Issue 8, 2023

The removal of Cd(ii) by the UV/permanganate process: role of continuously in situ formed MnO2 and reactive species

Abstract

The UV/permanganate process is a novel advanced oxidation process generating hydroxyl radicals (HO˙) and reactive manganese species (RMnS), followed by the formation of nano-sized manganese dioxide (MnO2) with an average particle size of 50–60 nm. Considering the application potential of the in situ formed MnO2, this study focused on the feasibility of heavy metal removal by the UV/permanganate process and Cd(II) was selected as a target. The removal percentage of Cd(II) reached 98.5% by the UV/permanganate process after a 60 min reaction at an initial pH of 6.0, which was much higher than those of SO32−/permanganate and Mn(II)/permanganate processes with the same dosage of permanganate. The in situ formed K-layered birnessite type MnO2 was confirmed to be the key adsorbent of Cd(II), fitting the linear fit stage of the MnO2 adsorption isotherm. According to X-ray photoelectron spectroscopy (XPS) and the adsorption isotherm, Cd(OH)2 was formed during the Cd(II) adsorption via surface precipitation in the UV/permanganate process. The continuous generation of in situ formed MnO2 and its high adsorption capacity are responsible for the gradual complete removal of Cd(II) by UV/permanganate, which shows better performance than the preformed MnO2 with a maximum removal percentage of 55.6% at pH 6.0. RMnS was also critical to the enhanced removal of Cd(II). The Cd(II) removal percentage by UV/permanganate was only slightly decreased by the water matrix such as Ca(II), Mg(II) and natural organic matter. This study provides a better understanding of the multiple roles of UV/permanganate in water treatment, which is a more convenient way to control the formation rate of in situ formed MnO2 for heavy metal removal.

Graphical abstract: The removal of Cd(ii) by the UV/permanganate process: role of continuously in situ formed MnO2 and reactive species

Supplementary files

Article information

Article type
Paper
Submitted
12 Cax 2023
Accepted
19 Qas 2023
First published
20 Qas 2023

Environ. Sci.: Water Res. Technol., 2023,9, 2031-2040

The removal of Cd(II) by the UV/permanganate process: role of continuously in situ formed MnO2 and reactive species

W. Wei, X. Kang, S. Wu, V. K. Sharma, R. Xie, B. Xia, K. Guo and J. Fang, Environ. Sci.: Water Res. Technol., 2023, 9, 2031 DOI: 10.1039/D3EW00345K

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