Luong Huynh Vu Thanh * , Cao Luu Ngoc Hanh , Tran Nguyen Phuong Lan , Tran Thi Bich Quyen and Ha Quoc Nam

* Corresponding author (

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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), pHpzc 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.
Keywords: Adsorbent, adsorption, Cr(VI) ion, coir pith

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