Walnut bloom powder as a waste-based sorbent for cationic dyes removal: equilibrium, kinetic, and thermodynamic studies

In the present study, for the first time, walnut bloom (WB) powder was used as a natural and economic sorbent for the removal of methylene blue (MB) from an aqueous solution. This new biosorbent was characterized using the following techniques: scanning electron microscopy (SEM), X-ray diffraction (XRD), COHNS, BET (Brunauer-Emmett-Teller) analysis and Fourier transform infrared (FTIR) spectroscopy. MB removal efficiency and its adsorption onto WB powder were tested in a batch system by varying parameters such as initial dye concentration, contact time, pH, temperature, and dosage of biosorbent in which the removal percentages of ∼92% was achieved under the optimum conditions. Equilibrium data and adsorption isotherms fitted well with the Langmuir model (R2= 0.999, 0˂RL˂1) with a maximum monolayer adsorption capacity of 46 mg g-1. The chemical kinetics of MB adsorption followed the pseudo-second-order model. Also, the magnitude of thermodynamic functions identified the removal of MB. ΔH of -7.32 kJ mol-1 and ΔS of -4.32 kJ mol-1 indicated the spontaneity, exothermicity, and favorability of the adsorption process at room temperature.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author