Removal Efficiency of Pharmaceuticals Using Coffee Residues Biochar Activated with Zinc Chloride and Powdered Activated Carbon

Abstract

Objectives The main objective of this study was to identify the feasibility of ZnCl2 pre-treated biochar derived from coffee residues (C-biochar) as a potential adsorbent for the removal of the pharmaceuticals (i.e., ibuprofen (IBF), atenolol (ATE), and carbamazepine (CBZ)) from wastewater. Methods The removal efficiencies of IBF, ATE, and CBZ by C-biochar and powdered activated carbon (PAC) were compared under different pH (3 ~ 9), temperature (15 ~ 45℃), and ionic strength (0 ~ 0.5 M) conditions and directly correlated to their physicochemical properties to provide deeper insights into the removal mechanisms of the pharmaceuticals by the adsorption processes. Results and Discussion C-biochar was more effective for the removal of IBF and CBZ compared to PAC since it showed the greater surface area (C-biochar = 1048.2 m2/g; PAC = 957.6 m2/g) and pore volume (C-biochar = 1.044 cm3/g; PAC = 0.676 cm3/g). However, the removal efficiency of ATE by PAC was higher than that of ATE by C-biochar due to the differences in their function group composition. The Freundlich isotherm model was well fitted to the adsorption of the selected pharmaceuticals by C-biochar and PAC compared with the Langmuir isotherm model. The removal of IBF and ATE by C-biochar and PAC varied substantially depending on the pH of the solutions as their adsorption phenomena were mainly governed by the electrostatic interaction whereas the effects of pH on the removal of CBZ were not significant because of its high pKa value (14). Furthermore, the adsorption of all the selected pharmaceuticals by C-biochar and PAC was found to be independent of the solution ionic strength. Conclusions This study demonstrated that C-biochar may be utilized as a potential adsorbent for the effective removal of the pharmaceuticals from wastewater due to the greater surface area and pore volume compared to PAC. The removal of IBF, ATE, and CBZ by C-biochar and PAC was strongly influenced by the physicochemical properties of the pharmaceuticals and adsorbents. Key words: Adsorption, Biochar, Coffee Residue, Pharmaceuticals, Powdered Activated Carbon