Removal of lead(II) from aqueous solutions using pre-boiled and formaldehyde-treated onion skins as a new adsorbent

Cafer Saka, Ömer Şahin*, Halil Demir, Mustafa Kahyaoǧlu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

48 Citations (Scopus)


The adsorption characteristics of Pb2+ on pre-boiled treated onion skins (PTOS) and formaldehyde-treated onion skins (FTOS) were evaluated. The effects of Pb2+ initial concentration, agitation rate, solution pH, and temperature on Pb2+ adsorption were investigated in batch systems. Pb2+ adsorption was found to increase with increase in initial concentration. The point of zero net charge (PZC) was 6.53. The optimum pH for the maximum removal of Pb2+ was 6.0. The adsorption equilibrium data was best represented by the Langmuir isotherm model for FTOS and the Freundlich isotherm model for PTOS. The maximum amounts of Pb2+ adsorbed (qm), as evaluated by the Langmuir isotherm, was 200 mgg-1 for FTOS. The efficiencies of PTOS and FTOS for Pb2+ removal were 84,8.0% and 93.5% at 0.15 g/200mL-1 adsorbent dose, respectively. (C0=50 mg L-1). Study concluded that onion skins, a waste material, have good potential as an adsorbent to remove toxic metals like Pb2+ from water. Boehm titration analysis was conducted to determine the surface groups. It was found that the adsorption kinetics of Pb2+ obeyed pseudo-first-order kinetic model as based on Δq (%) values. FTIR and SEM images before and after adsorption was recorded to explore changes in adsorbent-surface morphology. Activation energy (Ea) was obtained as 25.596 kJ/mol.

Original languageEnglish
Pages (from-to)507-517
Number of pages11
JournalSeparation Science and Technology
Issue number3
Publication statusPublished - Jan 2011
Externally publishedYes


  • Adsorbent
  • Adsorption
  • Isotherm
  • Kinetic
  • Onion skin
  • Pb


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