Comprehensive investigation of Basic Red 46 removal by pinecone adsorbent: experimental, isotherm, kinetic and thermodynamic studies

Abstract

In this study, pinecone sawdust (PCS) performance was investigated for Basic Red 46 (BR 46) dye adsorption from aqueous solutions. The physicochemical and morphological characterization of PCS before and after BR 46 adsorption were evaluated with the help of Fourier transform infrared spectra, X-ray diffraction and scanning electron microscopy/energy-dispersive X-ray spectroscopy analysis. Effects of initial dye concentration, temperature and contact time were determined for BR 46 adsorption. Seventeen equilibrium isotherm models and eight kinetic models were compared at 298 K, 308 K and 318 K temperatures for five different concentrations which varied from 20 to 60 mg/L. The obtained adsorption data best-fit the Freundlich model among all the applied isotherm models, and the maximum adsorption capacity (q(m)) was calculated as 129.87 mg/g at 298 K. The pseudo-second-order model was the best choice to describe the adsorption behavior among all the applied kinetic models. The removal percentage of BR 46 dye with PCS was 74.52% at 318 K for 60 mg/L concentration. The negative free energy (Delta G degrees), enthalpy (Delta H degrees) and entropy (Delta S degrees) values of adsorption were calculated as - 2837 kJ/mol, 18,898 kJ/mol and 68.51 J/mol K, respectively. This adsorption process was spontaneous and favorable, coinciding with the negative free energy. The activation energy (E-A) value of this process was determined with the Arrhenius equation as 19.92 kJ/mol. The reliability of all results was analyzed statistically and evaluated with correlation coefficient (R-2), sum of squares, sum of the square of error and mean square of error values. As a result of this study, PCS can be used effectively for BR 46 dye removal. [GRAPHICS] .