Modified biochar (BC) nano-compounds are very promising candidates for the accelerated degradation of reoccurring contaminants in wastewater treatment. The surface activity, structural repair, and dopant chemistry of biochar determine its adsorption ability and catalytic behaviour. Metal oxides such as Fe₃O₄ and FeS₂ offer fast electron-transfer pathways that accelerate the redox-mediated transformations of heavy metal ions, while surface-engineered functional groups, particularly phosphorus moieties and EDTA ligands, provide tunable coordination environments that significantly enhance selectivity toward Pb²⁺ and Ni²⁺. Chemical activators such as ZnCl₂ and KOH introduce hierarchical porosity and widen the distribution of adsorption sites, thereby improving the reactant accessibility and charge-transfer efficiency. Layered double hydroxides (Ni–Fe and Mg–Al) exhibit structurally defined anion-exchange galleries that preferentially interact with oxyanions (PO₄ ³⁻ and NO₃ ⁻), whereas heteroatom-doped biochars (S/N-BC) generate polarized electron densities favourable for binding soft metal ions such as Hg²⁺ and Cu²⁺. Additionally, carbonaceous nanostructures (CNTs and graphene oxide) enable π–π stacking and delocalized electron mediation for the sensitive detection and transformation of aromatic dye molecules. From a materials chemistry perspective, the innovation lies in tailoring these nano-hybrids at the atomic-to-nano scale, optimizing their mechanical stability, interfacial charge dynamics, and metal–support interactions while comprehensively evaluating their structural persistence and catalytic fidelity under realistic aqueous reaction conditions. AI-directed designs aid in performance optimization. Finally, identifying research gaps, optimizing benefit circulation, and conducting comprehensive life cycle assessment (LCA) are crucial for the effective implementation of these concepts. In this review, these aspects are systematically discussed and highlighted to guide future research directions for the next generation of studies.

In the present investigation, the corrosion tendency of mild steel under acidic pH was studied by employing unused expired amiodarone (EAD) drug as a potential corrosion inhibitor by adopting the weight loss measurement method. The corrosion inhibition efficiency (IE) of the formed protective film (EAD) on the steel surface was analyzed using potentiodynamic polarization and AC-impedance spectroscopy studies. The surface morphology of the mild steel before and after corrosion (in 1.0 M HCl) was analyzed via scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDAX), atomic force microscopy (AFM), and thermodynamic studies. The weight loss measurement under different concentrations of EAD indicated that an excellent inhibition was displayed at a concentration of 0.001 M, and the IE was found to depend on both the concentration and molecular structure of EAD. A potentiodynamic polarization study revealed that EAD predominantly acted as a cathode inhibitor, and electrochemical impedance spectroscopy (EIS) confirmed the adsorption of EAD on the surface of mild steel, which obeyed Temkin’s adsorption isotherm model. The calculated thermodynamic parameters revealed that adsorption was spontaneous and exothermic.

Till now Mg-based alloys have attracted much attention due to the high storage capacity of hydrogen. An effort was made to evaluate the apparent activation energy and electrochemical behavior of transition metals such as scandium (Sc), zirconium (Zr), and niobium (Nb) alloyed with Mg–Ti. Mg_0.8Ti_0.2, Mg_0.6Ti_0.2Sc_0.2, Mg_0.6Ti_0.2Zr_0.2, and Mg_0.6Ti_0.2Nb_0.2 alloy powders were synthesized using high-energy ball milling. Ballmilled powders were subjected to structural and morphological characterization using X-ray diffraction and scanning electron microscopy respectively. A strong shift in the inter-planar spacing value of milled powders confirmed supersaturated solid solution of Ti and transition metals in Mg. The inter-planar spacing values before and after milling are found to be 0.24 and 0.21 nm, respectively. Mg_0.8Ti_0.2, Mg_0.6Ti_0.2Sc_0.2, and Mg_0.6Ti_0.2Zr_0.2 alloy powders result in the FCC phase while Mg_0.6Ti_0.2Nb_0.2 powders result in BCC phase, however, the entire powders have an amorphous background. SEM-EDS analysis of the milled powders confirmed the presence of Mg, Ti, Sc, Zr, and Nb elements with a small amount of oxygen. Selected area electron diffraction (SAED) pattern of Mg_0.8Ti_0.2 alloy powders exhibits a nanocrystalline nature owing to their polycrystalline ring pattern. Exothermic peak broadening increases after the substitution of Nb and Zr in Mg_0.8Ti_0.2 alloy powder, which exhibits a lower activation energy (188 kJ mol⁻¹) than others. In cyclic voltammetry, a drenched cathodic peak is observed for Mg_0.8Ti_0.2 at a potential around −0.83 V. In electrochemical impedance spectroscopy, the charge transfer resistance of Mg_0.6Ti_0.2Sc_0.2 is lower than that of Mg_0.6Ti_0.2Zr_0.2 and Mg_0.6Ti_0.2Nb_0.2 alloy but higher than Mg_0.8Ti_0.2 electrode materials, and charge–discharge studies were done on the developed electrode materials. It shows that Mg_0.8Ti_0.2 electrode material delivers a maximum discharge capacity of 535 mA h g⁻¹.