Treatment of Dyes Wastewater by the Catalytic Wet Persulfate Oxidation Process in Reactors Using Red Mud Combined with Biochar as Catalyst

Abstract: Acid-modified red mud supported by peanut shells (MRP) catalysts were prepared for the catalytic wet persulfate oxidation (CWPO) process of dyes wastewater (containing methyl orange (MO), NH-N, and Cr) in batch and continuous fixed bed reactors. Importantly, the influence of NH-N and Cr on the catalytic performance of the MRP catalyst was primarily studied. In the CWPO process, the reactors had a remarkable degradation efficiency (72–97%) of MO in the dyes wastewater. In the batch reactor, with the increase of NH-N concentration (5–20 mg L), the degradation efficiency of MO was maintained at 93%. When NH-N, Cr, and MO coexist, the degradation of MO had slight inhibition with 87.24%, which indicated that MO concentration was still controlled by MRP under the coexistence system, and the order of the removal effect of MRP on the three pollutants in the reactors was as follows: MO > NH-N > Cr. Furthermore, in the fixed reactor, with the increasing of NH-N or Cr concentration, the MO degradation removal decreased to about 84%. The results showed that the degradation effect of MO in a fixed bed is still considerable. Then, the SEM and FTIR results indicated that SO, ·OH, and O generated in the CWPO process and Fe and oxygen-containing functional groups on MRP played a major role on the degradation of pollutants. This study showed that this novel MRP is a promising catalyst with promising applications in composite dyes wastewater. Graphical Abstract: [Figure not available: see fulltext.]