# Nanofiber-Based Materials for Persistent Organic Pollutants in Water Remediation by Adsorption
## 1 Introduction  
Organic water pollution from synthesized chemical pesticides has been increasing over the past 50 years [1]. As a counter-measure, 21 non-polar organic molecules have been classified as persistent organic pollutants (POPs) by the Stockholm Convention (2001, 2017), to be banned or restricted globally [2]. Organochlorines (OCs) account for a large group of POPs, including aldrin or DDT pesticides, but also industrial chemicals such as the family of polychlorinated biphenyls (PCBs), as well as byproducts [1]. The list of POPs also includes several organophosphorus (OPs) pesticides, and among recently added compounds, flame retardants and polyaromatic hydrocarbons (PAHs) [1,2]. The release of POPs is associated with major toxicity concerns for both the environment and human health [3,4]. Their partial degradability affects the chemical oxygen demand (COD) of streams, causing oxygen depletion by consuming oxygen at a greater rate than its replenishment [4]. For some POPs, such as Heptachlor, it is the compound formed after reaction in water, Heptachlor epoxide, that causes threat to human life [5]. The persistency of POPs in the environment can be measured by their half-life duration (DT50). For instance, organochlorine DDT pesticide has a DT50 that, depending on the environment, ranges from 2 to 15 years [6]. The presence of POPs in the environment also affects human health, through the ability of POPs to bio-accumulate in organisms and bio-magnifythroughout the food chain [3]. Exposure of humans to POP can eventually occur through drinking water, via the leaching of pollutants from treated soil into aquifers. Detected levels of POPs in human blood were shown to lead, in some scenarios, to reproductive disorders, immune system alteration, and/or increased risk of cancer [3]. Long-range transportability is another concern associated with POPs [7; 8; 9]. As most POPs are semi-volatile compounds, they are able to cycle among air, water and soil [8]. Characteristics such as subcooled liquid vapour pressure and octanol-water (log K\({}_{\mathrm{ow}}\)) partition coefficients, the latter defining the molecule hydrophilicity as well as temperature of condensation, enable the determination of the mobility of a persistent pollutant through a transportation cycle in the atmosphere, ocean or soil [7; 8]. Warm temperatures, as experienced in tropical regions, enable the evaporation of POPs, while colder temperatures, at higher latitudes, enable the deposition of POPs from the atmosphere onto the ocean or continent [7]. POPs emitted in tropical to temperate regions may therefore be transported to one of the Earth poles, via successive evaporation-deposition cycles, also called the grasshopper phenomenon, determined by seasonal temperature changes at temperate latitudes. POPs emitted at high latitudes, however, are less subject to mobility due to lower temperatures [7]. Polar regions therefore act as an environmental sink for POP compounds [7; 9]. However, as global warming is strongly affecting the polar climate, the possibility of a reverse in the deposition cycle of POP raises concerns [9]. To limit the environmental sink effect, local removal techniques must be put in place to remove pesticides from water. Advanced oxidation processes (AOP), including ozonation, enzyme digestion or catalysis, have been sought after to combine efficiency and fast kinetics [10; 11; 12]. These processes offer to date the most efficient alternative to conventional treatments, in terms of reduction of the total organic carbon (TOC) count in contaminated effluents. Several reviews cover the organic pollutant water decontamination via AOPs and provide a performance benchmark for this study [11; 12]. The main roadblock to the implementation of AOPs is the increase of the effluent toxicity after treatment. For instance, the catalytic degradation of the triazine molecule Atrazine may release carcinogen amine groups in water [13].