Use of refuse-derived fuel waste for the adsorption of 4-chlorophenol and dyes from aqueous solution: Equilibrium and kinetics

• Highly porous carbon adsorbents are prepared from refuse-derived fuel (RDF-5) waste.
• NaOH-activated RDF-5 adsorbents exhibit good adsorption ability for phenol and dyes.
• Various equilibrium and kinetic models are fitted to the data by nonlinear regression.
• Similarity index between the Sips and Langmuir or Freundlich equations is proposed.

Porous carbons with surface area of 898 and 1461 m2 g−1 were prepared from refuse-derived fuel (RDF-5) waste via NaOH activation at 780 °C and a NaOH/char weight ratio of 1 (RDFN1) and 2 (RDFN2), respectively. Changes in surface morphology and chemical compositions of the carbons were studied by SEM and elemental analysis. The ability of these carbons for the adsorption of 4-chlorophenol (4-CP), acid blue 74 (AB74), and methylene blue (MB) from aqueous solution were examined. Various isotherm (Frenudlich, Langmuir, and Sips) and kinetic (pseudo-first-order, pseudo-second-order, and Elovich) equations were fitted by nonlinear regression using SigmaPlot 11 software. It was shown that the pseudo-second-order equation best described adsorption of 4-CP and AB74 on RDFN2, whereas Elovich equation best followed adsorption of three solutes on RDFN1. The similarity index between the Sips and Langmuir or Freundlich equations was finally proposed from isotherm parameters obtained based on 59 adsorption systems.