Study of the competitive effect on the adsorption of phenol and 4-nitrophenol in a batch reactor and fixed-bed column using coconut shell activated carbon

In this study, the kinetics and isotherms of mono- and multi-component adsorption of phenol (PN) and 4-nitrophenol (4NP) in aqueous solution were determined in a batch reactor, followed by tests in a fixed-bed column. The adsorbent used was coconut shell activated carbon. The characterization of the adsorbent showed a suitable surface area (724 m2 g−1), pore volume (0.39 cm3 g−1), and average pore diameter of 21.35 Å. Surface characterization revealed the predominance of basic surface groups resulting from the physical activation process. In the monocomponent kinetic assays, PN was completely removed in 25 min, whereas 4NP took 45 min. In the case of multi-component kinetics, both PN and 4NP exhibited an antagonistic effect on adsorption, requiring more time for the compounds to be removed from the solution (PN - 50 min, 4NP - 60 min). For phenol, the adsorption isotherms followed the Langmuir model, and the adsorption was exothermic. On the other hand, the adsorption of 4NP was represented by the Freundlich model, indicating exothermic multilayer adsorption. For the multi-component results, the best fit was the multi-component Freundlich model. The results showed that in both mono- and multi-component systems, 4NP had a higher adsorption capacity and was more competitive for the active site of the adsorbent. Continuous system assays corroborated the data obtained in the batch reactor. The breakthrough curves clearly showed the antagonistic effect of 4NP on the adsorption of PN onto coconut shell activated carbon. •High adsorption capacity with a surface area of 724 m2 g−1.•Rapid removal of PN (25 min) and 4NP (45 min) in single-component assays.•Antagonistic effect extending removal times in multi-component assays.•PN follows the Langmuir model while 4NP follows the Freundlich model.•4-nitrophenol was more competitive in continuous flow.