Mechanism investigation and surface complexation modeling of zinc sorption on aluminum hydroxide in adsorption/coprecipitation processes

Chiharu Tokoro, Taisuke Sakakibara, Shinya Suzuki

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)

Abstract

The sorption mechanism of dilute Zn [initial Zn(II) concentration up to 40mgdm-3] on aluminum hydroxide was investigated. Adsorption and coprecipitation at pH 7 were compared. The adsorption process gave a Langmuir-type isotherm and the zeta potential of Zn(II)-adsorbed aluminum hydroxide decreased linearly with increasing sorption density of Zn on aluminum hydroxide. The adsorption mechanism is therefore mainly surface complexation. In contrast, in the coprecipitation process, a Brunauer-Emmett-Teller like isotherm was obtained; the slope of the zeta potential versus Zn(II) sorption density decreased when the initial Zn/Al molar ratio was greater than 0.5. The X-ray diffraction pattern of Zn(II)-coprecipitated aluminum hydroxide changed from that of poorly crystalline gibbsite to a Zn-Al layered double-hydroxide (LDH) when the initial Zn/Al molar ratio was greater than 0.5, showing that surface complexation was the main sorption mechanism, but surface precipitation of Zn-Al LDH was also involved when the initial Zn/Al molar ratio in the coprecipitation process was greater than 0.5. A quantitative diffuse-layer model was constructed. The aluminum hydroxide exchange capacity was set at 0.61molmol-Al-1, based on the experimentally determined surface area, 340m2g-1. Surface complexation coefficients for H+, OH-, and Zn(II) adsorption on aluminum hydroxide were determined by fitting to the experimental adsorption results. The obtained parameters were in excellent agreement with those previously reported for a database of gibbsite adsorption equilibrium constants. The pH edge for Zn(II) removal by aluminum hydroxide was successfully reproduced by the constructed model.

Original languageEnglish
Pages (from-to)86-92
Number of pages7
JournalChemical Engineering Journal
Volume279
DOIs
Publication statusPublished - 2015 Nov 1

Keywords

  • AMD
  • DLM
  • ICP-AES
  • LDH
  • Poorly crystalline gibbsite
  • Surface precipitation
  • Wastewater treatment
  • XRD
  • Zeta potential
  • Zn-Al LDH

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry
  • Chemical Engineering(all)
  • Industrial and Manufacturing Engineering

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