Bioproducts from the pyrolysis of castor seed cake: Basic dye adsorption capacity of biochar and antifungal activity of the aqueous phase

Abstract

Castor seed cake, a solid residue produced after castor oil extraction, has been used as raw material in the pyrolysis process. Crude biochar (40.6% yield) was subjected to four activation methods; the best activating agent for obtaining activated biochar 1 (AB1) with 603.29 m2 g−1 of a specific area comparable to commercial active carbon in the methylene blue dye adsorption was concentrated sulfuric acid (H2SO4). The adsorption experiments revealed the removal of more than 96% of the dye, kinetic studies showed that a pseudo-second-order (r2 ≥ 0.99) model fitted better with evaluated data and that intraparticle diffusion controls the adsorption rate of the dye by AB1. The aqueous phase (19.2% yield) was lyophilized, and the organic extract contains –N (3%), –O (49%), and –NO (48%) content compounds. The in vitro antifungal activity against the Cryptococcus species was evaluated, and a low concentration of the aqueous phase induced higher growth inhibition in C. neoformans and C. gattii. Therefore, the use of castor seed cake, an environmental waste, in the preparation of an adsorbent material can be considered a low-cost alternative for water treatment when contaminated with the MB dye. Moreover, the aqueous phase, which is a commonly neglected slow pyrolysis by-product, could be an efficient option for decontaminating areas with a high fungal load.