## 3 Results and Discussion
### Adsorption of Magnetic Nanomaterials  
#### 3.2.1 Effect of Contact Time  
The extent of adsorption was mainly dependent on the contact time between the adsorbent and the chemical agents. Therefore, experiments were conducted with an optimized contact time ranging from 0 to 20 min. The adsorption rate curves depicted in Figure 10 indicated that both L and VX consistently maintained a high adsorption rate, with minimal change observed over the course of the adsorption time. This could be attributed to the adsorption behavior being classified as physisorption or physical adsorption. In physisorption, high adsorption rates were achieved through dispersion forces between molecules. Additionally, L was a relatively large molecule with low vapor pressure, and VX was also characterized by its large organic structure and high molar mass. These factors contributed to the ease of physisorption for both L and VX [5]. Physisorption was governed by forces such as long-range London dispersion forces and short-range intermolecular repulsion, which give rise to nonspecific molecular interactions [40]. Furthermore, the MGONCs obtained a high surface area and a mesoporous structure, suggesting that L and VX could easily attach to the surface of the adsorbent during the adsorption process.  
In Figure 10, it could be observed that the adsorption rate of GB and GD increased with the increase in adsorption time, but no significant increase was observed beyond 300 s. The initial increase in the adsorption rate with time could be attributed to the greater contact time between the adsorbent and the adsorbate. During the first 300 s, the concentration difference between the bulk solution and the solid-liquid interface led to a rapid adsorption rate. However, after 300 s, the adsorption speed slowed down, likely due to the slower diffusion rate of GB and GD into the interior channels of MGONCs once the surface sites of the adsorbent became saturated with adsorbed targets [41]. To ensure consistent adsorption rates for various chemical agents, an optimized adsorption time of 20 min was established for subsequent studies.  
In addition, MGONCs could achieve a complete adsorption of L and VX within 1 min, and near-complete adsorption of GB and GD under 20 min. [PERSON] et al. prepared molecularly imprinted polymers and studied their adsorption of GB, GD, tabun, and VX. It was found that the adsorption tended to be saturated within 16 h. After the 72 h of adsorption, the adsorption rate of VX only reached 25% [42]. [PERSON] et al. prepared zirconium hydroxide over woven activated carbon fabric for the adsorption and degradation of chemical warfare agents, which could reach 85% under the condition of 20 min [43]. Compared with the reported research, the MGONCs prepared in our research revealed a better rapid adsorption, which was particularly important for the removal of chemical agents.  
Figure 9: N\({}_{2}\)-adsorption/desorption isotherm of MGONCs.  
Figure 11: Adsorption rate of MGONCs of different adsorbent dosages: (**a**) for L; (**b**) for VX; (**c**) for GB; (**d**) for GD.  
Figure 12: Adsorption rate of MGONCs at different adsorption temperatures: (**a**) for L; (**b**) for VX; (**c**) for GB; (**d**) for GD.  
Considering the adsorption curve after adjusting the adsorbent dosage in Section 3.2.2, little influence on the adsorption of L, VX, and GB was observed as the adsorption sites have already reached saturation at 10 mg. However, the temperature had a significant effect on the adsorption rate of GD. The higher temperature led to an increased swelling of the adsorbent, resulting in more active sites being available [45]. The diffusion of GD occurred both externally and internally within the adsorbent. The increasing adsorption capacity with temperature indicated that the adsorption process was identified as an endothermic reaction [44].