Dynamic absorption of heavy metal from aqueous solution using lignin-hydrogel and natural filter materials in a...

Static adsorption methods, despite their utility in specific scenarios, face numerous challenges such as limited contact time, adsorbent saturation, inefficient mass transfer, scalability constraints, and operational downtime. To address these limitations, this study developed a packed column system for the dynamic adsorption of heavy metal ions, specifically Pb(II), from aqueous solutions. The system employs two advanced adsorbents: partially hydrolyzed acrylamide-grafted alkali-lignin hydrogel (AM-g-AL) and a composite blend of Fuller's earth, carboxymethylcellulose, and activated carbon (FE-CMC-AC). Comprehensive characterization of the adsorbents was performed using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) with mapping. The adsorption performance of both materials was evaluated under diverse operating conditions. AM-g-AL demonstrated a notable adsorption capacity of 111.20 mg/g for Pb(II), while the FE-CMC-AC composite exhibited a superior capacity of 278.45 mg/g. Adsorption equilibrium data for both adsorbents conformed to the Freundlich isotherm model, and column adsorption data were effectively modeled using the Thomas and Yoon-Nelson models. The packed column system achieved a cumulative adsorption capacity of 476.75 mg/g for Pb(II) during continuous operation, underscoring its efficacy at the pH range 6-8. This study highlights the potential of packed column systems over traditional batch processes or single adsorbents for the efficient and scalable removal of Pb(II) from water, offering a promising pathway for industrial and environmental applications.