Pomegranate peel-derived biochar as ecofriendly adsorbent of aniline-based dyes removal from wastewater

In this study, biochar from pomegranate peels with high specific surface area (423 m(2)/g) and mesoporous character (pore size = 2.42 nm) was prepared, showing a point of zero charge (pH(zc)) of 7.75. This material was used, for the first time, as adsorbent for the removal of aniline dyes. The Artificial Neural Network and Central Composite Design modelization allowed to obtain the optimum conditions for the adsorption of Aniline Yellow (AY: C12H11N3) and Aniline Blue (AB: C38H31N3). For the AY, the pH and temperature were 4.5 and 328 K, respectively. When for the AB, the pH and temperature were 9.5 and 295 K, respectively. The contact time and concentration of dye were the same for both pollutants, 39 min and 94 mg/L, respectively. The maximum adsorption capacities were 222.19 and 214.11 mg/g for the AY and AB dyes, respectively. Based on the kinetic, isothermal, and thermodynamic studies, it was found that the AY and AB adsorption was physical and spontaneous. Besides, the AY adsorption was an endothermic process (Delta H degrees = 16.64 kJ/mol), while the AB adsorption was an exothermic one (Delta H degrees = - 18.71 kJ/mol). Based on XPS results, adsorption mechanisms were proposed. Finally, the application of the optimum conditions for each dye allowed that the adsorption was highly selective with percentages up to 95%. Nevertheless, when the adsorption was performed at normal conditions (neutral pH and ambient temperature), the biochar exhibited typical behavior of universal aniline-based dye adsorbent and the simultaneous adsorption yield did not exceed 75%. [GRAPHICS] .

Automated summary

In this study, biochar derived from pomegranate peels was used for the first time as an adsorbent to remove aniline dyes. The optimum conditions for the adsorption of Aniline Yellow (AY) and Aniline Blue (AB) were determined using Artificial Neural Network and Central Composite Design modelization. The adsorption of AY and AB was found to be physical and spontaneous, with different thermodynamic properties. The application of the optimum conditions resulted in highly selective adsorption with percentages up to 95%.