| Iodinated X-ray contrast media(ICM)is commonly used in medical diagnosis,its demand is rapidly increasing globally recently.It’s reported that ICM is an important iodine-containing precursorfor iodine disinfection by-products.Because of its water solubility and strong stability,ICM posed an undeniable risk to the aquatic environment and human health.In this paper,Cu(Ⅱ)catalyzed free available chlorine(FC)for removing non ionic ICM-Iopamidol(IPM)was studied,and the recovery possibility of copper ion was explored as well.The main content includes:(1)The experiment compared the initial concentration of IPM at 8 mg/L,under the conditions:rotating speed of 500 r/min,25℃,oxidant dosage of 0.5 mmol/L,initial pH=6.71,metal ion concentration of 0.05 mmol/L,and 60 minutes,compared with Mn(Ⅱ),Co(Ⅱ),Zn(Ⅱ)and Fe(Ⅱ),the Cu(Ⅱ)/FC system showed obvious removal on IPM(77.51%)and the highest FC decomposition ratc(33.04%)respectively.Under the same conditions,the removal rates of IPM by Cu(Ⅱ)catalyzed H2O2 and persulfate(PMS)were only 5.6%and 10.88%.This indicates that the Cu(Ⅱ)catalyzed FC system has a significant synergistic effect and a stronger removal efficiency of IPM.(2)The free radical quenching experiment showed that·OH,Cl2-·,FC and Cu(Ⅲ)contributed to the removal of IPM in the system,and the type and contribution of free radicals are related to pH.When pH=10.00,IPM can be completely removed,with Cu(Ⅲ)contributing more to IPM removal.Under pH=6.71 and pH=10.00,the Cu(Ⅱ)/FC system can achieve the recovery of copper ions with a recovery rate of 96.7%while removing IPM.By analyzing methods such as X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)analysis showed that the recovered product was mainly CuO,and its catalytic ability for FC was weakened.(3)In Cu(Ⅱ)/FC removal of IPM,the IPM removal rate increases with the increase of IFC concentration(0.1～5 mmol/L);As the dosage of Cu(Ⅱ)increases(0.005～0.5 mmol/L),the removal of IPM first increases and then decreases.Among them,Cl-(0～5mmol/L showed a slight inhibition.Br-(0～5 mmol/L)resulted a obvious decrease for IPM oxidation because it consumes FC.HCO3-,I-,and NH4+almost completely inhibited IPM removal evenat low concentrations(1 mmol/L).Humic acid(HA)(5mg/L)promoted IPM oxidationand showed inhibition at concentration of 20 mg/L.(4)HPLC/MS/MS showed that 13 intermediate products was formed during IPM degradation under Cu(Ⅱ)/FC system.And IPM degraded in two ways:(1)Cl2-· and FC attack:side chain amide bonds are gradually hydrolyzed and oxidized,and Cl-replaces Ⅰ ions on the benzene ring.(2)·OH and Cu(Ⅲ)attack:amide partial hydrolysis;Hydroxyl addition on benzene ring.The intermediate products posed certain ecological risks.However,compared to FC,the amount of CHI3 generated in the Cu(Ⅱ)/FC system is 1.29 μg/L reduced to 0.89 μg/L,which reduces the CHI3 yield and showed that Cu(Ⅱ)/FC is a safe way.The Cu(Ⅱ)catalytic FC system proposed in this study has certain reference significance for enhancing the oxidation of organic compounds by chlorine and reducing the generation of iodine disinfection by-products. |
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