Abstract
Application of zero-valent iron nanoparticles (nZVI) for Zn2+ removal and its mechanism were discussed. It demonstrated that the uptake of Zn2+ by nZVI was efficient. With the solids concentration of 1 g/L nZVI, more than 85% of Zn2+ could be removed within 2 h. The pH value and dissolved oxygen (DO) were the important factors of Zn2+ removal by nZVI. The DO enhanced the removal efficiency of Zn2+. Under the oxygen-contained condition, oxygen corrosion gave the nZVI surface a shell of iron (oxy)hydroxide, which could show high adsorption affinity. The removal efficiency of Zn2+ increased with the increasing of the pH. Acidic condition reduced the removal efficiency of Zn2+ by nZVI because the existing H+ inhibited the formation of iron (oxy)hydroxide. Adsorption and co-precipitation were the most likely mechanism of Zn2+ removal by nZVI. The FeOOH-shell could enhance the adsorption efficiency of nZVI. The removal efficiency and selectivity of nZVI particles for Zn2+ were higher than Cd2+. Furthermore, a continuous flow reactor for engineering application of nZVI was designed and exhibited high removal efficiency for Zn2+.
Highlights
Zinc is one of the trace elements closely related to human health
Characterization of Nanoscale zero-valent iron (nZVI) Three kinds of nZVI particles were analyzed by transmission electron microscopy (TEM)
The higher removal efficiency was observed in the experiment with an initial pH value of 5
Summary
Zinc is one of the trace elements closely related to human health. It is essential for living organisms [1]. Excessive amount of zinc in the environment is toxic to man, animals and plants. Zinc toxicity to aquatic organisms and ecosystems has been frequently reported [5,6]. Excessive zinc may lead to the death of fishes [7]. Irrigation water containing excessive zinc may cause poor crop growth and affect the health of the eaters [8,9]. Zinc is commonly detected in the aquatic environment with its widely use in industry [10]. Considering its toxicity and nonbiodegradability, it is necessary to effectively remove zinc. Current main zinc removal techniques from aqueous solutions include physico-chemical precipitation, ion exchange, complexation, adsorption, electrodialysis, etc. [11,12,13]
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