Unveiling the superior adsorptive performance and stability of mushroom-derived biochar for the removal of p-aminoazobenzene from real and synthetic water samples: Insights from experiments and simulations

The efficient elimination of p-aminoazobenzene (p-AAB), an aromatic amine contaminant, from water remains a major environmental challenge due to the low adsorption efficiency of conventional adsorbents. In this work, a sustainable mushroom-derived biochar (MDB) synthesized from waste biomass was developed and assessed as a promising adsorbent for p-AAB removal from both real and synthetic water samples. A range of adsorbents, including raw mushroom powder, mushroom/ZnO₂ composite, Fe/Mn mixed oxides, chitosan, and chitosan-based mixed oxide composites, were evaluated, among which MDB exhibited the highest adsorption capacity (99.14%) which was significantly higher than those of raw mushroom powder (60.4%), chitosan (69.4%), and Fe/Mn mixed oxides (62.5%). The impact of co-existing ions was also investigated to assess the selectivity and stability of MDB in complex multi-ion environments. Furthermore, multi-dye adsorption tests using p-AAB and other dyes confirmed the broad-spectrum adsorption ability of MDB. Mass loss analysis revealed excellent structural integrity and physical stability during successive adsorption–desorption cycles. XPS and FTIR analyses indicated that carbon-, nitrogen-, and oxygen-containing functional groups were primarily responsible for adsorption through π–π interactions, hydrogen bonding, and electrostatic forces. Density Functional Theory (DFT) calculations were performed, confirming strong interaction energies between p-AAB molecules and the functional groups on MDB, consistent with experimental results. Regeneration experiments showed that MDB retained about 70% of its initial efficiency after five cycles, demonstrating good reusability. Overall, the findings highlight MDB as an eco-friendly, durable, and high-performance biosorbent for the removal of aromatic amines from both real and synthetic wastewater samples. • Mushroom-derived biochar (MDB) showed superior adsorption capacity for aromatic amine p-aminoazobenzene (p-AAB). • Real wastewater samples from industrial effluents were effectively treated, achieving nearly complete p-AAB removal. • π–π interactions, hydrogen bonding, and electrostatic forces governed the adsorption mechanism. • DFT calculations confirmed strong binding energies between MDB and p-AAB molecules. • MDB exhibited high reusability and maintained ~70% efficiency after five adsorption–desorption cycles.