## 3 Effectiveness of Methylated Gamma-Cyclodextrin (M-\(\gamma\)-CD)  
Due to its large cavity depth, \(\gamma\)-CD has a greater capacity for expansion to encapsulate a large number of molecules than other native CDs. Therefore, the chemical modifications of \(\gamma\)-CD through methylation of the hydroxyl group promise to enhance its efficacy in tackling the urgent problem of soil pollution caused by agricultural and industrial processes. Methylated gamma-cyclodextrintrin (M-\(\gamma\)-CD) is a derivative of the \(\gamma\)-CD molecule (see Figure 4). The methylation process enhances the solubility and stability of cyclodextrin while expanding its ability to form inclusion complexes [9]. Methylated \(\gamma\)-cyclodextrintrins (M-\(\gamma\)-CD) demonstrate improved efficacy in extracting specific metal ions from soil matrices. Specifically, cross-linking methylated cyclodext with substances like citric acid or ethylenediaminetetraacetic acid (EDTA) enhances their effectiveness in eliminating toxic metals from polluted soils [18].  
Notably, these derivatives exhibit significant adsorption capacities for Cd (II), with studies reporting removal efficiencies of up to 140.85 mg/g [14]. Additionally, they effectively bind Cu (II) and Pb (II) ions, with capacities varying based on the specific methylation and preparation methods used. M-\(\gamma\)-CD promotes complexation and ion exchange mechanisms, making it suitable for targeting heavy metals such as Hg (II) and Ni (II) as well [19; 24].  
The effectiveness of M-\(\gamma\)-CD in extracting heavy metals is influenced by several factors, including its hydrophilic exterior and hydrophobic interior, hydrogen bonding, pH levels, and the concentration of M-\(\gamma\)-CD [11]. Through non-covalent interactions, this structure allows M-\(\gamma\)-CD to contain organic contaminants and heavy-metal ions within its cavities. Methylation alters cyclodext to be more hydrophobic, which improves their ability to dissolve hydrophobic guest molecules, such as heavy metals [11].  
When heavy-metal ions are encapsulated in the M-\(\gamma\)-CD cavity, the hydroxyl groups form hydrogen bonds with the metal ions. This interaction typically results in the formation of inclusion complexes between M-\(\gamma\)-CD and heavy metals by drastically lowering the transport and availability of lethal elements in biological systems, thereby promoting their effective removal in the environment. The stability provided by hydrogen bonding and van der Waals forces is essential for maintaining the integrity of the complex throughout the adsorption process [18]. A number of researchers have demonstrated that M-\(\gamma\)-CD has remarkable efficacy in extracting various specific heavy metals from contaminated environments, as illustrated in Table 1.  
Figure 4: A methylated schematic diagram of gamma-cyclodextrintrin (M-\(\gamma\)-CD).  
These findings suggest that M-\(\gamma\)-CD serves as an exceptionally effective adsorbent for a variety of heavy metals, thereby positioning it as a promising candidate for applications in environmental remediation. In the context of soil remediation, M-\(\gamma\)-CD (methylated gamma-cyclodextrinntrin) offers several benefits, particularly when treating polluted areas. It significantly enhances the availability and hydrosolubility of pollutants in the soil, making organic pollutants easier to extract and break down, thereby increasing their accessibility for microbial and phytoremediation processes. Compared to traditional remediation methods, which can be costly and complex, M-\(\gamma\)-CD may be a more affordable option. In contrast to multiple synthetic surfactants that can alter the structure and characteristics of soil, M-\(\gamma\)-CD does not form high-viscosity emulsions and exhibits minimal adsorption to soil particles [21; 23; 29].