Microwave-assisted modification of activated carbon with ammonia for efficient pyrene adsorption

• Through microwave radiation using ammonia method was proposed to modify CAC.
• The modified samples could obtain good basic properties.
• Adsorption of pyrene on CAC and MA-CAC varies from the monolayer to multilayer process.
• The modified samples, especially MA-CAC, showed an enhanced adsorption of pyrene.

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 m2/g for CAC and MA-CAC, whereas the total oxygen-containing groups 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 of pyrene on CAC and MA-CAC varies from the monolayer to multilayer process. The film diffusion could control the adsorption rate of pyrene onto carbons. 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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