# An Overview of Nanofiltration and Nanoadsorption Technologies to Emerging Pollutants Treatment
## 3 Nanotechnological Approaches to the Treatment of Emerging Pollutants  
### Nanofiltration Membranes  
Nanofiltration is considered an economical process to remove several types of contaminants. Nanofiltration uses membranes with a pore size on the nanometer scale and operating pressures in the range of 5-40 bar. In the nanofiltration (NF) process, the solvent is forced through a selective membrane. The pressure difference generated between the feed and the permeate side makes it possible to retain the material in the nanomembrane [45]. Nanofiltration membranes have been used in several sectors, such as water treatment, biotechnology, foods, chemical field, and pharmaceuticals [46].  
Nanofiltration membranes have high permeation for monovalent ions. Moreover, comparing reverse osmosis and nanofiltration membranes, nanofiltration membranes show higher flux [46]. [PERSON] et al. [47] found that nanofiltration rejection efficiencies were very close to those achieved by reverse osmosis membranes for active pharmaceutical compounds. In addition, the nanofiltration membranes showed high desalination capacity and rejection of pharmaceutical compounds (>84.1%).  
Fouling is one of the main disadvantages of filtration processes. The possibility of reacting with the free chlorine from the water treatment makes the natural organic material the main responsible for the encrustation of the membrane [46]. To overcome the fouling, nanotechnological approaches such as the use of metal oxide nanocomposites and hydrophilic polymer coating have been reported [48]. Chitosan also was an excellent antifouling agent. It provided nanofiltration membranes with performance >97% for diphenylhydamine and mebeverine. These results were achieved due to the positive charge of the membrane surface and protonation of drug molecules [49].  
Membrane separation processes can be applied to obtain high-quality reuse water, removing all or part of pharmaceutical products. However, conventional treatment processes have shown low efficiency in removing antibiotics. In this sense, [PERSON] et al. [50] evaluated the nanofiltration membranes' performance to remove inforloxacin from a syn  
Figure 1: Possible sources of emerging contaminants in aquatic resources.  
thetic effluent. In this study, membranes showed high selectivity to nonfloxacin (rejection >87%). The pH affected membrane selectivity (highest nonfloxacin rejection at pH 6.5). pH 6.5 also contributed to the lowest membrane permeability. The authors associated these results with electrostatic interactions between the membrane surface and the ionic species of nonfloxacin.  
Several technological applications related to the development of nanofiltration were patented for removing emerging pollutants in aqueous matrices. Among them, the patent US2021252458A1 [51] describes the development of a composite nanofiltration membrane for treating various impurities, including pesticides and precursors of disinfection by-products, among others. Another invention, CN102874900A [52], refers to a nanofiltration method for removing Perfluorooctane sulfonate present in drinking water, or to document CN201458860U [53] concerning a recycling device for glyphosate present in wastewater using nanofiltration.