Chemistry activation of sawdust activated carbon for dye removal: Kinetics and isotherms

Activated carbon based on mesquite sawdust (MGAC) was prepared and characterized to remove methylene blue (MB). The MGAC main attraction is its simplicity, high efficiency, and cost. MGAC use implies an economical and eco-friendly material that costs 4 to 15 times cheaper than commercial carbons. The cost difference is essential when an adsorbent is required in large volumes. MGAC physicochemical characteristics were evaluated determining functional groups (Fourier Transform infrared spectroscopy: FTIR), surface (Scanning electron microscopy: SEM), Specific surface area: Sbet, and crystallinity (X-ray diffraction: XRD), and elemental analysis. MB dye removal using MGAC and commercial active carbons (CACs) was studied by discontinuous adsorption by varying the amount of adsorbent (0.25 to 4 g) with a 10 mg L -1 MB concentration. The information obtained from the experiments was adjusted to Pseudo first and Pseudo second order, as well as intraparticle diffusion kinetic models. Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms were used to estimate the adsorption capacity. The first-order model was the best result for masses of less than 1 g, and the second-order model for masses greater than 1 g. Langmuir isotherm is the best fit, with chemical adsorption with 1.76 mg g -1 vs 3.98 mg g -1 for MGAC and CACs. • Activated carbon based on mesquite sawdust (MGAC) was suitable for MB adsorption • Langmuir isotherm is the best fit, indicating monolayer chemical adsorption with 1.76 mg g -1 • No significant differences were found between CAC and MGAC in dye adsorption • MGAC exhibit a porous surface with lines and wrinkles what could benefit adsorption