Eco-friendly and cost-effective superabsorbent sodium polyacrylate composites for environmental remediation

In this research, we synthesized superabsorbent polymers (SAPs) based on poly(acrylic acid) with super adsorption properties through a novel one-step cost-effective method. The SAPs’ adsorption for removal of heavy metal ions [e.g., Cu(II)] from aqueous solutions was systematically studied. The effects of pH (2.0–5.0), sodium hydroxide and water composition, contact time (0–48 h), and initial Cu(II) ion concentrations (1–500 mg dm−3) on the adsorption of Cu(II) ions were studied using atomic absorption spectroscopy. The adsorption behavior was fitted to a Langmuir isotherm and shown to follow a pseudo-second-order reaction model. The maximum adsorption capacities of Cu(II) ions were shown to be 243.91 mg g−1 for sodium polyacrylate (PAANa), which is among the highest adsorption capacities reported in the literature. The superior adsorption capacity of Cu(II) ions is attributed to the chelating ability of functional groups (e.g., –COO−) in the PAANa matrix. The recyclability of the PAANa material showed that over 98.92 % of the adsorbed copper could be recovered in a mild concentration (0.01 M) of nitric acid. Results of three consecutive adsorption–desorption cycles showed that the composites had high adsorption and desorption efficiency, implying that PAANa samples can be recycled and reused as an effective adsorbent for Cu(II) recovery.