Abstract
In this study, a novel geopolymer-based nepheline–cordierite composite was synthesized and evaluated as an efficient adsorbent for the removal of cytotoxic tamoxifen from aqueous solutions. The maximum removal efficiency of 96.08 % was achieved under optimal conditions: 40 mg/L tamoxifen concentration, 80 mg adsorbent dose, pH 7, 150 min of contact time, and 298 K. Adsorption kinetics were best described by the pseudo-second-order model (R 2 = 0.998), suggesting that chemisorption is the dominant mechanism. Equilibrium data were best fitted to the Langmuir isotherm model (R 2 = 0.996), indicating monolayer adsorption on a homogeneous surface. Thermodynamic parameters (ΔG° < 0, ΔH° = +48.267 kJ/mol, ΔS° = +174.568 J/mol·K) revealed that the adsorption process is spontaneous and endothermic. The pH at the point of zero charge (pHpzc) was determined to be 7.03, supporting the effectiveness of adsorption near neutral pH. Characterization of the adsorbent using BET, XRD, FTIR, and SEM analyses confirmed its porous structure, high surface area, and functional groups favorable for tamoxifen interaction. These findings suggest that the synthesized geopolymer-based nepheline–cordierite material is a promising, cost-effective, and environmentally friendly adsorbent for removing pharmaceutical contaminants from water.