Preparation and application of a new Fenton-like catalyst from red mud for degradation of sulfamethoxazole

In this work, using molasses wastewater as a partial acidifying agent and bagasse pith as a pore-enlarging agent, a new low-cost Fenton-like catalyst (ACRM_bp) used for degradation of sulfamethoxazole was prepared through a simple process of acidification and calcination using red mud (RM) as the main material. The optimum preparation conditions of ACRM_bp were acquired, and the optimum preparation conditions of ACRM_bp were as follows: mass ratio of bagasse pith to RM (m_bp:m_RM) 0.033:1, particle size of bagasse pith 0.10-0.20 mm, calcination temperature 773 K, and calcination time 2 h. The ACRM_bp catalyst was characterized by XRD, SEM, EDS, and BET. According to the results of characterizations, it was found that the iron phase of ACRM_bp had completely transformed into α-Fe₂O₃ after the process of acidification and calcination, and the addition of bagasse pith significantly improved the surface area of the prepared ACRM_bp. Furthermore, under the reaction conditions of catalyst dosage of 2 g/L, initial pH 3 and reaction time 90 min, the ACRM_bp has showed the highest catalytic activity. ACRM_bp had significantly higher activity than red mud, and exhibited a remarkable settleability. Besides, ACRM_bp retained good recyclability and stability during use. Kinetic studies showed the degradation process could be described with the first-order model. Overall, the prepared ACRM_bp was an effective and excellent catalyst in the Fenton-like process.