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

Ahmed M.E Khalil,Fayyaz A Memon,Tanveer A Tabish,Deborah Salmon,Shaowei Zhang,David Butler

doi:10.1016/j.cej.2020.125440

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 all selected 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.

Highlights

Pharmaceuticals have emerged as potential emerging contaminants (ECs) over the last two decades
Effect of contact time and ECs adsorption kinetics Batch tests were conducted for different contact times to acquire kinetic profiles for the six ECs adsorbed onto GI, graphene oxide (GO) and porous graphene (PG) (Fig. 1)
The rate of adsorption decreased upon further increasing the time

Summary

Introduction

Pharmaceuticals have emerged as potential emerging contaminants (ECs) over the last two decades. Their traces are rampant in ground and surface waters, typically at trace levels from ng/L to low μg/L, and even can be omnipresent in drinking waters [1,2]. Groundwater and partially treated water contain pharmaceutical traces typically < 100 ng/l, while treated water has concentrations generally below 50 ng/l [5]. Evidence on their detection and persistence in various natural freshwater resources is increasing worldwide. Pharmaceuticals are generally well characterised, and their impacts are assessed before commercialisation, so their negative effects are expected to result in the endocrine disruption in living organisms and development of antibiotic-resistant bacteria and genes [1,7]

Objectives

Methods

Results

Conclusion