Mechanism and Efficiency of Tetracycline Removal by Ferrate and Ferrous-Enhanced Ferrate System

Ferrate fortified with ferrous iron can effectively improve the degradation of tetracycline (TC) in the coagulation process. Optimizing experiment conditions is investigated in the ferrate and ferrate-ferrous system. TC removing was up to 85% when the molar ratio of ferrate to TC was 2.5:1 under initial pH 4-9. Ferrate-ferrous performance is better than only ferrate or ferrous, and the morphology and composition of flocs formed by the ferrous and ferrate-ferrous systems are investigated. The initial pH has an influence on the coagulation process, whether in the ferrous or ferrate-ferrous system. The stability of flocs created by the ferrate-ferrous system under alkaline conditions was better than that under acidic conditions. Nevertheless, flocs formed by ferrous under acidic conditions were better than that under alkaline conditions. The flocs' stability is related to their composition and structure. The proportion of a-FeOOH formed by Fe(VI)-Fe(II) was approximately between 26% and 37.3%, and the proportion of gamma-FeOOH was 63 similar to 74%. The knowledge obtained in this research enhances the flocculation effect of ferrate and its ability for sustainable oxidative degradation of pollutants.

Automated summary

Ferrate fortified with ferrous iron is effective in enhancing the degradation of tetracycline (TC) during the coagulation process. The optimization of experimental conditions in the ferrate and ferrate-ferrous system is investigated. The removal of TC reaches up to 85% at a molar ratio of ferrate to TC of 2.5:1 under initial pH 4-9. The performance of the ferrate-ferrous system is superior to that of ferrate or ferrous alone, and the morphology and composition of flocs formed by ferrous and ferrate-ferrous systems are examined. The stability of flocs is influenced by the initial pH, with better stability under alkaline conditions for the ferrate-ferrous system and better stability under acidic conditions for ferrous. The stability of the flocs is related to their composition and structure, with approximately 26% to 37.3% of α-FeOOH formed by Fe(VI)-Fe(II) and 63% to 74% of γ-FeOOH. The knowledge gained from this research enhances the flocculation effect of ferrate and its ability for sustainable oxidative degradation of pollutants.