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In this study, a manganese oxide, Mn₃O₄ was used to remove chromium(III) and chromium(VI) from aqueous solutions. The Mn₃O₄ nanomaterial was synthesized through a precipitation method, and was characterized using XRD, which confirmed the material had a crystal structure similar to hausmannite. In addition, using Scherrer’s equation it was determined that the nanomaterial had an average grain size of 19.5 ± 1.10 nm. A study of the effects of pH on the binding of chromium(III) and chromium(VI) showed that the optimum binding pH was 4 and 3, respectively. Batch isotherm studies were performed to determine the binding capacity of chromium(III), which was determined to be 18.7, 41.7, and 54.4 mg/g respectively for 4, 21, and 45 °C. Chromium(VI) on the other hand had lower binding capacities of 2.5, 4.3, and 5.8 mg/g for 4 °C, 21 °C, 45 °C, respectively. Thermodynamic studies performed indicated the …