Adsorption process and mechanism of acetaminophen onto commercial activated carbon

The presence of acetaminophen (also known as paracetamol; PRC) micropollutant in water can cause some potential health risks for human. In this study, commercial activated carbon (CAC), which has been oxidized with HNO3 by supplier to increase the oxygen-functional groups, was applied to remove PRC from water. Results demonstrated that CAC is a dominantly mesoporous material (accounting for 76.3%) with large surface area (S-BET = 1284 m(2)/g) and high total pore volume (V-Total = 0.680 cm(3)/g). CAC possessed abundantly oxygencontaining functionalities and low pH(PZC) (4.95). Raman spectrum of CAC indicated that CAC possessed a more disordered structure with a high intensity ratio of D band and G band (I-D/I-G = 2.011). Adsorption study showed that the adsorption capacity of CAC towards PRC was less affected by solution pH value (2.0-10), and ionic strength (0-1.0 M NaCl), and different water matrixes (distilled water, tap water, coastal water, wastewater from water treatment plant, groundwater, and wastewater from beauty salon). The adsorption process occurred rapidly, with around 52% of PRC in solution (similar to 517 mg/L) being removed within 5 min of contact. The Langmuir maximum adsorption capacity of CAC was 221 mg/g under 1.0 g/L of CAC, pH 7.0, 25 degrees C, and initial concentration of paracetamol (similar to 100-1200 mg/L). The pore-filling was the most important mechanism. The SBET and V-Total of CAC after adsorption decreased (by approximately 96% for both) to 45.6 m(2)/g and 0.039 cm(3)/g, respectively. The second important mechanism involved in n-pi interaction was established by a remarkably decrease in the band intensity (the FTIR spectrum after adsorption) at 1630 cm(-1) (the C=O group). Weak pi-pi interaction was confirmed a significant decrease in the ID/IG ratio from 2.011 to 1.947 after adsorption. Hydrogen bonding formations were recommended by decreasing band intensity in FTIR spectrum at 3448 cm(-1) (O-H) and 1045 cm(-1) (C-O). Weak van der Waals force was identified through the study of effect of solution temperature and desorption. Consequently, oxidized CAC can serve as a promising and potential material for efficiently eliminating PRC from water environments.