# Nanofiber-Based Materials for Persistent Organic Pollutants in Water Remediation by Adsorption
## 1 Introduction
Adsorption has been considered an alternative method of capture and removal of pesticide molecules from wastewaters [4]. Even though lower decreases in water TOC have been obtained by adsorption compared to AOPs, the effluent toxicity after treatment is still undetermined. However, there is a need for a specific adsorbent material able to combine over 95% removal efficiency, fast kinetics, recyclability and low fabrication cost. Among common materials, activated carbons have been widely used against organic compounds and showed high adsorption capacities for a range of initial contamination varying between 15 \(\upmu\)g/L and 80 mg/L as reported in the literature [4; 14; 15]. However, alternatives are being sought to yield more cost-effective adsorbents. Biomass as an inexpensive but abundant material source for biosportion has been considered, yet the biosorbent non-regenerability and pollutant disposal is of a concern [4; 16; 17; 18]. Over the past decade, nanomaterials have been tested for organic adsorption [19; 20; 21]. Their high surface to volume ratio reduces the required adsorbent dose and favours surface reactivity and therefore adsorption kinetics [19]. Nanofiber webs have been designed as a novel adsorptive material solution for water remediation, to benefit from the increased surface reactivity, with an easy handling and water-stable behaviour, as opposed to free nanotubes and nanoparticles, respectively [22]. Furthermore, electrospinning as a nanofiber web fabrication route ensures a high fiber diameter homogeneity and offers versatile web morphologies design [23]. This paper reviews the employment of nanofibers in the adsorption of selected organic pollutants. The first section is dedicated to common pesticides of moderate hydrophobicity, for water contamination levels over 1 mg/L. Selected pesticides are Alachlor, Atrazine, Chlorpyrifos and Diazinon. The second section concerns the adsorption of disinfectants such as phenol and selected chlorophenols, namely 2- and penta-. As phenol adsorption has been widely reported in the literature, phenol has been included in this study to benchmark the performance of nanofibers in the adsorption of phenolic compounds. Furthermore, this inclusion allows for the investigation of the impact of the molecule chlorine number onto the adsorbent uptake. The last section deals with persistent pollutants,highly hydrophobic, including most of the POPs selected for this study. The pesticides reviewed in this section are aliphatic alicyclic organochlororines Aldrin, Dieldrin, Endrin, Chlordane, Heptachlor, Heptachlor epoxide, and Toxaphene 8. Other types of POP selected include polychlorinated biphenyl (PCBs) 2-, 3-, 4-, 5-, 6-, 28-, 77-. Polyaromatic hydrocarbon (PAH) Phenantrene was also considered in this section for performance comparison. Compared to other pesticide removal by adsorption reviews, the present paper gives exhaustive and up-to-date insight into the performance of nanofibers for the removal of several contaminants of different classes [4; 24; 25]. This study aims to help with the design of an efficient adsorbent for a targeted organic pollutant. Therefore, the influence of adsorbent physicochemical properties and adsorption conditions on the resulting performance was investigated in order to determine a specific range of adsorbent surface properties and advantageous test conditions to favour pollutant capture. Finally, a comparison of the adsorptive performance pondered by the proportion range order between adsorbent dose and initial contaminant concentration was made here to help with the design of a cost-efficient material solution. Adsorbents' surface properties, performance and test conditions are reported in Section 2.3, Section 3.3 and Section 4.3 for the adsorption of moderately hydrophobic pollutants, phenolic compounds and highly hydrophobic pollutants, respectively. When either adsorption capacity or removal efficiency was not reported, it has been calculated from the reported performance result.