# Nanofiber-Based Materials for Persistent Organic Pollutants in Water Remediation by Adsorption
## 4 Persistent Organic Pollutants
### Aliphatic Organochlorines  
#### 4.1.1 Adsorbate Properties  
Table 10 shows the physico-chemical characteristics of selected aliphatic organochlorines in this review, namely Aldrin, Dieldrin, Endrin, Chlordane, Heptachlor, Heptachlor eposide, and Toxaphene 8. Drin pesticides possess an alicyclic structure with 6 chlorine groups. The Aldrin molecule is formed by reaction of norbornadiene, a bicyclic hydrocarbon, and hexachlorocyclopentadiene, also called C-56. In specific conditions, such as in living organisms, Aldrin can be oxidised to form Dieldrin. Endrin is a stereoisomer of Dieldrin, differing in the spatial orientation of the oxygen group, as well as one hydrogen and one chlorine bond. Cyclodiene compounds selected in this study also comprise Chlordane and Heptachlor. Also derived from hexachlorocyclopentadiene, Chlordane and Heptachlor have eight and seven chlorine atoms, respectively, surrounding the polycyclic organic structure. It has been observed that when Heptachlor penetrates the soil, it can be turned into Heptachlor epoxide by soil microorganisms in an epoxy reaction. Toxaphene is another polycyclic organochlorine compound, formed by the chlorination of camphene, usually by chlorine gas. Also called camphechlor or polychlorocomaphene, Toxaphene 8 possesses eight chlorine groups [26].  
Except for Toxaphene, all molecules present one unsaturated bond, enabling adsorption via \(\pi\)-\(\pi\) stacking of electrons with suitable adsorbents. Dieldrin and Endrin present three chlorine groups at proximity, while other molecules show two chlorine groups, except for Aldrin, which does not show any hydrophobic group near the unsaturated bond.  
Selected organochlorine POPs are of a similar weight, ranging from 365 g/mol for Aldrin to 414 g/mol for Toxaphene; however, they differ in their spatial orientation. Apolar molecules have a solubility in water below 0.6 mg/L, with octanol-water partition coefficients over 5. Dieldrin, Endrin and Heptachlor epoxide are only slightly polar molecules due to the presence of one oxygen group (an electron acceptor group), which significantly improves their water affinity (0.019 mg/L for Aldrin and 0.19 mg/L for Dieldrin) and is believed to improve binding with adsorbents by electrostatic interaction.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Name**} & \multicolumn{2}{c}{**Molecular**} & \multirow{2}{*}{**Log K\({}_{\text{env}}\)**} & \multicolumn{2}{c}{**Solubility in Water**} & \multirow{2}{*}{**2D Structure**} & \multicolumn{2}{c}{**H Bound Count**} \\ \cline{2-2} \cline{5-6}  & **Weight (g/mol)** & & & & **Formula** & & **Donov** & **Acceptor** \\ \hline \multirow{2}{*}{Aldrin} & \multirow{2}{*}{364.896} & \multirow{2}{*}{C\({}_{2}\)H\({}_{6}\)Cl\({}_{6}\)} & \multirow{2}{*}{5.6} & \multirow{2}{*}{0.027} & \multirow{2}{*}{0} & \multirow{2}{*}{0} & \multirow{2}{*}{1} \\ \cline{1-1} \cline{6-6}  & & & & & & & \\ \hline \multirow{2}{*}{Dieldrin} & \multirow{2}{*}{380.895} & \multirow{2}{*}{C\({}_{2}\)H\({}_{6}\)Cl\({}_{6}\)} & \multirow{2}{*}{5.4} & \multirow{2}{*}{0.19} & \multirow{2}{*}{*}{\(<\)\