Iron nanoparticles embedded porous chitosan for antimony removal: exceptional adsorption capacity, cations resistance and environmental recyclability

Antimony (Sb) is an important element applied in many industries, and its uncontrolled discharge into the environment has seriously impacted the ecological systems. Bulk adsorbents such as metal oxides, metal nanoparticles, metal salts, and organic-metal frameworks were used with a low atom utility efficiency for Sb recovery. In this work, zero-valent iron nanoparticles (Fe(0)) were uniformly embedded on bio-derived porous chitosan hydrogel via an in-situ reduction procedure. The as-prepared materials improve Sb adsorption uptake up to 175.89 mgSb·g−1Ad or 2240.73 mgSb·g−1Fe, far more than those of the previously reported bulk iron analogs, highlighting the significant role of supporting strategy in enhancing Fe-atom efficiency. The variations of the performances with the experimental parameters, including contacting time, initial Sb amount, adsorbent doping, temperature, coexisting cations, pH, as well as cyclic removal performance, were fully investigated. The materials exhibit a robust resistance to high concentrations of interfering cations Co2+, Ni2+, Cu2+, As3+, Sr+, and Cd2+ with a significant adsorption constant ratio KSb/M up to 214–4548. The resilience to performance fatigue is highlighted by five consecutive adsorption–desorption cycles retaining over 80.9 % of the original efficiency, supporting circular economy. The adsorption pathway, including oxidation–reduction and ionic affinity, has been probed, and XPS corroborates the findings. The developed fabrication strategy shows fundamental guidance for constructing highly efficient eco-friendly materials for treating Sb-polluted water and can be extended to other hazardous substances.