Removel of malachite green on a bio-adsorbent derived from Walnut shells: characterization, Kinetic and isotherm study

Abstract

The sorption of malachite green (MG) in aqueous solution using Walnut shells was carried out in batch mode. Powder of Walnut shells was prepared within a size between 100 and 250 µm. The Walnut shells was characterized by Fourier Transform infrared spectra (FTIR), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and pH_pzc. Batch experiments were conducted to study the effect of different operating parameters such as contact time, pH, stirring speed, temperature, adsorbent dose and initial MG concentration on the adsorption of MG by Walnut shells. The results showed that the maximum adsorption capacity was 3.06 mg g⁻¹ at pH 6,8, adsorbent dose of 3 g L⁻¹ and initial MG concentration of 10 mg L⁻¹. The equilibrium data were analyzed using two isotherm models such as Langmuir and Freundlich by linear method. A satisfactory correlation coefficient value of the Langmuir isotherm demonstrates that the MG adsorption by Walnut shells is monolayer physical adsorption. The kinetic studies showed that the experimental data were best describing by pseudo- second-order model.