Innovative preparation of multi-dentate Schiff base adsorbent for the adsorption of silver and its application on nano silver particles preparation from liquid photographic wastes

Abstract

BACKGROUND

A novel silver adsorbent, (2Z,2′ E)-2,2′-((1,10-phenanthroline-2,9-diyl)bis(methaneylylidene))bis(N-phenylhydrazine-1-carboxamide) (PHMC), was synthesized for efficient Ag⁺ adsorption. PHMC was prepared by refluxing 1,10-phenanthroline-2,9-dicarboxaldehyde with N-phenylhydrazinecarboxamide at 120 °C. The structural and morphological properties of PHMC were characterized using various analytical techniques including FTIR, SEM, BET surface area analysis, ¹³CNMR, ¹HNMR, and GC–MS, to confirm the formation of PHMC adsorbent.

RESULTS

The results demonstrated that PHMC possesses an exceptional silver sorption capacity of 440.67 mg g⁻¹ in aqueous solutions. Additionally, PHMC exhibited excellent reusability, with effective desorption of Ag(I) using a 1 M thiourea solution, enabling adsorbent regeneration. The adsorption of Ag⁺ onto PHMC was well described by Langmuir and D-R isotherms, as well as pseudo-second order and intraparticle diffusion (IPD) kinetic models. PHMC showed remarkable selectivity for silver, even in the presence of competing ions, and demonstrated significant stability, retaining over 95% of its initial capacity after four regeneration cycles and more than 80% after seven cycles. Thermodynamic investigations revealed that the sorption process was endothermic.

CONCLUSION

PHMC proved to be a highly effective adsorbent for silver removal, with superior reusability compared to other materials. Optimal adsorption conditions were established for the removal of silver from liquid photographic waste. The recovered silver nitrate was successfully used to synthesize Ag nanoparticles using trisodium citrate (TSC) as a reducing agent, and the resulting nanoparticles were characterized using various analytical techniques to confirm the formation of silver nanoparticles. © 2024 Society of Chemical Industry (SCI).