New mechanistic insight into rapid adsorption of pharmaceuticals from water utilizing activated biochar

Abstract

The presence of emerging pollutants especially hazardous chemicals and pharmaceuticals in aquatic environments is a matter of grave concern to human health and the environment. In this study, coffee bean waste (CBW) was utilized to synthesize pristine (CBW550) and activated (CBW550HPO) biochars for the elimination of diclofenac (DF) and levofloxacin (LEV) from water. A facile two-step approach was used to synthesize CBW550HPO using chemical pretreatment and pyrolysis under N2 purging. BET results of CBW550HPO revealed that chemical pretreatment increased surface area by approximately 160 times compared to CBW550. The calculated ID/IG ratio from Raman spectra confirmed that CBW550HPO had a high functionalized surface. Different operational parameters such as contact time, pH, adsorbent dose, ionic strength, and adsorbate concentration were studied and optimized. Maximum Langmuir adsorption capacity of CBW550HPO was found to be 61.17 and 110.70 mg/g for DF and LVX, respectively. Experimental results demonstrated that presence of NaCl in solution enhanced DF removal efficiency due to the salting-out effect. Electrostatic attraction, π−π bonding, and hydrophobic interaction were prominently responsible mechanisms for the adsorption of DF and LVX. Furthermore, continuous-flow mode studies confirmed that CBW550HPO can be successfully utilized in large-scale treatment applications.