Rapid industrialization and urbanization have led to significant environmental challenges, particularly the contamination of water bodies by contaminants of emerging concern (CECs) due to insufficient tertiary treatment in wastewater treatment plants (WWTPs). Pharmaceuticals like acetaminophen (ACT) and sulfamethoxazole (SMX), as well as phenolic compounds like gallic acid (GA), are persist and bioaccumulate, posing risks to water quality. This study explores the development of permeable reactive barriers (PRBs) using eco-friendly materials: geopolymers (GP), activated carbon (AC), and carbon nanotubes (CNT), sourced from waste. Integrating these materials into PRBs aligns with circular economy principles, providing a
sustainable solution to reduce exposure to contaminated water. Elemental analysis revealed that AC contained 63.0% carbon, while CNT exhibited a higher carbon content of 92.5%. The GP analysis indicated substantial calcium and silicon content, and structural analysis via X-ray diffraction (XRD) identified key crystalline phases, predominantly calcite. Functional characterization using Fourier-transform infrared spectroscopy (FT-IR) confirmed the presence of hydroxyl and carbonyl groups in AC and notable C–O bonds in CNTs. Additionally, acid-base characterization demonstrated AC's high basicity (1250 μmol/g), enhancing its capacity to adsorb acidic compounds. Morphological studies using SEM and TEM illustrated the
heterogeneous structure of GP and the arrangement of CNTs, including iron nanoparticles, from the synthesis process. BET analysis revealed AC’s superior specific surface area (527 m²/g) and pore volume (0.313 cm³/g) compared to CNT (66 m²/g) and GP (30 m²/g), enhancing its adsorption capacity. Equilibrium analysis revealed that the Freundlich model effectively described the adsorption process, indicating favorable conditions and a strong affinity between adsorbates and adsorbents. The maximum adsorption capacities of AC were determined using the Langmuir model, with values of 112.19 mg/g for ACT, 40.25 mg/g for SMX, and 314.27 mg/g for GA. Kinetic studies confirmed that all materials followed a pseudo-second-order model, achieving equilibrium within approximately 50 minutes. Continuous flow experiments validated the batch adsorption results, showing the effective performance of AC and GP, with breakthrough capacities of 126.85 mg/g for ACT, 54.93 mg/g for SMX, and 151.53 mg/g for GA. Breakthrough times were recorded at 314 minutes for ACT, 66 minutes for SMX, and 68 minutes for GA. The multi-component system exhibited similar behavior, although saturation occurred earlier.
