Enhanced Cr (VI) removal with Pb (II) presence by Fe²⁺-activated persulfate and zero-valent iron system

ABSTRACT

Combined heavy metals such as chromium (Cr (VI)) and lead (Pb (II)) in natural water have globally posed severe environmental and public health risk. Here the removal of Cr (VI) and Pb (II) mixed pollutants using Fe²⁺-activated persulfate (PS) with extra zero-valent iron (ZVI), which was not only a supplementary Fe²⁺ source, but also a high-efficiency absorbent, was investigated. During removal, pivotal factors of initial pollutant concentration, dosages of ZVI and PS, initial pH and temperatures were examined. Interestingly, generating a lot of H⁺ in the process of Fe (II) activating persulfate were helpful to the corrosion of ZVI over a large range of pH (1–9). Under the optimum condition, removal efficiency of Pb (II) and Cr (VI) have reached 100% and 94.26% respectively. The removal mechanism was suggested as a three-step reaction that the Pb (II) boosted the removal of Cr (VI) by co-precipitated in wastewater, and the Pb (II) and Cr (VI) were adsorbed and subsequently reduced to Pb⁰ and Cr³⁺ as Cr(OH)₃ or Cr³⁺-Fe³⁺ hydroxides on ZVI surface. Cr (VI) and Pb (II) adsorption kinetics agreed with the pseudo-second-order reaction rate expression. In addition, we were surprised to found that the contribution effect of chromium and lead co-precipitation for their removal by Fe (II) – PS-ZVI has strong dependence on initial pH and concentration ratio of Cr (VI) and Pb (II). The result indicated that Fe (II)-PS-ZVI system should be a favourable removal technology for Cr (VI) and Pb (II).

GRAPHICAL ABSTRACT

KEYWORDS:

• Chromium (VI)
• Fe (II)-PS-ZVI
• lead (II)
• adsorption
• precipitate

Acknowledgements

The authors want to thank Lina Li and Yuntao Shang for their support with analyses. A portion of this work was performed on the Steady High Magnetic Field Facilities, CAS.

Data availability statement

The data that support the findings of this study are available on request from the corresponding author.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was financially supported by the Youth Scientific Research Talent Support Program of Tianjin Normal University [grant number 135202RC1706], Young and Middle-aged Backbone Innovative Talents Training Project Foundation of Tianjin [grant number 135205GC51], the Second Level Candidates for the “131 Talent Plan” in Tianjin [grant number 135305QR06], National Natural Science Foundation of China [grant number 21307090] and Natural Science Foundation of Tianjin, China [grant numbers 18JCYBJC96600 and 14JCZDJC41000].