Radiation synthesis and chemical modifications of p(AAm-co-AAc) hydrogel for improving their adsorptive removal of metal ions from polluted water

Israa Kamal Abdel Maksoud; Ghada Bassioni; Norhan Nady; Sherif A Younis; Mohamed Mohamady Ghobashy; M S A Abdel-Mottaleb

doi:10.1038/s41598-023-49009-0

Radiation synthesis and chemical modifications of p(AAm-co-AAc) hydrogel for improving their adsorptive removal of metal ions from polluted water

Sci Rep. 2023 Dec 11;13(1):21879. doi: 10.1038/s41598-023-49009-0.

Authors

Israa Kamal Abdel Maksoud¹, Ghada Bassioni², Norhan Nady³, Sherif A Younis⁴, Mohamed Mohamady Ghobashy⁵, M S A Abdel-Mottaleb¹

Affiliations

¹ Department of Chemistry, Faculty of Science, Ain Shams University, Abbassia, Cairo, 11566, Egypt.
² Department of Physics and Engineering Mathematics, Faculty of Engineering, Ain Shams University, Cairo, Egypt.
³ Polymeric Materials Research Department, Advanced Technology and New Materials Research Institute, City of Scientific Research and Technological Applications (SRTA-City), New Borg El-Arab City, Alexandria, 21934, Egypt.
⁴ Analysis and Evaluation Department, Egyptian Petroleum Research Institute (EPRI), Nasr City, Cairo, 11727, Egypt. sherifali_r@yahoo.com.
⁵ Radiation Research of Polymer Department. National Center for Radiation Research and Technology (NCRRT), Egyptian Atomic Energy Authority (EAEA), Cairo, Egypt. Mohamed_ghobashy@yahoo.com.

Abstract

The research focuses on utilizing gamma irradiation to synthesize polyacrylic acid-co-polyacrylamide p(AAm-co-AAc) hydrogels. The effect of synthetic parameters on physicochemical features of p(AAm-co-AAc) hydrogls were examined, including acrylic acid (AAc): acrylamide (AAm) weight ratios, monomer concentration, and gamma irradiation dosage (kGy). At the optimum synthetic conditions (30 kGy and 75% AAc), different chemical modifications are explored to incorporate sulfonate, hydroxyl, carboxyl, cysteine, thiol, and amine functional groups within the bare hydrogel (Cpd 0) structure. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses confirmed the success development of functionalized hydrogels (namely Cpd 1 to 6) with three-dimensional porous structures. These modified hydrogels include Cpd 1, a sulfonated hydrogel through a sulfonation reaction; Cpd 2, modified via NaOH hydrolysis; Cpd 3, modified using thionyl chloride; Cpd 4, incorporating cysteine modification through reaction with cysteine; Cpd 5, with 4-(Dimethylamino) benzaldehyde; and Cpd 6, modified with 3,4-Dimethylbenzoic acid.The effect of hydrogel composition and surface functionalities on the swelling capacity and interactions with scale-forming/heavy metal ions (e.g., Ba²⁺, Sr²⁺, and Cu²⁺) was investigated in saline water solution (NaCl = 1000 mg/L). Batch adsorption studies reveal that all modified hydrogels exhibited higher removal efficiency for the three metal ions than unmodified p(AAm-co-AAc) hydrogel, validating the key role of surface functionalities in tailoring hydrogel affinity for metal ions adsorption. Amongst these, NaOH-treated hydrogel (Cpd 2) outperformed all other modified ones in the removal of Cu²⁺, Ba²⁺, and Sr²⁺ ions, with maximum capacities of 13.67, 36.4, and 27.31 mg/g, respectively. Based on adsorption isotherm and kinetic modeling, the adsorption process of the three metal ions onto all modified hydrogels better obeyed Freundlich isotherm and pseudo-first-order kinetic models. Thermodynamic studies also indicated that the adsorption behavior of Sr²⁺ ions can exhibit both exothermic and endothermic characteristics, depending on the nature of hydrogel surface chemistry. Conversely, the adsorption process of Cu²⁺ and Ba²⁺ ions onto all modified hydrogels is endothermic, suggesting favorable chemical adsorption mechanisms. These findings reveal that the specific adsorption performance of hydrogel is dependent on the type of modification and the targeted heavy metal ions. Based on the nature of hydrogel surface functionality, surface modifications can change the charge density, hydrophilicity, and overall chemical environment of the hydrogel, offering a versatile approach to optimize the adsorption affinity/selectivity of hydrogel's in removing scale-forming/heavy metals from water solutions.