Removal of phthalates and pharmaceuticals from municipal wastewater by graphene adsorption process

In this work graphene was used for evaluation of its adsorption behavior and performance in removing phthalate esters and pharmaceuticals in municipal wastewater. Di-n-butyl phthalate (DnBP), di-(2-ethylhexyl) phthalate (DEHP), acetaminophen (ACE), caffeine (CAF), cephalexin (CLX), and sulfamethoxazole (SMX) were emerging contaminants (ECs) with detection frequencies over 92% in a one-year monitoring of the occurrence of ECs in influent samples of a sewage treatment plant in Taiwan. Thus, these ECs were selected as the target contaminants for removal by graphene adsorption process. Experimental results showed that the adsorption isotherm data were fitted well to Langmuir model equation. It was also found that the adsorption process obeyed the pseudo-second-order kinetics. A graphene dosage of 0.1 g/L and adsorption time of 12 h were found to be the optimal operating conditions for the ECs of concern in model solutions in a preliminary study. By using the determined optimal operating conditions for removal of such ECs in actual municipal wastewater, removal efficiencies for various ECs were obtained and given as follows: (1) DnBP, 89%, (2) DEHP, 86%, (3) ACE, 43%, (4) CAF, 84%, (5) CLX, 81%, and (6) SMX, 34%.