Isotherms, kinetics and thermodynamic studies of adsorption of Cu2+ from aqueous solutions by Mg2+/K+ type orange peel adsorbents

J Hazard Mater. 2010 Feb 15;174(1-3):756-62. doi: 10.1016/j.jhazmat.2009.09.116. Epub 2009 Sep 30.

Abstract

Orange peel (OP) was used as raw material to prepare two novel adsorbents: MgOP (Mg(2+) type orange peel adsorbent) and KOP (K(+) type orange peel adsorbent). FTIR and SEM were used to characterize the adsorbents. Effects of pH, solid/liquid ratio, time and metal ion concentration on the Cu(2+) adsorption by these two adsorbents were investigated. The isotherms data were analyzed using the Langmuir, Freudlich, Temkin and Dubinin-Radushkevich models. Langmuir model provides the best correlation for the adsorption of Cu(2+) by both MgOP and KOP, and the mono-layer adsorption capacity for Cu(2+) removal by MgOP and KOP are 40.37 and 59.77 mg/g, respectively. The adsorbed amounts of Cu(2+) increased with the increase in contact time and reached equilibrium within 20 min. The kinetics data were analyzed using four adsorption kinetic models: the pseudo-first and second-order equations, the Elovich equation and intraparticle diffusion equation. Results show that the pseudo-second-order equation fits the experimental data very well. Thermodynamic studies showed the spontaneous and exothermic nature of the adsorption of Cu(2+) by MgOP and KOP.

MeSH terms

  • Adsorption
  • Citrus sinensis*
  • Copper / chemistry*
  • Hydrogen-Ion Concentration
  • Kinetics
  • Magnesium / chemistry*
  • Microscopy, Electron, Scanning
  • Models, Theoretical
  • Potassium / chemistry*
  • Solutions
  • Spectroscopy, Fourier Transform Infrared
  • Thermodynamics
  • Water

Substances

  • Solutions
  • Water
  • Copper
  • Magnesium
  • Potassium