Application of lignin extracted from fibers and aminated lignin in anionic dyes contaminated water remediation.

In this paper, lignin was chemically extracted from fibers and modified with branched polyethyleneimine (BPEI) and the resulting samples were applied for the adsorption of two anionic dyes; Acid red 183 (AR183) and Acid blue 25 (AB25) from aqueous suspension. Analytical characterization methods including SEM, FT-IR, TGA/DTG, and XRD were used to analyze the studied samples. The images of the extracted lignin displayed a rough feature. After functionalization of lignin with branched polyethyleneimine, the surface became rougher with the presence of many cavities. FT-IR spectrum of the extracted lignin showed series of absorption peaks characteristics of lignin structure. The XRD diffractograms revealed a wide area under the curve, confirming the amorphous characteristic of the lignin samples. The functionalization with branched polyethyleneimine does not affect the crystallinity of lignin. TGA/DTG exhibited several degradation stages in a wide range of degradation temperature due to the complex molecular structure of lignin. The thermal decomposition of the modified lignin samples occurred at more elevated temperature values compared to unmodified extracted lignin. At adsorption equilibrium (pH = 5, time = 60 min, and  = 19 °C), the highest adsorption capacities reached using the adsorbent lignin-BPEI (5%) were 192 and 135 mg/g for AB25 and AR183, respectively. The adsorption process fitted well to pseudo second order and Freundlich equations. Overall, the prepared aminated lignin was found to be excellent candidate for the decolorization of water rich with anionic dyes.