Fenton-based processes for the regeneration of biochar from Syagrus coronata biomass used as dye adsorbent

The present work aims to evaluate the application of Fenton reaction as a method for the adsorbent regeneration. The adsorbent was obtained by the thermal decomposition of Syagrus coronata endocarp under vacuum at relatively low temperatures (i.e., 400 degrees C and 800 degrees C). The biochar capacity of methylene blue removal was evaluated in function of time of contact, particle diameter and pyrolysis temperature. The biochar was characterized by X-ray diffraction and thermogravimetric analysis techniques. The highest adsorption capacity was 99.4%, obtained for 4.8 g of adsorbent, pyrolysis at 800 degrees C and particle diameter < 0.149 mm. The data obtained from the kinetic studies fitted better to the pseudo-second-order model, while the adsorption isotherms followed Sips model. Fenton regeneration was conducted using a dye saturated biochar with Fenton reagents at different concentrations of Fe2+ (0.5-1.0 mmol L-1) and H2O2 (100-2,400 mmol L-1) in pH = 3.0 for 30 min. A maximum recovery of 19.31% of the adsorption capacity was obtained using Fenton with Fe2+ 1.0 mmol L-1 and H2O2 600 mmol L-1. Therefore, results showed that the biochar of Syagrus coronata endocarp was effective to remove methylene blue from water solution and Fenton reaction is a viable alternative of regeneration process of adsorbent agents.