## 2 Clays and Organoclays
### Preparation  
There are several methods of making organoclay that can be used to modify a given clay to create a larger surface area for each particle in the clay. This first and most common method of producing organoclay is ion-exchange modification (cation/anion exchange) [19]. The ion-exchange method is used to improve the clay's ability to hold positively/negatively charged ions, such as heavy metal ions and phenols that are regularly found in wastewater. To prepare the clay by cation exchange, the clay must be dissolved and mixed with an \begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt}} \hline \hline
1. Quaternary ammonium salts (QAS) & 5. Others \\ Quaternary phosphonium cations & Silane materials (3-aminopropyl)-triethoxysilane \\ Octadecylammonium ions & Alkyloxymethyl dimethyl dodecylammonium chlorides \\ Dodecyltrimethylammonium bromide & Bis(2-hydroxyethyl)lahurylammonium \\ Tetradecyl trimethyl ammonium bromide & Diethyl [2(methoxyyloxyl)]ethylammonium(DEM-M), \\ Hexadecyl trimethyl ammonium bromide & Quinoline and pyridine groups \\ Tetradecyldimethylbenzyl1 ammonium bromide & 2-methylacryloxymethyl dimethyl hexadecylammonium bromide \\ Hexadecylldimethylbenzyl1 ammonium bromide & Linear alcohol ethoxylate \\ Octadecylldimethylbenzyl1 ammonium bromide & p-phenylamino-azo-benzene sodium sulfonate \\ Tetra n-octylammonium bromide & p-amino diphenylamine \\ Dimethylidioctylammonium bromide & Benzidine crown-ethers \\ Dimethyldisteeralleammonium bromide & Cryptand imadazolium salts \\
2. Polymeric quaternary ammonium salts & 2-aminopyrimidine \\ p-xylylenedichlorides and diamines & Alkylphosphonium cations of (4-carboxybutyl)-Triphenylphosphonium bromide \\ p-xylenedichlorides and diamines & Methylene blue cations \\ tetramethyl-ionenes, & \(\gamma\)-metacryloxymethyl dimethyl methoxysilane \\ Epichloridin-dimethylamine & Trifunctionaly-methacryloxymethyl trimethoxysilane \\ Triethylamine, vinylbenzyl chloride, and lauryl acrylate copolymer & Coupling agents \\ Styrene, lauryl acrylate, and vinylbenzyl chloride & \(\gamma\)-aminopropyl trimethoxysilane \\
4-acetylphenil Polyethylene-blockpoly(ethylene glycol) copolymers & Aniline salts AnCl, AnBr and AnI \\ poly(ethylene glycol) & Aluminum hydroxide \\ Maleic anhydride and pentaerythnitol & Aminopropyl and propyl trimethylammonium histidine \\ Polyethersulfone membrane & histidine \\ Poly(amido amine) (PAMAM) dendrimers & 3-(N,N-di-methylhexadecylammoniumio) propane sulfonate \\
3. Ammonium salts & 1,3-bis(hexadecyldimethylylammoniumio)- propane dibromide \\
1-hexadecylamine, & 1-octadecylamine, & bis-pyridinium dibromide \\
4. Common gemini surfactants & 3-(N,N-di-methylhexadecylammoniumio) propane sulfonate \\ pyridyl-containing gemini surfactants & 1,3-bis(hexadecyldimethylammoniumio)- propane dibromide \\ Aromatic- containing gemini surfactants & dibromide \\ Imidazoline- containing gemini surfactants hydroxyl- & 1,3-bis(dodecyldimethylammoniumio)- propane dibromide \\ Containing gemini surfactants & 1,3-bis(hexadecyldimethylammoniumio)-2-hydroxypropane \\ Imino- containing gemini surfactants & dichloride \\ Ether- containing genini surfactants & 1,3-bis(octyldimethylammoniumio)-2-hydroxypropane dichloride \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of the commonly used organic modifiers used to synthesize organoclays. amount of modifier equal to the CEC of the clay. The second modification method is the solid-state reaction method [21], in which two solid starting materials, the clay and the modifier, react directly with each other. A solid-state reaction is environmentally friendly because it does not require solvents in its manufacture and makes the process more amenable to large-scale industrialization. Since solids do not react with each other at room temperature, it is necessary to heat them to extreme temperatures ranging from around 1000 to 1500 \({}^{\circ}\)C. In this process, a volatile liquid, such as alcohol or acetone, is added to create a paste that eventually evaporates back into a solid.