In this study, coconut coir pith (cellulose-lignin compound) was first treated with water and sodium hydroxide solution to remove lignin and impurities, then lignin-extracted coir pith was calcined at 200°C for 6 h. The obtained absorbent was applied to remove Cr(IV) ions by using adsorption method. Some analytical methods such as thermal gravimetric analysis (TGA), Fourier Transform Infrared Spectroscopy (FT-IR), Brunauer–Emmett–Teller analysis (BET), X-ray powder diffraction analysis (XRD),

more »

... pzc analysis, Boehm titration and potentiometric titration were employed to characterize structure, specific surface area, functional groups and surface charge of the absorbent. Adsorption results showed that 95.23% of Cr(IV) was removed from solution of 100 mg.L-1 by using certain amount of absorbent at pH 2.0 within 20 min at room temperature. Kinetics of Cr(VI) adsorption from aqueous solution on absorbent fit to Pseudo-second-order kinetic equation and adsorption isotherm of Cr(IV) followed to Freundlich model.