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Study of nanochitosan polymer cotransport in the presence of the insecticide cyantraniliprole in porous media under static and dynamic conditions

Papaioannou Konstantinos-Panourgias

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Summary

Water is one of the most valuable elements for the survival of organisms, and its demand has increased significantly in recent years. During this period, water, whether surface or groundwater, has been severely polluted by industrial waste, urban sewage and run-off from agricultural areas. Currently, most technologies available are not effective enough to remove pesticides and dyes from farms to prevent their transport to the subsoil.In order to alleviate the environmental pressure caused by the excessive use of conventional pesticides, it is necessary to consider the existence or creation of a new product that is environmentally friendly and multifunctional. There is a growing interest in polymeric materials such as Nanochitosan, as well as in ways of its application in various fields of science. The unique physicochemical, biological and ecological properties of this material, such as biocompatibility, biodegradability, non-toxicity, combined with its friendly price and high absorption capacity, make its extensive use in various industrial processes imperative.Cyantraniliprole (trade name Exirel) is an insecticide which is widely used in agriculture because of its effectiveness against insects. However, its diffusion into the soil and thus into the water table can cause toxic effects on the environment as well as problems for the ecosystem. There is an urgent need to understand the basic processes and mechanisms involved in the uptake of this pesticide by different soil systems. It is also important to take into account the effects of the pesticide's behaviour on soil and hydrological systems, with a view to protecting the environment. Research and awareness on these issues should be significantly increased nowadays.Adsorption is now recognized as a promising technology which has the capacity to remove pesticides, pigments and other pollutants contained in wastewater. In fact, compared to the other methods available for the purification and treatment of wastewater. physico-chemical or biological methods, adsorption is preferred as a technique due to its simplicity, flexibility, unique design and operation. The advantage of adsorption lies in the fact that it can minimize or even eliminate the toxic by-products produced while at the same time the whole process does not require high investment and operating costs.In the current study, the ability of Nanochitosan to adsorb cyantraniliprole (trade name Exirel) through a porous material is investigated in order to seek an innovative alternative for environmental clean-up and to study the transfer of the contaminant to the soil. Three serial experiments were carried out to collect data. Initially, "Batch" experiments were conducted under static and dynamic conditions in order to investigate the interaction of Nanochitosan with Exirel. Then, the same experimental setup was repeated with the addition of quartz sand, a material that simulates the soil substrate. To conduct the intermittent work experiments, various parameters were chosen to cover a wide variety of conditions encountered in the natural environment.In more detail, various Exirel solutions were prepared at different concentrations (37.5 μL, 75 μL , 150 μL) with the concentration of Nanochitosan remaining constant (50 mg/L) in all experiments. Then, the pH value (4, 6.5, 8) was adjusted and solutions with different ionic strengths (1mM, 50mM, 100mM) were prepared, keeping the temperature constant at 25 °C. Finally, experiments were carried out under packed column conditions with different levels of quartz sand and water velocity in the pores, in order to examine the effect of these factors on the transport of Nanochitosan and Exirel.To form a comprehensive view on the subject, experiments were conducted both with the two materials and separately to study the transport characteristics. The results showed that the solution containing both materials showed the best performance, confirming the significant contribution of the polymer Nanochitosan to the adsorption of the insecticide Exirel (cyantraniliprole) in soil. ColloidFit software (V. Kattzourakis, C. Chrysikopoulos) used to process the experimental data, which simulated the data according to the second-order kinetic model of adsorption. It is therefore noted that the phenomenon that prevailed in all experiments was chemical adsorption.

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