Inhomogeneous complexation of trace metals in water with organic nano-complexants

Bella Dolgin, Valery Bulatov, Hodayah Hadar-Abuhatzira, Julia Japarov, Israel Schechter*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

The complexation of heavy metals, such as Cd2+ and Ni 2+, with organic complexants such as 1-(2-pyridylazo)-2-naphthol (PAN) and 1-(2-thiazolylazo)-2-naphthol (TAN) in water has been investigated. Under such conditions, both the reagents and the products form nano-particulates. These materials are important because their spectrum changes upon exposure to heavy metals and they may be used for design of new optical detectors. The kinetic schemes so far suggested for these complexation reactions are not valid for such experimental conditions, since they assume homogeneous behavior. We provide evidences to the inhomogeneous nature of these reactions. The complexation has been studied using TEM imaging, zeta-potentiometry, time-dependent particulate size analysis and time-dependent spectroscopy. Many of the experimental results are explained in terms of the nature of the nano-particulates of these two complexants. Several processes were identified, including crystal growing of the complexant, its reaction with metal ions in solution and on the surface area, chemical erosion of complexant crystallites and their decomposition, re-crystallization of the formed complexes and long term aggregation of both the complexant and the resulted complex. It was found that the needle-like nano-structures on the surface of the TAN particulates governs its reaction and particulate behavior. The known optimal complexation conditions, such as pH, and delay time are now understood in terms of the zeta-potential minima of the suspensions and in terms of the kinetic parameters. Also the interferences of some ions in the Ni-TAN complexation are now quantified and the kinetic data indicate the best delay time when the interfering effects are minimal.

Original languageEnglish
Pages (from-to)391-398
Number of pages8
JournalOptical Materials
Volume34
Issue number2
DOIs
StatePublished - Dec 2011
Externally publishedYes

Keywords

  • Complexation
  • Heavy metals
  • Nanoparticles
  • Spectral detection
  • Water

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