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Mechanistic insight into pH-dependent adsorption and coprecipitation of chelated heavy metals by in-situ formed iron (oxy)hydroxides

Journal of Colloid and Interface Science, ISSN: 0021-9797, Vol: 608, Issue: Pt 1, Page: 864-872
2022
  • 23
    Citations
  • 0
    Usage
  • 28
    Captures
  • 0
    Mentions
  • 0
    Social Media
Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    23
    • Citation Indexes
      23
  • Captures
    28

Article Description

Fe(III) coagulation-precipitation process has been widely used to remove heavy metals from industrial effluents; however, the influences of organic ligands on the sequestration of different heavy metals in the Fe(III)/metal-EDTA ternary system are not well understood. In this study, the pH-dependent mechanisms of Cu II -EDTA and Ni II -EDTA removed by in-situ formed iron (oxy)hydroxides were studied using surface complex modeling and a suite of characterization techniques. Results of surface complex model indicated that there should be minimal difference between removal of Cu II -EDTA and Ni II -EDTA by iron (oxy)hydroxides if adsorption was the dominant mechanism. However, through the speciation analysis and characterization of the precipitates generated after coagulation and precipitation, we have demonstrated that at neutral pH the complexation of Fe(III) and EDTA influenced the surface properties of iron (oxy)hydroxides formed, with the higher removal of Cu 2+ (compared to Ni 2+ ) contributed by its coprecipitation with Fe(III). Moreover, at basic pH, decomplexation of Cu II -EDTA occurred on the iron (oxy)hydroxides surface with the released copper ions involved in the formation of (oxy)hydroxides. The low removal of nickel (from Ni II -EDTA) was ascribed to the higher conditional stability constant of Ni II -EDTA. Results of this study have advanced our understanding of the complicated interactions among Fe(III), organic ligands and heavy metals in the industrial effluents, and provide insight to optimization of the process efficiency.

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