## 3 Environmental Applications of Organoclays
### Air Pollution
[140] demonstrated the adsorption of CO\({}_{2}\) on bio-based chitosan-polybenzokazine-modified clay-based nanocomposite and amine-impregnated porous montmorillonite nanoclay, respectively. The modified chitosan-based composite had a CO\({}_{2}\) adsorption of 5.72 mmol/g at ambient conditions. In the study by [PERSON] et al. [140], they found that unmodified montmorillonite adsorbed 3.34 mmol/g CO\({}_{2}\) at room temperature and a bar pressure of 50 while modified clay under the same conditions adsorbed 3.47 mmol/g of CO\({}_{2}\). [PERSON] et al. [141] modified bentonite and montmorillonite clay with perhydroxylated glucodendrimer for CO\({}_{2}\) adsorption and CRC data revealed that CO\({}_{2}\) adsorption involves physical adsorption with the OH of the dendrimer. In the same year, [PERSON] et al. [27] conducted a study of the adsorption of CO\({}_{2}\) and NH\({}_{3}\) gas regarding cationic clay and anionic clay. The phenomenon obtained is shown in Figure 5. It can be seen that the NH2-terminated dendrimer has an affinity for adsorbed CO\({}_{2}\) and the COO-terminated group has an affinity for NH\({}_{3}\) adsorption. Furthermore, desorption experiments showed that the adsorbed CO\({}_{2}\) is desorbed from the clay and is retained on the dendrimer since dendrimers have the affinity to keep the gas at room temperature due to their nanopores. [PERSON] et al. [142] investigated amino-acid-modified montmorillonite clay as a suitable material for CO\({}_{2}\) adsorption and separation from other gases in large-scale processes. They found the adsorption value of CO\({}_{2}\) to be 0.8 mmol/g at a temperature of 25 \({}^{\circ}\)C and a pressure of 8 bar. In addition, they achieved a selectivity values of 170 in CO\({}_{2}\)/CH\({}_{4}\) separation under a bar pressure of 9. In 2019, [PERSON] et al. [143] reported reversible CO\({}_{2}\) capture with acid-activated bentonite achieved by the chemical grafting of 3-aminopropyltriethodysilane or 3-diethanolamiopropyltriethodysilane. They found that acid treatment increases the number of silanol groups and silylation capacity but compromises CRC capacity. This decay was revived by refining clay with a modifier. In the same year, [PERSON] et al. [144] modified montmorillonite, bentonite, saponite, sepiolite, and palgorskite clays via three methods: (1) grafting with aminopropyl and diethylenetriamine organosilanes; (2) impregnation with polyethylenimine; and (3) dual functionalization by the impregnation of previously grafted for \(\mathrm{CO_{2}}\) adsorption. They found that the CO\({}_{2}\) uptake of a grafted and impregnated sample ranged from 61.3 to 67.1 mg/g. [PERSON] et al. [145] performed acid activation on montmorillonite for \(\mathrm{CO_{2}}\) adsorption. They found that three hours of acid activation increased the surface area of the clay from 39 to 202 m\({}^{2}\)/g while the pore volume increased from 0.05 to 0.31 cm\({}^{3}\)/g, showing higher CO\({}_{2}\) adsorption capacity. In 2021, [PERSON] et al. [147] used nano-montmorillonite impregnated with diethanolamine for \(\mathrm{CO_{2}}\) adsorption and found that it had a \(\mathrm{CO_{2}}\) adsorption of 219.9 mg/g. At the same time, [PERSON] and [PERSON] [146] modified montmorillonite clay with strontium hydroxide for \(\mathrm{CO_{2}}\) adsorption and found that it had a \(\mathrm{CO_{2}}\) adsorption of 102.21 mg/g at 25 \({}^{\circ}\)C and a bar pressure of 9. [PERSON] et al. [148] synthesized organo-montmorillonite by a simple dry ball-milling method with tetramethylammonium bromide as a modifier. This modified vessel was used to adsorb gaseous toluene. The dynamic adsorption of modified clay was found to result in 55.9 mg/g of toluene adsorption compared to 8.8 mg/g of toluene with unmodified clay. In the next year, [PERSON] et al. [151] synthesized tetramethylammonium bromide-modified clay by ball milling for the application of gaseous acetone adsorption. [PERSON] et al.