The presence of high-concentration organic contaminants in wastewater poses considerable risks to the health of both humans and ecosystems. Wet air oxidation (WAO) is an attractive treatment option, but current dilution and retreatment processes do not align with economic and environmental principles. Here we report an external circulation wet oxidation treatment process that utilizes oxidizing liquids to reduce feed concentration. By coupling energy consumption model with computational fluid dynamics model, we explore the optimal parameters for an industrial external circulation reactor. A 90 kt/a external circulation wastewater treatment system has been established, achieving a 21.6% increase in chemical oxygen demand (COD) removal efficiency and a 34.8% reduction in energy consumption. These findings provide a promising pathway for the efficient, low-energy treatment of high-concentration organic wastewater while minimizing freshwater resource consumption.
Synthesis of pyridinic nitrogen-rich polymers is a key step in obtaining high-performance polypyrrole-derived electrocatalysts for the oxygen reduction reaction. A straightforward and controllable synthesis method is highly favored to efficiently manipulate the structural and electronic properties of polypyrrole-derived electrocatalysts. Herein, the strategy for the preparation of poly(2,6-diaminopyridine) (PDAP) is developed with the assistance of an external circulation rotating packed bed (EC-RPB). The polymerization could be divided into two stages: a kinetically fast stage and a rate-determining phase-transfer stage. By using the EC-RPB, the polymerization is sufficiently reduced to 3 h with a conversion rate of over 90% achieved due to accelerated mass transfer in the second stage, exhibiting significant improvement in the common processing for PDAP (∼87% in 12 h). Furthermore, with co-doped iron and manganese species, the obtained catalyst shows a good ORR activity and stability, with up to 0.881 V of half-wave potential in an alkaline environment and 0.718 V in an acid environment. This work proposes a facile and efficient synthesis method for PDAP which could also be extended to the production of other polypyridine-derived electrocatalysts.
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