Valorization of olive endocarp from olive oil and table olive processing as a low-cost bioadsorbent for the removal of furfural from aqueous solutions

Abstract

Furfural presence in fermentation culture media provokes an inhibition effect in yeast growth. In fact, is a key toxin in lignocellulosic hydrolyzates. This research work attempts to analyze the use of olive endocarp (OE) as adsorbent to remove furfural from aqueous solutions. The adsorption experimental sets studied the effect of particle size, agitation speed, adsorbent load, temperature, and initial furfural concentration. As results, higher adsorption percentages were observed when fragmented OE was smaller than 1.2 mm, agitation speed in the range 80–250 rpm, and the adsorbent load was 90 g OE/300 cm3 of furfural solution (1 g dm−3). The equilibrium adsorption capacities, qe, values were varied from 0.270 to 4.750 mg g−1 for initial furfural concentrations of 0.78 g dm−3 to 5.89 g dm−3. The adsorption data fit to pseudo-second order kinetic model showed good fit values (R2 ≥ 0.997, SE ≤ 5%). Dubinin-Radushkevich (DR) model was considered as the best fit (R2 = 0.999, SE = 2.95%) for the different studied isotherms. An adsorption free energy value of 896 J mol−1 indicated a physical adsorption mechanism. Remarkable increases in furfural adsorption percentages have been achieved submitting natural olive endocarps to acid treatments.