This review discusses the roles of anion exchange membrane (AEM) as a solid-state electrolyte in fuel cell and electrolyzer applications. It highlights the advancement of existing fabrication methods and emphasizes the importance of radiation grafting methods in improving the properties of AEM. The development of AEM has been focused on the improvement of its physicochemical properties, including ionic conductivity, ion exchange capacity, water uptake, swelling ratio, etc., and its thermo-mechano-chemical stability in high-pH and high-temperature conditions. Generally, the AEM radiation grafting processes are considered green synthesis because they are usually performed at room temperature and practically eliminated the use of catalysts and toxic solvents, yet the final products are homogeneous and high quality. The radiation grafting technique is capable of modifying the hydrophilic and hydrophobic domains to control the ionic properties of membrane as well as its water uptake and swelling ratio without scarifying its mechanical properties. Researchers also showed that the chemical stability of AEMs can be improved by grafting spacers onto base polymers. The effects of irradiation dose and dose rate on the performance of AEM were discussed. The long-term stability of membrane in alkaline solutions remains the main challenge to commercial use.

This paper investigates the selectivity of GMA-based-non-woven fabrics adsorbent towards copper ion (Cu) functionalized with several aliphatic amines. The aliphatic amines used in this study were ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA). The non-woven polyethylene/polypropylene fabrics (NWF) were grafted with glycidyl methacrylate (GMA) via pre-radiation grafting technique, followed by chemical functionalization with the aliphatic amine. To prepare the ion recognition polymer (IRP), the functionalized amine GMA-grafted-NWF sample was subjected to radiation crosslinking process along with the crosslinking agent, divinylbenzene (DVB), in the presence of Cu ion as a template in the matrix of the adsorbent. Functionalization with different aliphatic amine was carried out at different amine concentrations, grafting yield, reaction temperature, and reaction time to study the effect of different aliphatic amine onto amine density yield. At a concentration of 50% of amine and 50% of isopropanol, EDA, DETA, TETA, and TEPA had attained amine density around 5.12, 4.06, 3.04, and 2.56 mmol/g-ad, respectively. The amine density yield decreases further as the aliphatic amine chain grows longer. The experimental condition for amine functionalization process was fixed at 70% amine, 30% isopropanol, 60 °C for grafting temperature, and 2 h of grafting time for attaining 100% of grafting yield (Dg). The prepared adsorbents were characterized comprehensively in terms of structural and morphology with multiple analytical tools. An adsorptive removal and selectivity of Cu ion by the prepared adsorbent was investigated in a binary metal ion system. The IRP samples with a functional precursor of EDA, the smallest aliphatic amine had given the higher adsorption capacity and selectivity towards Cu ion. The selectivity of IRP samples reduces as the aliphatic amine chain grows longer, EDA to TEPA. However, IRP samples still exhibited remarkably higher selectivity in comparison to the amine immobilized GMA-g-NWF at similar adsorption experimental conditions. This observation indicates that IRP samples possess higher selectivity after incorporation of the ion recognition imprint technique via the radiation crosslinking process.

A low cost adsorbent, banana stem fibers (BSFs), was used for modification by grafting with methacrylic acid via three free radical generation methods. The presence of poly(methacrylic acid) on the adsorbent surface was verified by FTIR, ESR and TG analyses. BSFs grafted via β-radiation (BSF-β) were proven to have a higher grafting yield which led to a higher Hg(II) adsorption capacity. A slight decrease in the equilibrium pH after the adsorption process was probably due to BSF-β acting as an acid-form ion-exchanger. The adsorption equilibrium uptake fitted well with the Freundlich isotherm model implying that Hg(II) adsorption occurred heterogeneously on the adsorption sites. The kinetics of adsorption follows a pseudo-first order model with an activation energy of 13.7 kJ mol⁻¹ indicating that the adsorption undergoes an ion-exchange process. Thermodynamic studies illustrated that that the Hg(II) adsorption process was endothermic and non-spontaneous. Spent BSF-β was effectively regenerated with 0.1 M HCl and could be reused without any significance efficiency loss over at least six cycles of adsorption. The present investigation shows that BSF-β is a promising adsorbent for the removal and recovery of Hg(II) ions from aqueous solutions.

Phosphorylated adsorbent is commonly used in the extraction of rare earth metals and radioactive waste because of its high affinity in acidic condition. In this study, adsorbent containing phosphoric acid groups was synthesized by one-step radiation-induced grafting of 2-hydroxyl methacrylate phosphoric acid monomer (2-HMPA) onto kenaf fibers. The kenaf fibers were pre-treated with sodium chlorite prior grafting process. The incorporation of poly (2-HMPA) in the bleached kenaf fibers was confirmed by Fourier transform infrared spectroscopy (FTIR), FT-IR chemical imaging and scanning electron microscopy (SEM). The structural property was investigated using X-ray diffraction (XRD). The result revealed optimum grafting yield of 91.3% with 10% 2-HMPA and 50 kGy at 40 °C for 3 h. The performance of the synthesized adsorbent showed almost complete thorium adsorption. The removal efficiency of 99.9% thorium from aqueous solution was achieved using fibrous adsorbent at an initial thorium concentration of 10 mg/L, a reaction time of 3 h, and pH of 3 at room temperature. This single step combining grafting and functionalization to modify kenaf fibers showed sufficient property for application of natural fibers as adsorbent.