The impact of contact time on the adsorption capacity of ACW and ACP adsorbents for AR18 removal was shown in Fig. 2(A), it clearly depicts that the removal of the dye by ACW and ACP increases as the contact time increases. The removal of the dye was rapid initially and then slowed down after around 40min for ACW and around 90min for ACP. This trend could be due to the high availability of free active sites at the beginning of the adsorption process, whereas after a specific period of time active siteswill be gradually occupiedwhichwill make the process
of adsorption slower [60]. As showninFig. 2(A), it took almost 45min to reach the equilibrium stage for the ACW while it took almost 90 min to reach equilibrium for the ACP. This could be an indication of the higher
availability of adsorption sites on ACW.