## 3 Environmental Applications of Organoclays
### Air Pollution  
The adsorption of CO\({}_{2}\) on amide-based surfaces has been very famous and, hence, the modification of clay or the grafting of clay by amide modifiers for the adsorption of gas pollutants has been the main focus of the last 10 years of research. Several studies have been published on the use of clay materials as an adsorption material for air pollutants, such as CO\({}_{2}\), H\({}_{2}\), NH\({}_{3}\), VOC, etc. Table 4 summarizes the list of modifiers and their applications that are specific to gas adsorption. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Clay** & **Modifier** & **Methodology** & **Application** & **Efficiency** & **Reference** \\ \hline \multirow{6}{*}{\
\begin{tabular}{c} Na- \\ Montmorillonite \\ (Boltorn) \\ \end{tabular} } & Ethylene glycol & & & & \\  & Trizmabase & & & & \\  & Penterythnitol & & & & \\  & Mannitol & & & & \\  & Dipentaerythnitol & & & & \\  & Ethoxylated pentaerythnitol & & & & \\  & (D)-(+) Trehalose & & & & \\  & Polyvinyl alcohol & & & & \\ \hline Bentonite (Aldrich) & Sodium chloride & & & & \\  & & & & & \\  & & & & & \\ \hline Bentonite (Aldrich) & Sodium chloride & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\ \hline Cloisite (Southern Clay Products) & 3-aminopropyltrimethoxysilane & & & & \\  & Polyethylenimine & & & & \\ \hline Bentonite (Sudan) & Ammonium cations & Cation exchange & CO\({}_{2}\) Removal & 3.15 mmol g\({}^{-1}\) & [135] \\ \hline Montmorillonite & & & & & \\  & Diamine & & & & \\  & & & & \\  & & & & & \\ \hline Na- & (3 aminopropyl)triethoxysilane & & & & \\  & Ethylene glycol & & & & \\  & & & & \\  & & & & \\  & & & & \\ \hline Laponite & poly(amido amine) dendrimers & & & & \\  & Hydotalcite & G4.0 and poly(amido amine) & Cation exchange & & \\  & Sericite & dendrimers G4.5 & & & \\ \hline Chitosan (Aldrich) & Na-MMT & Carbon aerogel & CO\({}_{2}\) Removal & 5.72 mmol g\({}^{-1}\) & [139] \\ \hline Montmorillonite & & & & & \\  & Amine grafting & & & & \\  & & & & \\ \hline Bentonite (Aldrich) & Perhydroxylated glucodendrimer &
\begin{tabular}{c} Thermal \\ desorption \\ Impregnation \\ \end{tabular} & CO\({}_{2}\) Removal & 1.5 mmol g\({}^{-1}\) & [141] \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary of the application of natural clay and its modified clay in the removal of air pollutants and its efficiency. [PERSON] et al. [131] used Boltorn polyol dendrimers to modify montmorillonite to enhance the hydrophilic nature of montmorillonite for CO\({}_{2}\) adsorption under dry and wet conditions. They found that the OH of clay has slightly less adsorption than OH-H\({}_{2}\)O. They also found that the dry-state desorption of CO\({}_{2}\) gas is very easy and can be performed at 20-50 \({}^{\circ}\)C while wet-state gas desorption requires a higher temperature range, such as 60-70 \({}^{\circ}\)C, for desorption. The result obtained confirms the role of physical adsorption and the nature of physico-chemical interactions in wet conditions. [PERSON] et al., [132] used three polyglycerol dendrimers with different molecular weights, like 500, 1100, and 1700, from soybean oil and modified Na montmorillonite clay to perform reversible CO\({}_{2}\) capture. The CO\({}_{2}\) retention capacity (CRC) was measured by temperature program desorption and revealed that the CO\({}_{2}\) retention increased with the increasing OH group. They found that higher generation and higher loading of the clay surface with dendrimers markedly reduced the accessible sites for OH groups and