High-performance removal of 2,4-dichlorophenoxyacetic acid herbicide in water using activated carbon derived from Queen palm fruit endocarp (Syagrus romanzoffiana)

Abstract

In this work, an activated carbon sample with a high adsorptive performance for the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was prepared from queen palm endocarp (Syagrus romanzoffiana) by pyrolysis process. The activated carbon presented an XRD pattern related to carbon graphite and functional groups such as C-H, CO, O-H. The material particles presented a highly-porous structure, being beneficial to the adsorption process. The activated carbon showed a remarkable specific surface area of 782 m2 g-1 and pore volume of 0.441 cm3 g-1. The solution pH presented a strong influence on the adsorption process, with ideal pH = 2, being the best adsorbent dosage, 0.5 g L-1. The correspondent removal percentage was 95.4%. The pseudo-second-order model represented kinetic data, presenting R2 > 0.992 and MSR< 19.62 (mg g-1)2. The Langmuir model was the most suitable for describing the equilibrium data with the highest R2 (> 0.997) and lowest values of MSR (< 92.04 (mg g-1)2), indicating a maximum capacity of 367.77 mg g-1. The thermodynamic study indicated a spontaneous operation, with ΔG0 ranging from-23.2 to-32.6 kJ mol-1 and endothermic process (ΔH0 = 67.30 kJ mol-1), involving physical interactions in the adsorbent/adsorbate system. The adsorbent could be regenerated by NaOH and used 7 times with the same adsorption capacity. Hence, overall, the activated carbon prepared from the Jerivá endocarp corresponds to a promising adsorbent in removing 2,4-D herbicide in wastewater.