This study focuses on the removal of lead (Pb), a highly toxic metal ion that poses significant risks to human health and ecosystems. However, current chitosan/acrylic acid-based remediation materials often have limitations in terms of efficiency, stability, and toxicity. In this study, graphene oxide (GO) and carboxylated graphene oxide (GC) were used as modified materials to synthesize two novel hydrogels: polyacrylic acid/chitosan/graphene oxide (PCG) and polyacrylic acid/chitosan/carboxylated graphene oxide (PCC). The adsorbents were characterized using SEM, FTIR, and BET tests. A comprehensive series of adsorption experiments was conducted, optimizing parameters such as pH, temperature, initial Pb(Ⅱ) concentration, and dynamic column. The characteristics of the hydrogels indicate that –COOH and –OH are the primary functional groups; their 3D porous structure, mesoporous structure, and large specific surface area facilitate heavy metal adsorption. Under optimal conditions (pH 5, 25 °C, 0.2 g/L dosage, 500 mg/L initial Pb(Ⅱ) concentration), PCG and PCC achieved maximum Pb(Ⅱ) adsorption capacities of 323.83 and 446.09 mg/g, respectively—demonstrating superior efficiency. PCC demonstrated excellent stability and reusability, retaining an adsorption capacity of 367.44 mg/g after four cycles. It also displayed exceptional acid resistance (adsorption capacity reaches 168.32 mg/g at pH 1.0) and negligible interference (< 5%) from coexisting common ions (K+, Na+, Ca2+, Mg2+). Dynamic column experiments revealed that PCC could effectively treat simulated wastewater containing 50 mg/L Pb(II) for over 900 min while maintaining a 95% removal efficiency. Adsorption kinetic analyses using the PFO and PSO models indicated that chemisorption was the dominant mechanism in the adsorption process. Meanwhile, Langmuir and Freundlich adsorption modeling showed that monolayer adsorption on homogeneous surfaces was the predominant surface adsorption behavior. Boasting relatively low production costs and superior adsorption performance, the hydrogels presented herein offer a promising, effective, economical, and eco-friendly solution for Pb(Ⅱ) remediation in aqueous systems.
Liang et al. (Tue,) studied this question.