Removal of aspirin from aqueous solution using activated carbon from Kenaf fiber as adsorbent

Abstract

The discharge of aspirin into the wastewater as an emerging contaminant is considered very harmful especially in terms of its teratogenic and fatality effects towards biodiversity. Several methods had been introduced to eliminate this pollutant including the application of activated carbon as adsorbent through adsorption technique. Nevertheless, they are usually made from non-renewable sources derived from charcoal and less environmentally friendly. Thus, researches have explored the perspective of kenaf fiber as effective, renewable, and green adsorbent in aspirin removal process from wastewater. In the context of this research, the adsorbent which was the activated carbon synthesized from the kenaf fiber was prepared. Kenaf fiber was chemically activated with phosphoric acid at impregnation ratio of 1:1, carbonization temperature of 500oC, and carbonization time of 3 hours. The surface properties of adsorbents were characterized by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscope, Brunauer-Emmett-Teller. Thermogravimetric analysis point of zero charge and Energy Dispersive X-Ray spectroscopy. The adsorption process was done in batch mode with different parameters of contact time (0-180 minutes), initial aspirin concentrations (100-500 mg/L), adsorbent dosage (0.1-0.5 g), temperature (30 oC - 60 oC), and pH of aspirin (3-11). The best condition was attained with maximum removal efficiency (92.8%) after 120 minutes at an initial concentration of 100 mg/L, the adsorbent dosage of 0.3 g, pH of 3.45, and temperature of 30oC. Desorption and regeneration studies were conducted to assess the reusability of the adsorbents which indicated that the adsorbents could be used up to three cycles. To evaluate the adsorption mechanism, equilibrium isotherm and kinetic data were determined by using Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models as well as pseudo-first and second-order kinetic models. The adsorption mechanism thus fits well with the Langmuir model and the pseudo-second-order kinetic models, indicating the chemisorption mechanism. Thermodynamic parameters consisting of enthalpy change (?H = - 13.854 kJ/mol), Gibbs free energy change (?G = -1.867, -1.589, -1.239, and -0.662 kJ / mol), and entropy change (?S = -39.337 J / mol K) .Thus, this process had shown that the adsorption process was exothermic and occurred spontaneously. Hence, the high percentage of aspirin removal using Kenaf Fiber – Activated Carbon with a maximum adsorption capacity of 90.05 mg/g was revealed to be better than other adsorbents fabricated from other sources and could become the alternative for aspirin removal.