Abstract: With synthesized Mn₃O₄ as adsorbent, the adsorption of Cr(Ⅲ) was investigated as a function of pH, adsorption time, adsorbent dosage and concentration of Cr(Ⅲ), and the adsorption isotherm was also determined. The results indicate that when the initial Cr(Ⅲ)concentration is 10 mg/L, adsorption occurs in the pH scope of 3.0~7.2; when pH=6.5, the adsorption rate can reach 93.7%; if pH＞7.2, Cr(OH)₃ precipitation is apt to occur; at a temperature of 25 ℃ and pH of 5.5, the adsorption of Cr(Ⅲ) onto Mn₃O₄ experiences a process of rapid rise, gradual increase and slowing down, needing 17 hours to finally reach the final equilibrium. The amount of Cr(Ⅲ) adsorbed increases with the increase in Mn₃O₄ addition and Cr(Ⅲ)concentration, and the adsorption isothermal accords with Freundlich equation.

Key words: Mn₃O₄, Cr(Ⅲ), Adsorption