Eco-Friendly Copper Adsorption by a Novel Bis-Aminophosphonate: Design, Synthesis, Equilibrium, and Bioactive Applications

A novel composite material, pyridyl-bis-aminophosphonate derivative (Pyph), was successfully synthesized via a high-yield reaction involving pyridine-2,6-dialdehyde and N,N'-diphenyl thiosemicarbazide. This innovative material exhibits exceptional potential for the efficient removal of Cu²⁺ ions from both drinking and wastewater, as confirmed through rigorous analytical techniques. A comprehensive optimization study was conducted to determine the optimal experimental conditions for maximum Cu²⁺ adsorption, including pH, equilibrium time, initial Cu²⁺ concentration, Pyph dosage, temperature, and eluting agent type. Notably, Pyph achieved a remarkable sorption capacity of 185 mg/g under optimal conditions: ambient temperature, pH 3.5, 10 min of agitation, and an initial Cu²⁺ concentration of 500 mg/L. Equilibrium isotherm analysis revealed a superior fit to the Langmuir model compared to the Freundlich model, predicting a maximum uptake capability of 185.18 mg/g, aligning closely with experimental observations. Kinetic studies further substantiated the adsorption process, with the pseudo-first order model accurately describing the adsorption behavior and predicting a theoretical sorption capacity of 186.33 mg/g. The Dubinin-Radushkevich (D-R) isotherm model provided insights into the adsorption mechanism, indicating chemisorption as the dominant process due to an adsorption energy (E) of 9.053 kJ/mol and a theoretical retention power of 186.6 mg/g. Thermodynamic evaluations indicated that the sorption process is exothermic, spontaneous, and favored at lower temperatures, emphasizing the material's efficient operation under ambient conditions. The efficient desorption of Cu²⁺ ions from the loaded Pyph was achieved using sulfuric acid (2 M ≈ 95% efficiency), hydrochloric acid (1.5 M ≈ 99%), and nitric acid (2 M ≈ 99%) as eluting agents, demonstrating a high level of elution efficacy. Importantly, Pyph's efficacy in removing Cu²⁺ ions from drinking water aligns with stringent safety standards set by the American Public Health Association (APHA), World Health Organization (WHO), Indian Standard Institution (ISI), Central Pollution Control Board (CPCB), and Indian Council of Medical Research (ICMR), ensuring safe drinking water after a single treatment cycle. Furthermore, the compound Pyph exhibits potent antioxidant and antibacterial properties, demonstrating efficacy against both Gram-negative (E. coli) and Gram-positive (B. subtilis) bacteria. This multi-faceted functionality positions Pyph as a promising and effective material for water purification and potential applications in the biomedical field.

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