Adsorption of ferulic acid from an alkali-pretreated hydrolysate using a new effective adsorbent prepared by a thermal processing method.

A new adsorbent (AEPA250) was prepared using the enzymatic hydrolyzed residue of rice straw in an air environment at 250 ℃ by a thermal processing method. Compared to the commercial adsorbent, AEPA250 possessed a larger specific surface area of 277.680 m2 g-1, and the maximum adsorption efficiency of ferulic acid from alkali-pretreated hydrolysate of rice straw achieved 70.33 % at the optimum conditions. Adsorption kinetics and isotherm studies showed that the pseudo second-order (PSO) (0.997 ≤ R2 ≤ 0.999) and Liu models (0.931 ≤ R2 ≤ 0.997) exhibited better fitting results, which indicated that chemical and saturable adsorption existed between ferulic acid and AEPA250. An adsorption thermodynamics study revealed the spontaneous and endothermic adsorption process (ΔHo > 0 and ΔSo< 0). Micropore diffusion was defined as the major adsorption rate-limiting step according to the analysis of Webber-Morris and Bangham's model. Additionally, π-π*, ion exchange, hydrogen bonding and precipitation were recognized as the four main mechanisms of ferulic acid removal by AEPA250 through SEM/EDX, EDX mapping, XPS, FTIR and XRD analysis. These results indicated that AEPA250 was effective for adsorbing inhibitors in pretreated rice straw hydrolysates, and it has high potential for application in establishing the self-sufficient production process of bioethanol.