Uranium Removal from Water Samples by a New Adsorbent Based on Amino Acid Grafted Biopolymer/Polyacrylic Acid Using a High Energy Irradiation Method

Abstract

A biocompatible hybrid hydrogel adsorbent was prepared by chemically grafting aspartic acid (AA) with pectin (Pc) and hybridizing it with polyacrylic acid (PAAc) using a high-energy electron irradiation method. The chemical structure of the hybrid hydrogel was evaluated through Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analysis, Thermal Gravimetric Analysis (TGA) and X-ray Diffraction (XRD). The ability of hydrogel to remove uranium from aqueous samples was investigated. The parameters affecting the uranium removal process were optimized. After optimizing the parameters, the best irradiation dose for hydrogel production was 20 kGy and the best uranium adsorption conditions were pH = 7 and contact time 2 h. The adsorption capacity of the hybrid hydrogel was improved from 236.5 to 386.3 mg/g after modifying pectin with aspartic acid. The adsorption data were analyzed by different models, and the experimental results were in better agreement with the Langmuir isotherm. Uranium adsorption kinetics followed second-order pseudo model more closely. According to thermodynamic data, the uranium adsorption process by the proposed sorbent was endothermic and spontaneous. The performance of the hybrid hydrogel did not change significantly after 4 adsorption/desorption cycles. The results of this work introduced a new efficient adsorbent with biocompatibility and biodegradability properties for the practical applications of removing uranium from aqueous wastes.