Introduction and purpose: Two of the most important issues of today’s world are water scarcity and water supply pollution with heavy and toxic metals. We aimed to investigate the removal of aluminum ions from aqueous solutions by modified slag of Khuzestan Steel Company. Methods: Steel slag was prepared from Khuzestan Steel Company in Ahvaz, Iran. This laboratory-scale experimental study was carried out to investigate the removal of aluminum from aqueous solutions using modified slag in discontinuous flow system. The studied variables included pH, adsorbent dose, initial  concentration of aluminum, and reaction time. The concentration of aluminum ions was quantified using atomic absorption spectrometer. In carrying out this study and the use of resources, ethical issues were observed. Results: The results showed that the adsorption capacity of aluminum on modified steel slag is dependent on parameters such as pH, adsorbent dose, initial concentration of aluminum, and reaction contact time. The optimum efficiency was obtained at pH 4, adsorbent dose of 5 g/L, the initial concentration of20 mg/l, and contact time of 60 min. Aluminum adsorption isotherm of modified slag in Khuzestan Steel Company followed the Langmuir model. The best aluminum adsorption kinetics model in this study was shown to be the pseudosecond- order model. Conclusion: In this study, it was found that modified slag of Khuzestan Steel Company is highly potent in aluminum  removal, and it can be utilized as a costeffective adsorbent.