# Treatment of Water Contaminated with Diesel Using Carbon Nanotubes
## 1 Introduction  
Environmental pollution is a consequence of both civil and industrial anthropic activities and, as such, is highly widespread, even affecting areas of great naturalistic value. It does not spare soils, groundwater [1, 2, 3], surface waters, marine environments [4, 5, 6, 7] and atmosphere [8, 9]. The impact of pollution often has very serious consequences on human health [10], the balance of ecosystems, the livability of habitats, food chains [11, 12], the landscape, the soils, the agriculture and, last but not least, biodiversity as a whole [13, 14]. In recent years, in order to stem and contrast environmental pollution, research has been carried out in various sectors, such as in the production of eco-sustainable materials [15, 16, 17, 18, 19], in the synthesis and preparation of new photodegrading materials capable of degrading pollutants [20, 21, 22, 23, 24, 25] and adsorbents for water purification [26, 27, 28]. The problem of contaminated sites assumes an extremely relevant importance in the context of environmental risk and public health [29]. Soil pollution from petroleum products can mainly affect the soil and subsoil [30, 31, 32]. The main mechanisms that arise when the contamination affects the surface area are: wind transport, oxidative/photochemical degradation, leaching and transport by meteoric or surface water, with the possibility of penetrating the subsoil. Penetrating into the subsoil, a petroleum product in the liquid phase tends to drain due to gravity: the air and the interstitial water are displaced with the consequent establishment of transport, transformation and interaction phenomena, which are a function of the characteristics of the soil and of the chemical-physical properties of the individual pollutants. The penetration of pollutants into the subsoil depends on the soil structure and the type of substance. A sandy soil will be more vulnerable to polluting agents, while a clayey soil will act as an obstacle,although, due to industrialization, the number of chemical substances that can penetrate the soil and consequently the underlying groundwater has significantly increased [33; 34; 35]. Diesel fuel is a common fuel, consisting of a mixture of liquid hydrocarbons, from 13 to 18 carbon atoms. It is obtained via the fractional distillation of petroleum with an average outlet temperature from the fractionation tower of approximately 350 \({}^{\circ}\)C and a higher flash point than petrol. It was used for the first time in the motoring field, as fuel for diesel engines, between 1893 and 1897 by [PERSON], in the experimentation phases that led to the development of the engine that still bears his name. There are numerous cases of accidents involving significant contaminations of diesel or, in general, of other fuels of petroleum origin. Spills at sea and in coastal areas, due to the capsizing or standing of tankers, represent the most striking situations in terms of the seriousness of the damage caused to the environment, although the problem, albeit to a lesser extent but more frequently, also affects other sectors of transport. Transportation, transfer and storage represent situations in which diesel fuel may accidentally spill into the environment [36; 37; 38]. The treatment of environments contaminated with accidental oil spills is often very expensive and difficult. In recent years, research and studies have been carried out to improve and develop new methods for the rehabilitation of areas contaminated with hydrocarbons. Generally, the main methods of remediation of areas contaminated with hydrocarbons are based on biological, chemical and physical phytoremediation treatments. Constructed wetlands, as is known, use plants for the decontamination of polluted sites. However, it is a method that can hardly be used in cases that require an immediate decontaminating action [39; 40]. Biological treatments use indigenous microorganisms for the biodegradation of hydrocarbon pollutants.