To remove polycyclic aromatic hydrocarbons effectively, coal-based activated carbon (CAC) was produced by various microwave power modification. Original and modified CAC (MCACs) were characterized by N2 adsorption method, scanning electron microscopy, X-ray photoelectron spectroscopy, Boehm method, and point of zero charge determination. Their adsorption behavior of naphthalene was also investigated. Adsorption equilibrium isotherms, adsorption kinetics, and thermodynamics of naphthalene adsorption on CAC and MCACs were generated. Microwave modification enhanced the basic surface groups of MCACs, extended their Brunauer-Emmett-Teller surface area and pore volume, and varied their distribution of surface oxygen groups. Surface area, pore volume, and functional groups of MCACs were positively related to their naphthalene-adsorption capacity.The adsorption equilibrium of naphthalene on CAC and MCACs needed only 40 min, and this adsorption was fast. Adsorption isotherms revealed that the Freundlich model was applicable to the adsorption process. The adsorption kinetics of naphthalene onto adsorbents was described by pseudo-second-order kinetic model. Naphthalene adsorption was found to a spontaneous and exothermal adsorption process. All these results showed that microwave radiation was an efficient and rapid method of modifying activated carbons. Moreover, MCACs was a promising low-cost and fast adsorbent that can be used to remove naphthalene from aqueous solutions.

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With the aim to enhance the adsorption properties of polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions, coal-based activated carbon (CAC) was modified with three different protocols: i) ammonia treatment (A-CAC), ii) microwave radiation (M-CAC) iii) and combined microwave radiation in the presence of ammonia (MA-CAC). The original CAC and all the modified samples were characterized by SEM, nitrogen adsorption-desorption, Boehm method, point of zero charge, FTIR and XPS. The surface area increased from 764.96 to 1293.78 m 2 /g for CAC and MA-CAC, whereas the total groups containing oxygen decreased from 1.57 to 0.25 mmol/g. The pyrene adsorption capacity of all the modified samples was higher than CAC and the adsorption process for pyrene to the equilibrium needed only 40 min. Adsorption isotherm fitting revealed that pyrene adsorbed from the monolayer process on CAC to multilayer process on the modified samples. The adsorption kinetics of pyrene onto carbons was described using the pseudo-second-order kinetic model. The adsorption capacity of the CAC and modified samples had a good positive correlation with surface area, carboxyl groups, and lactones groups. The modified samples, especially MA-CAC, showed an enhanced adsorption of pyrene opening the way to a more general application as efficient adsorbent for PAHs contaminant.

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This study demonstrates the adsorptive recovery of high-concentration Iopamidol (IOP) from aqueous solution. IOP is a highly valuable X-ray iodinated contrast agent (ICA), and the reuse of the adsorbent activated carbon (AC) is via elution with alcohol. Of the adsorbents selected, coconut powder AC (CPAC) displayed the best adsorption performance for IOP. The results of batch investigation into adsorption kinetics, isotherms, activation energy, and thermodynamic calculations support the occurrence of a physisorption process. The adsorption mechanism has been determined using the intraparticle diffusion model. A Boyd plot has revealed that IOP adsorption onto CPAC was mainly governed by particle diffusion. CPAC also exhibited excellent adsorptive performance toward IOP, which was efficiently eluted and recovered using methanol in a semicontinuous flow system. Moreover, the spent CPAC was efficiently regenerated and reused in five adsorption/desorption cycles. The characterization of CPAC samples by SEM, DRIFT, and TGA shows that IOP is absorbed onto CPAC, leading to significant decreases in the BET surface area and pore volume and shift of the pore diameter. π–π, donor–acceptor complex, van der Waals, and hydrogen-bond interactions are governed by the IOP adsorption. Hydrogen-bond interactions between IOP and alcohols play a crucial role in the desorption process. IOP was completely eluted, and the surface properties of CPAC were recovered after elution in the flow system. This study demonstrates that many benefits can be achieved from adsorption/desorption processes, such as those in wastewater treatment and the recovery of valuable compounds, as adsorbent recycling simplifies the operations and reduces treatment costs.