α-aminophosphonate (α-AP) is used as a novel corrosion inhibitor for carbon steel. The aggressive media applied in this study are HCl and H₂SO₄ acid solutions. The findings indicate that the morphology of the α-AP compound is cubic, with particles ranging in size from 17 to 23 μm. FT-IR, ¹HNMR, ³¹PNMR, and ¹³CNMR analysis confirmed the synthesis of the α-AP molecule. It has been discovered that the compound α-AP plays an important role in inhibiting the corrosion of carbon steel in both HCl and H₂SO₄ acids. This was identifiably inferred from the fact that the addition of α-AP compound decreased the corrosion rate. It is important to report that the maximum inhibition efficiency (92.4% for HCl and 95.7% for H₂SO₄) was obtained at 180 ppm. The primary factor affecting the rate at which steel specimens corrode in acidic electrolytes is the tendency of α-AP compounds to adsorb on the surface of steel through their heteroatoms (O, N, and P). This was verified by SEM/EDX results. The adsorption actually occurs through physical and chemical mechanisms via different active centers which are matched with the calculated quantum parameters. In addition, the adsorption of α-AP follows the Langmuir isotherm.

Upcycling industrial aluminum waste into functional adsorbent materials offers a sustainable strategy for addressing complex wastewater contamination by coexisting organic dyes and toxic heavy metals. In this study, a waste-derived nano-Al₂O₃-loaded pyranopyrazole composite is rationally designed to enable high-capacity and simultaneous removal of methylene blue and Cd(II) ions from aqueous systems. The heteroatom-rich pyranopyrazole framework provides multiple organic binding domains, while nano-alumina incorporation introduces additional Al–O active sites and surface hydroxyl groups that collectively enhance interfacial adsorption efficiency. Comprehensive structural, spectroscopic, and microscopic characterization confirms homogeneous alumina anchoring and the formation of a stable organic–inorganic hybrid interface. The resulting composite exhibits markedly improved adsorption performance relative to the pristine pyranopyrazole, achieving maximum experimental uptake capacities of 189 mg g⁻¹ for methylene blue and 343 mg g⁻¹ for Cd(II) under optimized conditions. Adsorption kinetics follow a pseudo-second-order model, indicating surface-controlled chemisorption, while equilibrium data are best described by the Freundlich isotherm, reflecting adsorption on energetically heterogeneous surfaces. Thermodynamic analysis reveals that both adsorption processes are spontaneous and exothermic. Spectroscopic evidence combined with density functional theory calculations demonstrates that adsorption proceeds through synergistic coordination, electrostatic attraction, hydrogen bonding, and π-interactions involving nitrogen- and oxygen-donor sites of the organic framework together with alumina-derived Al–O centers. The composite maintains high removal efficiency over repeated adsorption–desorption cycles and exhibits effective performance in real wastewater matrices. Overall, this work establishes a clear structure–interaction–performance relationship for waste-derived alumina–organic hybrids and highlights their potential as sustainable, reusable, and multifunctional adsorbents for advanced water remediation targeting both organic dyes and heavy-metal contaminants.

A heteroatom-rich pyridine-based adsorbent (Pyridine PC) was synthesized through a multicomponent strategy and structurally confirmed by ¹H/¹³C NMR spectroscopy and mass spectrometry. To further enhance adsorption activity and surface reactivity, waste-derived CuO nanoparticles were immobilized onto the porous heterocyclic framework, generating a sustainable CuO@Pyridine PC hybrid nanocomposite. Batch adsorption experiments demonstrate highly efficient removal of malachite green (MG) dye and Cd(II) ions from aqueous solutions. Kinetic analysis reveals that adsorption follows the pseudo-second-order model, while equilibrium data are best described by the Freundlich isotherm, indicating adsorption on heterogeneous surfaces. Thermodynamic parameters confirm that the adsorption processes are spontaneous and exothermic. Surface and structural characterization using SEM/EDX, elemental mapping analysis and FT-IR before and after adsorption verifies strong pollutant binding and highlights the role of nitrogen- and oxygen-containing functional groups as dominant interaction sites. BET measurements show that CuO incorporation increases surface area and pore volume, while zeta potential analysis indicates excellent colloidal stability of the composite in aqueous media. Consequently, the CuO-modified sorbent exhibits enhanced adsorption capacities, increasing from 169.8 to 176.13 mg g⁻¹ for MG and from 276.5 to 368 mg g⁻¹ for Cd(II). The adsorbent demonstrated effective pollutant removal from real wastewater. The adsorption mechanism involves synergistic interactions between functional groups in the Pyridine PC matrix and CuO nanoparticles, providing enhanced active binding sites.

Thioctic acid, a sulfur-rich molecule, acts as an efficient and regenerable adsorbent for Cd( ii ), Pb( ii ), and Cu( ii ), with metal binding governed by strong S- and O-donor interactions.