Tailoring activated carbon and carbon black adsorbents for efficient PAH removal

Polycyclic aromatic hydrocarbons (PAHs) in industrial effluents pose severe environmental and health risks due to their carcinogenicity, bioaccumulation potential, and resistance to conventional treatment. This study investigated the effects of nitric acid functionalization and metal ion-exchange on the structural properties and anthracene adsorption performance of activated carbon (AC) and carbon black (CB) as representative carbon-based adsorbents. Nitric acid treatment of CB enhanced mesopore development and introduced oxygen-containing functional groups, improving anthracene removal efficiency from 69 to 74% at a 200:1 feed-to-carbon ratio. Conversely, acid treatment of AC reduced removal efficiency from 60 to 50%, attributed to critical micropore volume effected as confirmed by Brunauer-Emmett-Teller (BET) surface area. Metal ion-exchange reduced adsorption performance in both materials, due to nanoparticle agglomeration and surface area while CB-Ni and CB-Zn retained moderate removal efficiencies of 62% and 66%, consistent with better metal dispersion. A strong linear correlation (R² = 0.9483) between BET surface area and anthracene uptake in ion-exchanged samples confirmed physisorption via van der Waals interactions as the dominant removal mechanism in the absence of surface functional groups. The optimal adsorbent, CB-2N, maintained stable removal efficiency of 70-74.5% over five consecutive regeneration cycles, demonstrating excellent structural durability and reusability. These findings establish rational design principles for carbon adsorbent selection and functionalization in industrial PAH remediation applications.