adsorption intensity, respectively. If the value of 1/n is lower than 1, it indicates a normal Langmuir isotherm: Otherwise, it is indicative of cooperative adsorption [41]. The corresponding isotherm parameters from both models are listed in Table 3. The adsorption of ARS was well fitted to the Langmuir isotherm model with the higher R (0.998). It indicated the adsorption took place at specific homogeneous sites within the adsorbent forming monolayer coverage of ARS at the surface of the adsorbent. The Freundlich constant 1/n was smaller than 1, indicating a favorable process (Table 3). The adsorption isotherm process favorability was also checked using the dimensionless separation factor (R) and the values were calculated using the following equation [42]: