Removal of phenol by lignin-based activated carbon as an efficient adsorbent for adsorption of phenolic wastewater

The different lignin-based biomass activated carbons were prepared by KOH activation from three different lignin sources [corn straw lignin (CSLAC), lignosulfonate lignin (LSAC) and bagasse lignin (BLAC)]. And the effects of different lignin sources, activation temperatures and adsorption conditions (adsorbent dosage, adsorption temperature and pH value) on the removal of phenol were systematically investigated. The results showed that different lignin-based biomass activated carbons, the CSLAC-based activated carbon exhibited the highest specific surface area and phenol adsorption capacity. And the CSLAC-T prepared at 800  °C (CSLAC-800) possessed specific surface area of 1679 m2/g, and the adsorption capacity of phenol reached 612 mg/g. The phenol removal rate of CSLAC-T was positively correlated with the specific surface area, and the adsorption rate of CSLAC-T was significantly higher than that before modification. In addition, the kinetic model, isothermal adsorption model and thermodynamic parameters of the three adsorbents were discussed. The results show that the three lignin-based activated carbons had a large adsorption capacity for phenol, which was spontaneous and exothermic adsorption. The adsorption is mainly through the π–π and hydrogen bond interactions, and hydrophobic effect.