Activated carbons from brewers spent grain improve Orange II removal through combined adsorption and enzymatic oxidation

Abstract

The brewing industry generates large amounts of brewer’s spent grain (BSG), which posesenvironmental challenges due to improper disposal. While BSG has been studied as a dye adsorbent, its conversion into activated carbons (ACs) for dye removal via both adsorption and enzymatic oxidation remains underexplored. Moreover, prior studies rarely distinguish the individual roles of adsorption and enzymatic catalysis in dye removal. This study addresses these gaps by producing eco-friendly ACs from BSG through non-conventional chemical activation and evaluating their dual functionality in Orange II removal using immobilized horseradish peroxidase. Activation at 400–600 °C and NaOH/BSG mass ratios of 1:1 to 3:1 increased surface area (3.46–466 m2/g) and micropore volume (0.001–0.172 cm3/g). The Langmuir–Freundlich model best fit the adsorption data, with ACs activated at 600 °C achieving the highest capacities (19.90–21.79 mg/g). In enzyme-loaded ACs, Orange II removal was 14.70 ± 1.23% by adsorption alone and increased to 22.20 ± 1.12% with H2O2, showing a 51.02% improvement due to enzymatic oxidation. These results demonstrate the synergistic potential of combining adsorption and enzymatic catalysis, offering a novel and sustainable approach for BSG valorization in wastewater treatment.