High-efficiency reactor and its tandem module with Au–Co–CoOx-coated glass beads for continuous-flow reduction of dyeing wastewater

Abstract

The continuous-flow (C-F) reduction process has been limitedly applied in the treatment of dyeing wastewater owing to the weak catalytic performance of the reactors employed. In this work, a small tubular packed reactor and its module are designed, fabricated and used for the C-F reduction of nitro and azo compounds in dyeing wastewater. Here, Au–Co–CoO_x-coated glass beads with superior catalytic activity are chosen as packing materials, prepared without any toxic chemical agents. By means of the reactor, 4-nitrophenol (4-NP) can be completely removed and its removal rate is determined to be 100 μmol h⁻¹. After that, a novel strategy for the tandem module is proposed to further enhance the removal rate of 4-NP. Based on the tandem module, the removal rate of 4-NP can be dramatically boosted to 1900 μmol h⁻¹. Meanwhile, the rate constant for the C-F reduction of 4-NP can reach up to 0.44 s⁻¹. Furthermore, the tandem module displays satisfactory operating stability, reusability and reliability in real water samples. In addition, the tandem module first achieves the C-F reduction of 2-nitrophenol, 3-nitrophenol, methyl red and methyl orange. Clearly, the reactor and its module can effectively extend the application of the C-F reduction process in dyeing wastewater treatment.