Adsorption of Hg(II) in aqueous solutions using mercapto-functionalized alkali lignin

A novel adsorbent for Hg(II), mercapto-functionalized alkali lignin (AL-SH) was synthesized by Friedel–Crafts alkylation reaction and nucleophilic substitution reactions. The adsorbent was characterized by the techniques of Fourier transform-infrared spectroscopy (FT-IR), elementary analysis and thermogravimetric analysis, and N 2 adsorption techniques. The effect of various parameters on Hg(II) adsorption process such as initial pH, contact time, ionic strength, initial Hg(II) concentration, temperature, and adsorbent dosage were investigated in detail through batch static experiments. The results indicated that the adsorption process of Hg(II) on AL-SH was mainly dependent on the pH and the optimal pH value was at pH ranging from 4.0 to 6.0. The adsorption process was found to follow pseudosecond-order kinetics and the main process was chemical adsorption, which equilibrated at 8 h. The adsorption isotherm was better described by Langmuir and Temkin isotherm equations compared to Freundlich isotherm equation and the maximum adsorption capacity obtained was 101.2 mg g −1 (pH = 4.0, 20°C, initial Hg(II) concentration was 200 mg L −1 ). The thermodynamic parameters of and were positive while was negative, revealed that the adsorption of Hg(II) onto AL-SH was a spontaneous and endothermic process with increased entropy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131 , 40749.