High-efficiency heavy metal adsorption in complex systems via FeS-modified poly(acrylamide-co-2-acrylamido-2-methylpropane sulfonic acid)-g-carboxymethylcellulose-Ca(II) hydrogel

Composite adsorbent systems incorporating ferrous sulfide (FeS) nanoparticles stabilized within a mechanically durable hydrogel network exhibit notable potential for remediation of heavy metal-contaminated environments. However, their interfacial behaviors and synergistic mechanisms in multi-metal systems require deeper exploration. Herein, poly(acrylamide-co-2-acrylamido-2-methylpropane sulfonic acid)-g-carboxymethylcellulose-Ca (II) (CAA-Ca(II)) hydrogels and FeS-modified CAA-Ca(II) (CAA-Ca(II)-FeS) were synthesized and their adsorption performance toward Pb, Cu, and Cd in unitary, binary, and ternary complex systems were investigated. Experimental results demonstrated that FeS incorporation significantly enhanced the adsorption capacity of CAA-Ca(II), with maximum adsorption capacities reaching 494.30 mg/g for Cd, 374.00 mg/g for Cu, and 783.20 mg/g for Pb in unitary systems. However, under multi-metal coexistence conditions, particularly in the presence of Cu, the adsorption capacities for Cd and Pb were markedly reduced. Quantitative analysis revealed interaction factors below 1.0 for all heavy metal combinations in complex systems, indicating distinct antagonistic effects. The adsorption selectivity followed the order of Cu > Pb > Cd. Mechanistic studies identified that beyond conventional mechanisms including electrostatic attraction, ion exchange, and complexation with amide and sulfonic groups, displacement-precipitation mediated by FeS played a crucial role in the adsorption process. These findings collectively demonstrate that CAA-Ca(II)-FeS serves as a highly promising adsorbent, providing an effective solution for heavy metal removal in complex contamination systems.