Nanoscale zero-valent iron for the removal of Zn2 +, Zn(II)–EDTA and Zn(II)–citrate from aqueous solutions

• Removal of ionic and complexed Zn(II) species from aqueous solutions by nZVI was studied.
• Conditions for mutual removal of Zn2 +, Zn(II)–EDTA and Zn(II)–citrate were examined.
• Untreated, silica-fume supported, and choline dispersed nZVI were used at pH 5–7.
• Zn2 +, Zn(II)–EDTA and Zn(II)–citrate were effectively removed by untreated nZVI.
• At pH 5 simultaneous removal of ionic and complexed Zn(II) species by nZVI is possible.

The parameters which influence the removal of different zinc (Zn) species: Zn2 +, 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. Zn2 +, Zn(II)–EDTA and Zn(II)–citrate were the most effectively removed from aqueous solutions by untreated nZVI. Zn2 + removal was governed mainly by adsorption onto precipitated iron oxides. Complete removal of Zn2 + 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 Zn2 + was completely removed from the solution by adsorption onto iron oxides.