# An Overview of Nanofiltration and Nanoadsorption Technologies to Emerging Pollutants Treatment
## 3 Nanotechnological Approaches to the Treatment of Emerging Pollutants
### Nanoadsorbents
#### 3.2.2 Metal-Based Nanoadsorbents  
Metal-based nanoadsorbents are inorganic nanomaterials widely used for contaminant removal. The commonly used are metal oxides such as iron oxide, silica, magnesium oxide, manganese oxide, zinc oxide, aluminum oxide, and titanium oxide [54; 55]. In addition to the high surface area, these materials have a specific affinity, low solubility, low environmental impact, and do not cause the formation of secondary pollution [55]. Magnetic nanomaterials, such as magnetic iron oxide nanoparticles, have also been used as adsorbents. These materials are easily separated from the solution due to their magnetic properties [82; 83]. Another metal-based nanomaterial investigated is the metal-organic framework (MOF)-based nano adsorbents. Some MOF applied for mitigation of emerging pollutants are Zr-biphenyldicarboxylate (UiO-67), Zn-2-methylimidazololate (ZIF-8), and metal-benzetricarboxylate (MIL-100). Furthermore, these nanomaterials \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**adsorbent** & **Modification** & **Adsobrate (Contaminant)** & **Adsoorption Capacity (mg g\({}^{-1}\))** & **Mechanism of Adsorption** & **Reference** \\ \hline Multi-walled carbon nanotubes (0.2 g L\({}^{-1}\)) & Functionalized with & Atrazine herbicide & 40.2 & \begin{tabular}{c} Hydrogen bonding, \\ Van der Waals forces, \\ and hydrophobic \\ interactions \\ \end{tabular} & [79] \\ \hline Graphene oxide (0.5 g L\({}^{-1}\)) & Functionalized with & & & & \\ magnetic iron oxide & & & & \\ nanoparticles and & & & & \\ cobalt oxide & & & & \\ nanoparticles & & & & \\ \hline Graphene oxide & & & & \\ (0.15 g L\({}^{-1}\)) & & (8–40 mg L\({}^{-1}\)) & 96.8 & \
\begin{tabular}{c} \(\pi\)-\(\pi\) interaction and \\ hydrogen bonding \\ \end{tabular} & [80] \\ \hline Graphene oxide nanosheets & & 17\(\beta\)-Estraediol & 149 &
\begin{tabular}{c} \(\pi\)-\(\pi\) interaction and \\ hydrogen bonding \\ \end{tabular} & [71] \\ (0.1 g L\({}^{-1}\)) & & (0.05-4 mg L\({}^{-1}\)) & & & \\ \hline  & & & & \\ \hline Carbonazepine & & 147 & & \\ (0.1-100 mg L\({}^{-1}\)) & & & & \\ \hline Porous reduced graphene & & & & \\ oxide (0.25 g L\({}^{-1}\)) & & & & \\ \hline Dclofenac & & & & \\ (0.1-100 mg L\({}^{-1}\)) & & 76 & & \\ \hline Gemfibrozil & & & & \\ (0.1-15 mg L\({}^{-1}\)) & & 40 & & \\ \hline Ibuprofen & & & & \\ (0.1-21 mg L\({}^{-1}\)) & & & & \\ \hline  & & & & \\ \hline  & & & & \\ \hline  & & & & \\ \hline Metal-organic framework & & & & \\ (MOF) MIL-101 (0.2 g L\({}^{-1}\)) & & & & \\ \hline  & & & & \\ \hline Metal-organic framework & & & & \\ (30 mg L\({}^{-1}\)) & & & & \\ \hline Aluminum-based & & & & \\ metal-organic framework & & & \\ (Al-MIL-53) (2.6 g L\({}^{-1}\)) & & & & \\ \hline  & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._have a high capacity for regeneration and reuse, contributing to water and wastewater treatment efficiency [84]. The predominant mechanisms for contaminants adsorption by metal-based nanomaterials are electrostatic interactions, Lewis acid-base interactions, hydrogen bonding, and \(\pi\)-\(\pi\) interactions [84]. Electrostatic interactions were the main mechanism of interaction between MOF and pharmaceutical and personal care products such as naproxen and clofibric acid, and the herbicide 2,4-dichlorophenoxyayacetic acid. The interaction occurred between the positively charged adsorbent and the negatively charged contaminant [85]. [PERSON] et al. [68] investigated the interaction mechanisms between the adsorbent aluminum-organic framework with amino-group and the organophosphate insecticide dimethoate. The authors reported hydrogen bonds between the oxygen of the phosphate and the hydroxyl hydrogen of the MOFs, as well as between the amine hydrogen and the sulfur atom of the dimethoate. Electrostatic interactions were also observed. [PERSON] et al.