Optimized removal of methylene blue from wastewater using an activated Carbon-Zinc Oxide-Ammonia composite

This study systematically investigates the adsorption and degradation of methylene blue (MB) dye from wastewater using an activated carbon-zinc oxide-ammonia (AC-ZnO-NH₃) composite. The composite was synthesized through ammonia doping and integration of zinc oxide nanoparticles, enhancing its adsorption and catalytic capabilities. Batch experiments revealed optimal conditions for MB removal at pH 9, 50 ppm dye concentration, and a contact time of 180 min, achieving 97.4%removal efficiency. Kinetic studies indicated that the adsorption followed pseudo-second-order kinetics (R² = 0.998), typically suggesting chemisorption. However, mechanistic investigations-supported by FTIR, SEM, and zeta potential analysis-revealed that MB removal was primarily driven by strong electrostatic interactions, π-π stacking, hydrogen bonding, and photocatalytic degradation. This suggests a hybrid mechanism involving both physisorption and chemisorption pathways. Isotherm analysis confirmed the Langmuir model's suitability ([Formula: see text]), with a maximum monolayer adsorption capacity of 106.38 mg/g. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) confirmed the functional groups and porous morphology responsible for adsorption. Furthermore, a cost analysis indicated that the AC-ZnO-NH₃ composite is economically viable for both small- and large-scale wastewater treatment applications, reinforcing its scalability, multifunctionality, and environmental compatibility. This cost-effective and eco-friendly composite provides a promising solution for treating dye-contaminated wastewater, emphasizing its scalability and multifunctionality in environmental remediation.