## 3 Environmental Applications of Organoclays
### Water Pollution
[66] were combined with a quaternary ammonium modifier by [PERSON] et al. [60]. [PERSON] and [PERSON] [63] and [PERSON] et al. [65] found that modified organolox has a higher pollutant removal capacity than unmodified clay. In 2016, a new trend of grafting clay with polymeric material was observed when [PERSON] et al. [72] and [PERSON] et al. [73] applied organolox for dye removal. Apart from quaternary ammine [69; 70; 71; 75], HNO\({}_{3}\) acid treatment [67], humic acid, N-2-hydroxy-propyl trimethyl ammonium chloride chitosan [74], and zwetter-ionic surfactant, such as 1,10-didodecyl-4,40-trimethylene bispyridinium bromide and 1,10-dihexadecyl-4,40-trimethylene bispyridinium bromide [68], were applied for dye removal, phenol removal, and heavy metal removal. [PERSON] et al. [76] studied the effect of different alkyl chain head groups on the removal of 2,4,6-trichlorophenol and found that a higher number of head groups has a higher removal capacity due to packing density and ion-dipole interactions. [PERSON] et al. [78], and [PERSON] et al. [80] addressed phenol removal by using a quaternary ammonium modifier. [PERSON] [77] addressed the removal of heavy metals by modified chitosan-based clay. Similarly, [PERSON] et al. [79] studied the effect of quaternary ammonium modifier and chitosan hybrid on removing phenol, Pb\({}^{2+}\) heavy metals and removing conger red and crystal violet dyes and found that hydrophobic integration is the main factor for adsorption. Figure 4 shows the role of the binding sites in the adsorption of pollutants. In 2018, our publication [81] provided a detailed mechanism for phenol and nitrobenzene adsorption. In addition, the role of hydrophilic materials like phenol in adsorption and the role of hydrophobic materials like nitrobenzene in adsorption were studied with their behaviors. Long-chain modifiers have been found to have the affinity to increase d-spacing and provide more sites for adsorption. In Figure 4, it can be seen that phenol is at adsorption Site 1, i.e., the outer layer of clay, while Site 2 is for the intermediate layer and Site 3 for molecules. This was the phenomenon in which Langmuir monolayer adsorption was studied layer by layer. In the same year, the removal of heavy metals, phenols, fluorides, and dyes was studied by [PERSON] [82], [PERSON] et al. [83], [PERSON] et al. [84], [PERSON] et al. [85], and [PERSON] et al. [86]. In 2019, [PERSON] et al. [89] used magnetic nanoparticles along with surfactant for the modification of montmorillonite for the removal of methylene blue dye. In this year, [PERSON] et al. [87] and [PERSON] et al. [88] used the cation-exchange method for the removal of dye. Meanwhile, [PERSON] et al. [90], [PERSON] et al. [91], and [PERSON] et al. [92] had used Fe(NO\({}_{3}\))\({}_{3}\).9H\({}_{2}\)O, chitosan, and L-lysine for heavy metal removal. Meanwhile, in the same year, [PERSON] et al. [93] and [PERSON] [94] used gemini surfactant and the silane modifier modification of montmorillonite clay for ester removal and phenol removal, respectively. The removal of perfluoro-octanoic acid by hexadecyltrimethyl ammonium (HDTMA) and poly-4-vinylpyridine-co-styrene (PVPcos)-modified Na montmorillonite was reported by [PERSON] et al. [95]. In 2020, [PERSON] and [PERSON] [96] and [PERSON] et al. [97] modified montmorillonite with hexadecyltrimethylammonium and octadecylamine for phenol removal. Meanwhile, [PERSON] et al. [98] studied montmorillonite and biochar composite for heavy metal removal. [PERSON] et al. [99] used Cetlypyridinium chloride as a modifier for heavy metal removal. At the same time, [PERSON] et al. [100] used starch and montmorillonite clay for Pb and Cd removal. Meanwhile, [PERSON] and [PERSON] [101] used chlorosulfonic acid as a modifier to degrade trihalo methane. Dye removals through montmorillonite composite were performed in the same year by [PERSON] et al. [102], [PERSON] et al. [103], and [PERSON] and [PERSON] [104]. In 2021, [PERSON] and [PERSON] [105] used cetyltrimethylammonium bromide for dye removal.