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

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), NH3- N, and Cr6+) in batch and continuous fixed bed reactors. Importantly, the influence of NH3- N and Cr6+ 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 NH3- N concentration (5-20 mg L- 1), the degradation efficiency of MO was maintained at 93%. When NH3- N, Cr6+, 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 > NH3- N > Cr6+. Furthermore, in the fixed reactor, with the increasing of NH3- N or Cr6+ 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 SO4 (center dot-), center dot OH, and O-2 (-center dot) generated in the CWPO process and Fe2+ 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.