Silica xerogel derived from fly ash was synthesized and subsequently functionalized with ethylenediamine (EDA) and Cu²⁺ ions to produce a renewable hybrid adsorbent (SiO₂@NH₂–Cu) aimed at enhancing heavy metal removal from aqueous systems. The integrated process—comprising acid leaching, alkaline extraction, sol–gel gelation, and sequential organic/metal functionalization—successfully transformed crystalline fly ash into a high-purity amorphous silica framework. Acid activation increased SiO₂ content from 32.867 to 46.016 mg/kg, while the final xerogel achieved 71.053 mg/kg, confirming efficient impurity removal and silica enrichment. FTIR analysis verified the incorporation of –NH₂ and –CH₂ groups, while EDS revealed 0.46 wt% Cu, indicating effective metal anchoring onto the amine-functionalized silica surface. Textural analysis showed a mesoporous architecture with a surface area of 77.42 m²/g, a pore volume of 0.3894 cm³/g, and an average pore diameter of 16.09 nm, demonstrating substantial pore expansion following functionalization. FESEM imaging further revealed uniform morphology and homogeneous Cu distribution. An Artificial Neural Network (ANN) model was developed to predict adsorption performance based on structural and surface chemistry parameters, including pore size, –NH₂ group density, and Cu loading. Sensitivity analysis confirmed these parameters as the dominant contributors to adsorption efficiency. The combined experimental–computational approach highlights the synergistic role of EDA and Cu²⁺ in enhancing surface reactivity, establishing SiO₂@NH₂–Cu as a promising low-cost, sustainable adsorbent for wastewater treatment and related environmental applications.