Valorization of Biomass Hydrolysis Waste: Activated Carbon from Humins as Exceptional Sorbent for Wastewater Treatment

Humins, waste from biomass hydrolysis, are the main factor limiting the utilization efficiency of biomass carbon. In the present study, waste humins were employed for activated carbon production though KOH activation in a temperature range of 500-900 degrees C. The structure and properties of the activated carbons were studied, and a honeycomb-like macropore structure was observed. High activation temperature was demonstrated to be capable of promoting the formation of activated carbon with high surface area, high pore volume and high adsorption capacity. The activated carbon obtained by carbonization at 800 degrees C (KOH800) was selected as sorbent to adsorb methylene blue (MB) and phenol in aqueous solution, and the adsorption process can be explained by pseudo-second-order kinetic model. The adsorption behavior complies with Langmuir isotherm model and exhibits superior adsorption capacity of 1195 and 218 mg/g for MB and phenol, respectively. The impacts of surface area, acidic active sites and pore structures were also investigated, and it was found that the adsorption of approximately 44.0% MB and 39.7% phenol were contributed by the pores with apertures from 1.7 nm to 300 nm.