Influence of activated carbon surface chemistry on the removal of pharmaceutical compounds from water

Abstract

"In the present work the surface chemistry of a commercial AC (NucharA74) was modified by thermal treatments at 500 ºC (NucharA74/500) and 800 ºC (NucharA74/800) under N2 (see pHPZC values on Table 1). The textural properties of the materials were characterized by N2 adsorption at -196 ºC and FTIR spectra. Materials were tested for the simultaneous removal of three PhCs (100 μg/L) spiked in mineral aqueous solution. PhCs were selected considering their worldwide occurrence and persistence in wastewater treatment plant (WWTP) effluents (validated in LIFE IMPETUS, www.life-impetus.eu) and adsorption key-properties: carbamazepine (CBZ - neutral, hydrophobic), diclofenac (DCF - anionic, relatively hydrophobic) and sulfamethoxazole (SMX - anionic, hydrophilic). Concerning PhCs, DCF and CBZ were the most adsorbable compounds. The lower adsorbability of SMX may result from its hydrophilic character and higher polar surface area. The adsorptive capacity was generally more efficient for NucharA74/800, followed by NucharA74/500. The good performance of NucharA74/800 was attributed to its pHPZC value, as it has a lower negative net surface charge density than the other ACs. NucharA74/500 material, despite its high acidity and slightly smaller microporous volume than that of NucharA74, showed a higher adsorption capacity for all PhCs. Thus, the changes on the surface chemistry during the thermal treatment of NucharA74/500 may have favoured the adsorbent-adsorbate interactions, compensating the electrostatic repulsions. "