Chestnut shells to mitigate pesticide contamination

• Chestnut shells were evaluated as low-cost biosorbent for pesticide removal.
• The citric acid pretreatment increased the removal efficiency of chestnut shells.
• The adsorption process was well-represented by the pseudo-second-order kinetic model.
• Freundlich isotherm described the adsorption equilibrium.
• Column assays reported the viability of the developed biosorbent in continuous mode.

In the last years, the presence of pesticides in aquatic environments has increased mainly as a result of the intensification of agricultural activities. Among the different techniques that can be used to remove these contaminants, the adsorption process can disclose as an appropriate treatment. In this work, chestnut shells were evaluated as a low-cost biosorbent for the pesticides pirimicarb, imidacloprid, acetamiprid and thiamethoxam, widely used in agricultural activities. Furthermore, economic acid pretreatments were evaluated in order to increase the removal efficiency. The highest removal was obtained when chestnut shells were pretreated with citric acid, increasing a 15% of adsorption capacity in comparison to raw chestnut shells. Scanning electron microscopy images, energy disperse spectroscopy analysis, Fourier transform infrared spectroscopy and Boehm method were performed in order to characterize the biosorbent. The new biosorbent was analysed in deep by kinetic and isotherm studies. The values of the correlation coefficients and standard error of estimate indicated that the Freundlich isotherm and pseudo-second-order model fitted well to the experimental data. In addition, the biosorbent showed a good behaviour working in continuous mode. The reported results open a new alternative for the restoration of polluted aquatic environments through the application of this new low-cost biosorbent developed.

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