Adsorption and desorption of acetylsalicylic acid onto activated carbon of babassu coconut mesocarp

Activated carbon of babassu coconut mesocarp (ACB), which is an environment-friendly material (low-cost), was evaluated as alternative adsorbent for the adsorption and desorption of acetylsalicylic acid (ASA) from aqueous solution. ASA is a non-steroidal anti-inflammatory pharmaceutical easily acquired and prescribed worldwide, and not completely removed by wastewater treatment plants (WWTPs). For this reason, properties of ACB (untreated) were characterized by N-2 adsorption/desorption, FTIR spectroscopy, SEM, Boehm titration method and pH(PZC). The microporous nature of ACB strongly influenced both the adsorption of ASA and the occurrence of physical adsorption bonds, which allows the reversibility of the reaction. ACB surface was rich in carboxylic and phenolic groups. The adsorption was best described by the pseudo-second order kinetic model (89.87 mg g(-1)) at pH 2.0, which represented 80% of ACB adsorption capacity. Conversely, desorption was best represented by pseudo-first-order kinetic model (15.07 mg g(-1)) at pH 6.4, which corresponded to approximately 25% of ASA desorption capacity. Sips isotherm model was best fitted to the equilibrium data of adsorption (50.400 mg g(-1)) at pH 2.0 and desorption (85.213 mg g(-1)) at pH(PZC) 6.4. The negative Delta H degrees showed that adsorption ( - 23.45 kJ mol(-1)) and desorption ( - 5 x 10(5)kJ mol(-1)) were exothermic processes. In addition, the regeneration capability, evaluated through the cycles of reuse, indicated increase of the adsorption and desorption capacities of 53.36% and 32.71%, respectively.