## 3 Results and Discussion
### Characteristics of the Amine Immobilized GMA-g-NWF and IRP
#### 3.2.3 Water Absorptive Capacity Analysis  
An adsorbent with good water uptake capacity is one of the important criteria as maximum delivery of water plays a crucial role in both adsorption and desorption processes in terms of energy efficacy [33]. Hence, the water uptake capacity of both amine immobilized GMA-\(g\)-NWF, and IRP samples were tested. The results obtained illustrated in Figure 4. Good cycling performance of an adsorbent is highly dependent on material's water stability properties as well. Water uptake capacity of amine immobilized GMA-\(g\)-NWF increases as the aliphatic amine chains grow longer. The maximum water uptake capacity recorded for EDA-GMA-\(g\)-NWF, DETA-GMA-\(g\)-NWF, TETA-GMA-\(g\)-NWF, and TEPA-GMA-\(g\)-NWF samples were around 360%, 466%, 400% and 733%, respectively. A similar trend was attained for IRP samples. The maximum water uptake capacity recorded for EDA-IRP, DETA-IRP, TETA-IRP, and TEPA-IRP samples were around 733%, 933%, 1066% and 1300%, respectively. However, it is very noticeable that IRP samples exhibited higher water uptake capacity in comparison to amine immobilized GMA-\(g\)-NWF samples. One of the possibilities behind this is due to the morphology of the polymer that strongly affects the water uptake kinetics. For IRP samples, the imprinting effect generated an organized structure and enabled water to transport through the voids from the cavity. Figure 3: FTIR spectra of (**a**) EDA-GMA-\(g\)-NWF and EDA-IRP, (**b**) DETA-GMA-\(g\)-NWF and DETA-IRP, (**c**) TETA-GMA-\(g\)-NWF and TETA-IRP, (**d**) TEPA-GMA-\(g\)-NWF and TEPA-IRP at experimental condition of 70% amine: 30% isopropanol, 60 \({}^{\circ}\)C, Dg \(\sim\)100% and 2 h.  
The adsorption capacity of both type samples was investigated. The result obtained for Cu adsorption is shown in Figure 6. The complete experimental data for adsorption capacity of both Cu and Pb is provided in the Supplementary Materials. The experimental conditions of the amine functionalization process were predetermined to attain AD approximately 2.0-2.2 mmol/g\({}^{-\text{ad}}\) provided standardized condition was applied for adsorption experiment. The adsorption capacity of Cu for both amines immobilized GMA-\(g\)-NWF, and IRP samples were measured against adsorption time. The adsorption capacity of EDA-GMA-\(g\)-NWF towards Cu ion increases significantly for the initial 60 min, but after that, the adsorption capacity reaches almost plateau. The adsorption capacity EDA-GMA-\(g\)-NWF at first 15 min of adsorption was around 1.60 mg/g which increases up to 34.85 mg/g after 60 min of the process. The active sites present onto EDA-GMA-\(g\)-NWF more likely actively occupied during the initial stage of the adsorption process. However, subsequent saturation in adsorption of Cu ion merely takes place due to the exhaustion of active sites onto EDA-GMA-\(g\)-NWF [35]. The saturation is resulted from the simultaneous adsorption of Pb, suggesting possible competitive effect towards the active sites between Cu and Pb. A similar trend was attained for DETA-GMA-\(g\)-NWF, TETA-GMA-\(g\)-NWF, and TEPA-GMA-\(g\)-NWF samples as well. The adsorption capacity of amine immobilized GMA-\(g\)-NWF samples decreases as the aliphatic amines chain grows greater. The adsorption capacity towards Cu ion reduces with a trend of EDA-GMA-\(g\)-NWF \(<\) DETA-GMA-\(g\)-NWF\(<\) TETA-GMA-\(g\)-NWF. These findings strongly related to the size of aliphatic amines. Since the EDA possesses the smallest size, thus the migration of EDA onto epoxy groups of GMA takes place in abundant in comparison to other aliphatic amines [4]. Another main reason for the reduction of adsorption capacity towards Cu ion as the number of amines increased from 2 to 5 is related to the covalent interactions relative to the ionic interactions during the competitive adsorption between Cu and Pb. [PERSON] et al.