Effect of acid and alkali treatments of a forest waste, Pinus brutia cones, on adsorption efficiency of methyl green

ABSTRACT

The removal of methyl green (MG) dye from aqueous solutions using acid- or alkali-treated Pinus brutia cones (PBH and PBN) waste was investigated in this work. Adsorption removal of MG was conducted at natural pH, namely, 4.5 ± 0.10 for PBH and near 4.8 ± 0.10 for PBN. The pseudo-second-order model appeared to be the most appropriate to describe the adsorption process of MG on both PBN and PBH with a correlation coefficient R² > 0.999. Among the tested isotherm models, the Langmuir isotherm was found to be the most relevant to describe MG sorption onto modified P. brutia cones with a correlation factor R² > 0.999. The ionic strength (presence of other ions: Cl⁻, Na⁺, and SO₄²⁻) also influences the adsorption due to the change in the surface properties; it had a negative impact on the adsorption of MG on these two supports. A reduction of 68.5% of the adsorption capacity for an equilibrium dye concentration Ce of 30 mg/L was found for the PBH; while with PBN no significant influence of the ionic strength on adsorption was observed, especially in the presence of NaCl for dye concentrations superior to 120 mg L⁻¹.

GRAPHICAL ABSTRACT

KEYWORDS:

• Adsorption
• dyes
• forest waste
• isotherms
• kinetics
• Pinus brutia cones