ADSORPTION OF METHYLENE BLUE DYE BY STIPA TENACISSIMA L (ALFA FIBERS) IN AQUEOUS SOLUTION: EQUILIBRIUM, THERMODYNAMICS, KINETIC MECHANISM

Abstract

As natural and low-cost material, Stipa tenacissima L. fibers were used as an adsorbent to remove methylene blue from aqueous solutions. Alkaline procedure was used to remove non-cellulosic substances to improve sorptive capacity by changing fiber morphology which was analyzed by FTIR, X-ray diffraction, ATG and SEM. A mesoporous structure was developed and the specific surface (SBET) was notably increased from ~3 to 62.48 m2/g. Batch sorption show that equilibrium was obtained with: 5 g/L of fibers after 40 min at 30°C, the adsorbed dye amount increases with increasing pH. The removal rate was about 99.11%. Experimental data were well described by Freundlich isotherm model; while adsorption kinetic constants fitted with the pseudo-second order one. The adsorption thermodynamics and isotherms found to be consistent with a spontaneous exothermic physic-sorption reaction (negative value of ΔH° < 20K Joule/mole). Alfa fibers could be used advantageously to eliminate methylene blue from aqueous solutions.