Study of diclofenac removal by the application of combined zero-valent iron and calcium peroxide nanoparticles in groundwater

Abstract

Diclofenac (DCF) is one of the most frequently detected pharmaceuticals in groundwater, posing a great threat to the environment and human health due to its toxicity. To mitigate the DCF contamination, experiments on DCF degradation by the combined process of zero-valent iron nanoparticles (nZVI) and nano calcium peroxide (nCaO2) were performed. A batch experiment was conducted to examine the influence of the adding dosages of both nZVI and nCaO2 nanoparticles and pH value on the DCF removal. In the meantime, the continuous-flow experiment was done to explore the sustainability of the DCF degradation by jointly adding nZVI/nCaO2 nanoparticles in the reaction system. The results show that the nZVI/nCaO2 can effectively remove the DCF in the batch test with only 0.05 g/L nZVI and 0.2 g/L nCaO2 added, resulting in a removal rate of greater than 90% in a 2-hour reaction with an initial pH of 5. The degradation rate of DCF was positively correlated with the dosage of nCaO2, and negatively correlated with both nZVI dosage and the initial pH value. The order of significance of the three factors is identified as pH value > nZVI dosage > nCaO2 dosage. In the continuous-flow reaction system, the DCF removal rates remained above 75% within 150 minutes at the pH of 5, with the applied dosages of 0.5 g/L for nZVI and 1.0 g/L for nCaO2. These results provide a theoretical basis for the nZVI/nCaO2 application to remove DCF in groundwater.

Keywords

• nanoscale zero-valent iron (nzvi)
• nano calcium peroxide (ncao2)
• diclofenac
• fenton-like reaction
• groundwater pollution