Hexavalent chromium removal by various adsorbents: Powdered activated carbon, chitosan, and single/multi-walled carbon nanotubes

Chanil Jung, Jiyong Heo, Jonghun Han, Namguk Her, Sung Jae Lee, Jeill Oh, Jaena Ryu, Yeomin Yoon

Research output: Contribution to journalArticlepeer-review

303 Scopus citations

Abstract

The adsorption behavior of ppb-level aqueous solutions of hexavalent chromium [Cr(VI)] on four different adsorbents was investigated as a function of pH, contact time, initial Cr(VI) concentration, adsorbent dose, and the copresence of competing anions. The adsorbents selected were powered activated carbon (PAC), chitosan, single-walled carbon nanotubes (SWNTs), and multi-walled carbon nanotubes (MWNTs). Each adsorbent was characterized by Fourier transform infrared spectroscopy and measurements of zeta potential to determine its suitability for Cr(VI) adsorption. The adsorption of Cr(VI) was found to be favored at low pH because all adsorbents were positively charged under acidic conditions (pH 4), while a dosage of 100 mg/L resulted in efficient adsorption behavior. PAC and chitosan provided the best removal performance. The highly functionalized and porous PAC and the protonated amines on chitosan enabled a better performance and resulted in high Cr(VI) removal efficiencies of 99.4% and 94.7%, respectively, while the removal efficiencies of SWNTs and MWNTs were 72.9% and 51.9%, respectively. Isotherm and kinetic studies were undertaken to evaluate the characteristics of the Cr(VI) adsorption process. A well-fitted Langmuir isotherm model suggested that monolayer adsorption was the main process operating with an adsorption capacity (qm) of 46.9, 35.6, 20.3, and 2.48 mg/g for PAC, chitosan, SWNTs, and MWNTs, respectively. Pseudo second-order fitted models revealed the importance of kinetic parameters (apart from adsorption capacity) in understanding the transport of Cr(VI) in the solution, while an intra-particle diffusion model fitted well for μg/L levels of Cr(VI) adsorption. This indicated that both physisorption and chemisorption were dominant, particularly for SWNTs. Anions such as Cl- and SO42- in the solution competed with HCrO4- and this phenomenon resulted in negative effects on Cr(VI) adsorption.

Original languageEnglish
Pages (from-to)63-71
Number of pages9
JournalSeparation and Purification Technology
Volume106
DOIs
StatePublished - 2013

Bibliographical note

Funding Information:
This research was supported by the Korea Ministry of Environment, ‘Project, 414-111-004’ and ‘GAIA Project, 2012000550022’.

Keywords

  • Chitosan
  • Hexavalent chromium
  • Multi-walled carbon nanotubes
  • Powdered activated carbon
  • Single-walled carbon nanotubes

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