Percolation as new method of preparation of modified biosorbents for pollutants removal

Abstract In the present work, we report the preparation of modified biosorbents from guava seeds, through the conventional and percolation methods, using NaOH solutions, in order to enhance their biosorption capacities. The modified biosorbents obtained from the conventional (MGS-C) and percolation (MGS-P) methods were characterized from the macro-and micronutrient contents, pH drift method, Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). In addition, the biosorbents were applied to equilibrium and kinetic studies for methylene blue (MB) removal. The kinetic models of pseudo-first order, pseudo-second order, and Elovich and isotherm models of Freundlich, Langmuir, Toth, Sips, and Dubinin–Radushkevich were used to evaluate the biosorption experimental data. Kinetic data were best described by Elovich and pseud-second order models for MGS-C and MGS-P, respectively, while biosorption equilibrium data were best fitted by Sips model. The kinetics and isotherm modelling indicated that MB biosorption onto the modified biosorbents occurs in monolayers and the biosorption process is controlled by chemisorption. Moreover, the chemical modification with NaOH provided an increase in the MB biosorption capacity of about 6 times, when compared to the raw biosorbent. The biosorbents MGS-C and MGS-P showed maximum biosorption capacities for MB of 40.26 and 40.90 mg g −1 , respectively, demonstrating that both modification procedures are sufficiently equivalent, being the percolation process the best, since it doesn’t need an extra filtration step.