Nanostructured porous graphene for efficient removal of emerging contaminants (pharmaceuticals) from water

Abstract

Pharmaceutical pollutants have become a worldwide concern. These emerging contaminants (ECs) are ubiquitously found in different water streams with concentrations above ecotoxicity endpoints, deteriorating aquatic life and water quality. This study evaluated extensively the efficacy of porous graphene (PG) synthesised at relatively low temperature as a potential candidate for the removal of six widely utilised pharmaceuticals from their aqueous solutions, such as atenolol (ATL), carbamazepine (CBZ), ciprofloxacin (CIP), diclofenac (DCF), gemfibrozil (GEM) and ibuprofen (IBP). Detailed batch tests were conducted to investigate the effects of adsorption time, initial EC concentration, PG dosage, solution pH, and temperature. Treatment efficiencies of ECs removal by PG were compared with those removed by carbonaceous counterparts (graphene oxide and graphite). Mixed solutions of these ECs were treated in different water bodies to test PG as a tertiary treatment option. The mechanism of adsorption was explored via thermodynamic studies, adsorption kinetics, and isotherm modelling, and characterisation of PG sorbent before and after ECs adsorption using TEM, SEM-EDS, XRD, FT-IR, Raman spectroscopy and other analyses. The results revealed fast kinetics and adsorption capacities exceeding 100 mg-EC/g-PG for some of ECs, and high removal efficiencies for trace concentrations of ECs (>99%) at a low dose of PG (100 mg/L). Removal efficiencies of mixed ECs in water and wastewater samples suffered from negative interferences, which can be mitigated by increasing the PG dosage. Adsorption processes were heterogeneous and controlled by physisorption. Further results showed the exothermic nature of the enthalpy-driven adsorption process and the recyclability potential of PG. It can be considered that PG could be used as a promising candidate for efficient treatment of water contaminated with ECs related to the pharmaceutical group.