Adsorption of gas-styrene on activated carbon from agro-waste of Silybum marianum L. as a sustainable precursor

Styrene adsorption has always been a research focus in the field of the gas environment due to its widespread usage. Removal of styrene using activated carbon has been verified because of the physicochemical properties of SMACs prepared by activating Silybum marianum L. waste powder. Hence, a series of novel SMACs were synthesized from NaOH, KOH, and H 3 PO 4 ratio of 1:1–5 w/w and pyrolyzing at 450–950 °C and then washed activated carbon with HCl and NaOH. SMAC82, SMAC137, and the optimal AC (SMAC249) had the largest styrene adsorption capacity, 229, 170, and 136 mg/g for 700 ppm of styrene. Styrene is a typical model for volatile organic compounds (VOCs) in the atmosphere, and the findings demonstrated that it is rapidly absorbed into SMAC82, SMAC137, and SMAC249 through strong physical sorption. The calculated adsorption amounts showed that the styrene capture processes were feasible for adsorption within a suitable contact time and with excellent equilibrium adsorption capacities. Also, the results showed that the highest removal efficiency at 25 °C by the adsorption of SMAC82, SMAC137, and SMAC249 was 92%, 88%, and 86%, respectively. The efficiency results of SMAC82, SMAC137, and SMAC249 show that the styrene breakthrough at 25 °C compared to that of 35 and 45 °C increases approximately two times. Overall, this SMAC82 presented an excellent separation performance for styrene removal and can be a potential option for industrial applications of other VOCs in gas-phase, indicating good adsorption ability.