# Nanofiber-Based Materials for Persistent Organic Pollutants in Water Remediation by Adsorption
## 2 Moderately Hydrophobic Pesticides
### Nanofibers for Pesticide Adsorption  
#### 2.2.1 Impact of Adsorbent Specific and Contact Surface Area  
Figure 1 shows the impact of the adsorbent specific surface area (BET) on the adsorption removal. The removal percentage was overall found to decrease with increasing adsorbent specific surface area for both Alachlor and Diazinon, yet was found to increase in the case of Atrazine removal. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Name**} & \multicolumn{2}{c}{**Molecular**} & \multirow{2}{*}{**Log K\({}_{\text{aw}}\)**} & \multirow{2}{*}{**Solubility in Water** (mg/L, 25 °C) & \multirow{2}{*}{**2D Structure**} & \multirow{2}{*}{**H Bound Count**} \\ \cline{2-2} \cline{6-6}  &
\begin{tabular}{c} **Weight** \\ **(g/mol)** \\ \end{tabular} & & & & & **Donor** & **Acceptor** \\ \hline \multirow{2}{*}{**Alachlor**} & \multirow{2}{*}{269.769} & \multirow{2}{*}{C\({}_{14}\)H\({}_{20}\)CINO\({}_{2}\)} & \multirow{2}{*}{3.52} & \multirow{2}{*}{240} & \multirow{2}{*}{**Donor**} & \multirow{2}{*}{**Acceptor**} \\ \cline{1-1} \cline{6-6}  & & & & & & \\ \hline \multirow{2}{*}{**Atrazine**} & \multirow{2}{*}{215.665} & \multirow{2}{*}{C\({}_{6}\)H\({}_{14}\)CIN\({}_{5}\)} & \multirow{2}{*}{2.61} & \multirow{2}{*}{34.7} & \multirow{2}{*}{**Donor**} & \multirow{2}{*}{**Acceptor**} \\ \cline{1-1} \cline{6-6}  & & & & & & \\ \hline \multirow{2}{*}{**Chlorpyrifos**} & \multirow{2}{*}{350.575} & \multirow{2}{*}{C\({}_{9}\)H\({}_{11}\)C\({}_{8}\)NO\({}_{3}\)PS} & \multirow{2}{*}{4.96} & \multirow{2}{*}{**1.4**} & \multirow{2}{*}{**Donor**} & \multirow{2}{*}{**Acceptor**} \\ \cline{1-1} \cline{6-6}  & & & & & & \\ \hline \multirow{2}{*}{**Diazinon**} & \multirow{2}{*}{304.345} & \multirow{2}{*}{C\({}_{12}\)H\({}_{21}\)N\({}_{2}\)O\({}_{3}\)PS} & \multirow{2}{*}{3.81} & \multirow{2}{*}{**Donor**} & \multirow{2}{*}{**Acceptor**} \\ \cline{1-1} \cline{6-6}  & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characteristics of Alachlor, Atrazine, Chlorpyrifos and Diazinon [26]. Indeed, for Alachlor, as shown in Figure 1A, the maximum reported removal performance reached 80% for acid-activated beideillite clay particulates grafted with organosilanes for a BET of 221 m\({}^{2}\)/g (Table 2, \(N\)5). In comparison, the largest specific surface area of 608 m\({}^{2}\)/g of an activated charcoal adsorbent removed 40% of Alachlor (Table 2, \(N\)4). Nanofiber adsorbents made of alumina with surface-grafted organosilanes showed the second best performance with 58% removal for a specific surface area of 252 m\({}^{2}\)/g (Table 2, \(N\)1). The higher performance of organosilane-grafted clays and alumina nanofibers suggests that there is competition between adsorption via hydrophobic interactions and via electrostatic interactions as the most efficient mechanism for Alachlor uptake [28,29]. Indeed, organosilane grafting provides the adsorbent with a hydrophobic surface more amenable to pesticides [28]. Each adsorbent reported in this study for the adsorption of Alachlor differs in  
Figure 1: Adsorption removal (%) related to adsorbent specific surface area for different adsorptive structures and for different adsorbent compositions against Alachlor (**A**,**B**), Atrazine (**C**,**D**) and Diazinon (**E**,**F**). both structure and composition. Figure 1B shows the different compositions of Alachlor adsorbents, revealing here a lower performance for carbon-based adsorbents (Table 2, \(N\)3) followed by biomass adsorbents made of kernels and leaves (Table 2, \(N\)6-_N_15). Several factors may explain the lower performance of activated charcoal, such as unsuitable surface pore characteristics not reported in the literature. A different structure than crystalline honeycomb carbon adsorbent may also impact the arrangement and coordination of adsorbate molecules on the charcoal surface, virtually decreasing the proportion in active sites compared to nitrogen adsorption, as well as discourage adsorption by electron interaction due to the absence of unsaturated bonds.