Efficiency and mechanism of zero-valent iron/nitrilotriacetic acid/peroxymonosulfate system for degrading sulfamethazine

In this paper, the efficiency and mechanism of using nitrilotriacetic acid(NTA) as a complexing agent to enhance the zero-valent iron(Fe 0 )/peroxymonosulfate(PMS) system to remove sulfamethazine(SMZ) from water are discussed. Research results show that the addition of NTA increases the soluble iron by 3.05 times, and the decomposition rate of PMS increases from 27% to 62%. Keeping other conditions unchanged and increasing the concentration of PMS to 0.2 mM, the degradation rate reaches the peak, continued increase of PMS concentration will decrease the degradation rate. The degradation rate of SMZ is positively correlated with Fe 0 concentration. The effect of different inorganic ions on the degradation of SMZ was investigated. The high concentration of Cl − promoted the degradation effect, and the reaction rate constant of the system is increased by 1.67 times when the Cl − dosing is 10 mM. The PMS/Fe 0 /NTA system degrades SMZ up to 79.36% in actual water bodies. The degradation of SMZ is mainly by Smiles-type rearrangement, sulfonamide bond breaking, etc. The toxicity test proves that the inhibition rate of luminescent bacteria before and after degradation decreases from 61.86% to 40.47%, with an overall decreasing trend of toxicity.