Self-prepared beaded activated carbons (SBAC) were derived from carbonized phenolic formaldehyde (PF) resins through an optimal activation procedure (900 o C for 4 h) using CO 2 . A commercial BAC (termed KBAC) was adopted to compare with SBAC over physicochemical properties, adsorption performance against methyl ethyl ketone (MEK) and toluene (TOL), and the regenerability using microwave irradiation. Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models showed good fitting results to explain the adsorption equilibrium. The isosteric heat of adsorption was calculated using the Clausius-Clapeyron equation; the parameters obtained from the D-R isotherm indicate that the interactions between adsorbate and adsorbent were mainly due to physisorption. Microwave heating was applied to the regeneration of saturated adsorbents to examine the effect of irradiation power and heating time on the desorption behavior of adsorbate. Within 12 min of microwave irradiation, excellent desorption efficiencies based on gravimetric method were shown, reaching 110.7 ± 14.4, 104.4 ± 2.6, 90.2 ± 2.3, and 85.5 ± 5.7% for MEK-SBAC, MEK-KBAC, TOL-SBAC, and TOL-KBAC, respectively. After an 8-cycle of adsorption/regeneration, the adsorption capacity for SBAC was significantly decreased when loaded with TOL, whereas it was more significant than the virgin sample as loaded with MEK. In contrast, KBAC was able to sustain the adsorption capacity after an 8-cycle of regeneration, proving its stability throughout the microwave heating. Kinetic models were further employed to illustrate the desorption of the adsorbates from BAC samples, showing that intraparticle diffusion in SBAC and KBAC was the rate-limiting step during microwave heating. The core kinetic parameters obtained could provide insights for lab-scale adsorbent beds or practical engineering scale design. In conclusion, this study demonstrates the excellent adsorption performance of SBAC and the feasibility of microwave regeneration of BACs.

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A commercially available beaded activated carbon (KBAC) was selected for combination with a novel electrothermal swing system in examining the Joule heating effects on the physical and chemical properties of activated carbon and its adsorption regenerability at various regeneration temperatures (120, 140, and 160 °C) after saturation by toluene (TOL) and methylethylketone (MEK). The specific surface area (1278 m2 g− 1) and micropore volume (0.48 cm3 g− 1) for KBAC after one adsorption/desorption cycle were slightly reduced, while KBAC micropore surface area (1158 m2 g− 1) and micropore volume decreased significantly after six adsorption/desorption cycles. It can be inferred that the pores of KBAC, especially micropores, are blocked by heel buildup caused mainly by formation of cracked TOL and MEK coke generated by cyclic Joule heating. The desorption efficiencies of TOL-KBAC and MEK-KBAC (KBAC saturated with TOL and MEK, respectively) evaluated per the gravimetric method ranged from 55 to 80 and 85–90%, respectively, and both showed great correlation between regeneration temperature and desorption efficiency. Notably, the desorption efficiencies calculated from the integral method based on breakthrough curves were 8 and 16% lower than those directly obtained by the gravitational method for TOL-KBAC and MEK-KBAC, respectively. The larger difference in desorption efficiency evaluated by the two methods for MEK-KBAC is likely caused by the decomposition of MEK into CO or CO2, which was less prominent in TOL-KBAC. In the cyclic adsorption/desorption tests, the adsorption capacities of both TOL-KBAC and MEK-KBAC decreased after the 6-cycle electrothermal swing regeneration, such that TOL-KBAC adsorption capacity significantly reduced to around 50%, while that of MEK-KBAC retained around 70% of their respective original adsorption capacities. As aforementioned, heel buildup blocks the pores and leads to decreasing adsorption, especially for TOL.

Self-prepared beaded activated carbons (SBAC) were derived from carbonized phenolic formaldehyde (PF) resins through an optimal activation procedure (900°C for 4 h) using CO 2 and compared with a commercial BAC (termed KBAC) over physicochemical properties, adsorption performance against methyl ethyl ketone (MEK) and toluene (TOL), and their regenerability. Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models showed good fitting results. The isosteric heat of adsorption was calculated using the Clausius-Clapeyron equation; the parameters obtained from the D-R isotherm indicate that the physisorption predominates the adsorption process. Microwave heating was applied to regenerate the saturated adsorbents to examine the effect of irradiation power and heating time on the desorption behavior. Within 12 min of microwave irradiation, excellent desorption efficiencies were shown, reaching 110 ± 14.4%, 104 ± 2.6%, 90.2 ± 2.3%, and 85.5 ± 5.7% for MEK-SBAC, MEK-KBAC, TOL-SBAC, and TOL-KBAC samples, respectively. Kinetic models were further employed to illustrate the desorption behavior, showing that intraparticle diffusion in SBAC and KBAC was the rate-limiting step during microwave heating. The core kinetic parameters could provide insights for lab-scale or practical engineering scale design. In conclusion, this study demonstrates the excellent adsorption performance of SBAC and the feasibility of microwave regeneration of BACs.