A Promising, Highly Effective Nitrate Sorbent Derived from Solid Olive Mill Residues

Olive mill residues have been valorized by chemical modification with amines to improve their adsorption capacity and to be used as a low-cost bioadsorbent for nitrate removal. The Taguchi method was used to optimize the process. By performing a three-factor analysis with three levels, it was possible to significantly reduce the number of experiments to be performed and to obtain the best working conditions. The results of the Taguchi method showed that the highest adsorption capacity was 110 mg center dot g(-1) with a functionalized biomass dose of 1 g center dot L-1 using an initial nitrate concentration of 500 mg center dot L-1. Field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the surface morphology and study the chemical changes that occurred in the biomass. For the best conditions of the Taguchi approach, the kinetic and equilibrium aspects of the adsorption process were analyzed. The adsorption isotherms obtained were successfully fitted to the Freundlich (R-2 = 0.98) and Langmuir (R-2 = 0.97) models. The kinetics of the process were studied, and the data obtained fit very well to the pseudo-second-order model (R-2 = 0.99). The adsorption values obtained suggest that it is a bioadsorbent with great potential for nitrate retention in aqueous solutions.

Automated summary

Olive mill residues were chemically modified with amines to enhance their adsorption capacity for nitrate removal at a low cost. The Taguchi method was used for optimization, resulting in significantly fewer experiments and identifying the best working conditions. The highest adsorption capacity of 110 mg center dot g(-1) was achieved with a functionalized biomass dose of 1 g center dot L-1 and an initial nitrate concentration of 500 mg center dot L-1. Field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR) were used for surface characterization and analyzing chemical changes. The adsorption process kinetics and equilibrium were studied, successfully fitting the Freundlich and Langmuir models for the adsorption isotherms, and the pseudo-second-order model for the kinetics. The obtained adsorption values suggest that this bioadsorbent has great potential for nitrate retention in aqueous solutions.