Green Design and Theoretical Validation of A Novel Anthraquinone-Based Silica Sorbent for Selective Extraction of Pb(II) and Cd(II) from Brackish Aquaculture Water

In this study, a novel silica-supported sorbent functionalized with 1,4-bis[(4-methoxybenzyl) oxy]anthracene-9,10-dione was prepared and applied for the first time for the selective adsorption and preconcentration of Pb(II) and Cd(II) ions from brackish aquaculture water. The sorbent was characterized by FT-IR, ¹H NMR, and SEM-EDX, while kinetic modeling revealed that the adsorption process follows a pseudo-second-order kinetic model (R² > 0.999), indicating chemisorption-like kinetics for the rate-controlling step. Experimental parameters (pH, sorbent dosage, contact time, and temperature) were optimized using the one-factor-at-a-time (OFAT) approach and statistically validated via one-way ANOVA. Under optimal conditions (pH 6.0, 4 mg, 15 min), the method achieved high recoveries (96–99%), low detection limits (Pb: 1.5 µg/L; Cd: 1.6 µg/L), and excellent precision (RSD <2%). Matrix effect studies demonstrated the robustness and reliability of the method, showing <10% signal suppression and maintaining strong selectivity even in the presence of common coexisting ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, Fe³⁺, Zn²⁺). The sorbent preserved more than 90% of its adsorption capacity after five reuse cycles, indicating excellent stability and reusability. DFT analysis supported experimental findings, revealing a reduced HOMO–LUMO energy gap and stronger Pb(II)–ligand interactions, confirming the sorbent’s superior affinity toward Pb(II). Green analytical assessment (Eco-Scale: 82, AGREE: 0.87, GAPI: predominantly green profile) verified the method’s environmental compatibility, highlighting its minimal solvent use, low energy demand, and short analysis time. Overall, this study presents a selective, robust, reusable, and environmentally sustainable analytical method, introducing a new silica-based sorbent that effectively integrates experimental performance and theoretical validation for trace-level determination of Pb(II) and Cd(II).