Efficient removal of bisphenol-A by ultra-high surface area porous activated carbon derived from asphalt

An ultra-high surface area porous activated carbon derived from low cost asphalt (AS) was synthesized and investigated for removal of bisphenol A (BPA), a common endocrine disrupting chemical (EDC) in wastewater and natural waters. Adsorption isotherms, kinetics and thermodynamics of BPA adsorption were determined and benchmarked against commercially purchased Darco G-60 activated carbon (AC). The surface area of AS was 3851 m2/g, which is 4.7-fold larger than that of AC (i.e., 813 m2/g). This correlates well with the 4-fold higher maximum BPA adsorption capacity on AS (1113 ± 52 mg/g), and is consistent with the similar surface functionality of AS and AC (determined by Fourier-transform infrared spectroscopy). The maximum BPA adsorption capacity of AS is highest among reported carbon materials. BPA adsorption kinetics by both materials was limited by slow intraparticle diffusion into the small mesopores and micropores, which resulted in slightly slower adsorption rate for AS that had a greater proportion of micropores than AC. Thermodynamic analysis corroborated that BPA adsorption was favorable and occurred predominantly through π-π interaction as indicated by Raman spectroscopy. Overall, AS is a highly efficient adsorbent for removal of EDCs for water purification and could be considered for drinking water treatment and wastewater polishing.