The parameters which influence the removal of different zinc (Zn) species: Zn(2+), Zn(II)-EDTA and Zn(II)-citrate from aqueous solutions by nanoparticles of zero-valent iron (nZVI) were investigated at environmental relevant pH values. Untreated, surface modified and silica-fume supported nZVI were applied at different iron loads and contact times to Zn solutions, which were buffered to pH 5.3, 6.0 and 7.0. The results revealed that pH, the type of nZVI, the iron load, the contact time, and the Zn species all had a significant influence on the efficiency of removal. Zn(2+), Zn(II)-EDTA and Zn(II)-citrate were the most effectively removed from aqueous solutions by untreated nZVI. Zn(2+) removal was governed mainly by adsorption onto precipitated iron oxides. Complete removal of Zn(2+) and Zn(II)-citrate was obtained at all pH values investigated. The removal of strong Zn(II)-EDTA complex was successful only at acidic pH, which favored degradation of Zn(II)-EDTA. Consequently, the released Zn(2+) was completely removed from the solution by adsorption onto iron oxides.
Keywords: Aqueous solutions; Nanoparticles of zero-valent iron; Remediation; Zn(2+); Zn(II)–EDTA; Zn(II)–citrate.
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