Abstract:

This study proposes a new model of iron/carbon synergistic catalysis to promote ozone deep treatment for high concentration ammonia nitrogen wastewater (simulated livestock and poultry breeding wastewater, NH₄⁺-N≈550 mg/L) treated by ozone oxidation. Under alkaline conditions (pH=10), a synergistic catalytic ozone treatment was carried out by mixing 10 g/L zero valent iron with 40 g/L activated carbon. The removal rate of ammonia nitrogen reached 85% within 24 hours reaction time and increased to 99.8% within 84 hours reaction time. Results of mechanism analysis showed that: the activated carbon enhanced the generation of free radicals (·OH/·O₂^-) and promoted the conversion of Fe⁰ to Fe²⁺/Fe³⁺ (reducing Fe⁰ on the surface of the iron sheet to 0%); it strengthened the Fe²⁺/Fe³⁺ cycle (increasing the proportion of Fe³⁺ to 30.5% and Fe²⁺ to 69.5%), and increased the formation of iron oxides (increasing the oxygen content on the surface of the iron sheet to 6.26%); in the meanwhile, its microporous structure enriched pollutants and prolonged the contact time of free radicals, forming a synergistic effect of ‘adsorption catalysis’. In a word, this strategy has strong operability and high efficiency, providing a new idea for the deep treatment of livestock and poultry breeding wastewater and high ammonia nitrogen wastewater.

Key words: ozone advanced oxidation, iron/carbon co-catalysis, free radical change, XPS, EPR analysis