against a model textile dye. The removal efficiency increased rapidly, reaching 83.11% within 60 min and 89.86% at 120 min. High removal efficiencies were observed across initial dye concentrations of 10–50 mg/L (81.42–83.11%), with optimal adsorbent dosage (1.0 g/100 mL) achieving 91.89% removal. pH-dependent studies revealed maximum decontamination at pH 9 (87.16%). The superior performance is attributed to the nanoscale size, high surface-to-volume ratio, defect-rich structure from elemental doping, and the stabilizing silica matrix, which prevented agglomeration and provided additional active sites for electrostatic interactions and hydrogen bonding. the study demonstrates that doped SiQDs embedded in silica are highly effective, stable, and versatile nanomaterials for textile wastewater treatment, offering removal efficiencies above 89% under optimized conditions and strong potential for practical environmental remediation applications