Removal of cytotoxic tamoxifen from aqueous solutions with geopolymer-based nepheline/cordierite adsorbent

Increasing pharmaceutical pollution poses a significant threat to the protection of water resources. Tamoxifen, a widely used anticarcinogenic drug, is among the pharmaceutical residues in wastewater, causing environmental damage. In this study, porous geopolymer material was produced and used as adsorbent for the removal of tamoxifen from aqueous solutions. The produced geopolymer adsorbent material was characterized in detail by BET, SEM and FTIR analysis. During the adsorption process, various parameters such as initial tamoxifen concentration (10-60 μg/mL), pH value of the solution (4-10), adsorbent amount (20-100 mg per 50 mL solution), contact time (0-180 min) and temperature (298-318 K) were evaluated and the optimum conditions were determined. Kinetic analyses were performed with pseudo-first and second order models and the equilibrium state was investigated with Langmuir and Freundlich isotherm models. As a result of the calculation of thermodynamic parameters, it was determined that maximum removal efficiency of 96.08% was achieved under optimum conditions (40 μg/mL initial concentration, 80 mg adsorbent dose, 150 minutes contact time, pH 7). The adsorption process was best described by the pseudo-second order kinetic model (R²: 0.9999) and Langmuir isotherm model (R²: 0.9957). Moreover, thermodynamic analyses have shown that the process is spontaneous (ΔG < 0), exothermic (ΔH < 0) and causes a decrease in disorder in the system (ΔS < 0). This study demonstrates the potential of using geopolymer adsorbent as an environmentally friendly and economical treatment method.