Preparation of a new Fenton-like catalyst from red mud using molasses wastewater as partial acidifying agent

Abstract

Using molasses wastewater as partial acidifying agent, a new Fenton-like catalyst (ACRM_sm ) was prepared through a simple process of acidification and calcination using red mud as main material. With molasses wastewater, both the free alkali and the chemically bonded alkali in red mud were effectively removed under the action of H₂SO₄ and molasses wastewater, and the prepared ACRM_sm was a near-neutral catalyst. The ACRM_sm preparation conditions were as follows: for 3 g of red mud, 9 mL of 0.7 mol/L H₂SO₄ plus 2 g of molasses wastewater as the acidifying agent, calcination temperature 573 K, and calcination time 1 h. Iron phase of ACRM_sm was mainly α-Fe₂O₃ and trace amount of carbon existed in ACRM_sm . The addition of molasses wastewater not only effectively reduced the consumption of H₂SO₄ in acidification of red mud but also resulted in the generation of carbon and significantly improved the distribution of macropore in prepared ACRM_sm . It was found that near-neutral pH of catalyst, generated carbon, and wide distribution of macropore were the main reasons for the high catalytic activity of ACRM_sm . The generated carbon and wide distribution of macropore were entirely due to the molasses wastewater added. In degradation of orange II, ACRM_sm retained most of its catalytic stability and activity after five recycling times, indicating ACRM_sm had an excellent long-term stability in the Fenton-like process. Furthermore, the performance test of settling showed ACRM_sm had an excellent settleability. ACRM_sm was a safe and green catalytic material used in Fenton-like oxidation for wastewater treatment.

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