Abstract
Cr(VI), a serious threat to human health, widely exists in the effluents of various industrial processes. In this paper, the potential of industrial lignin for efficient removal of Cr(VI) from wastewater was systematically investigated, including pulping black liquor lignin (BLN), enzymolysis lignin (ELN), and SPORL pretreatment spent liquor (FS). The structure characterizations of three lignins were investigated by thermogravimetry (TG), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) surface area measurement, scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). Among these three lignins, BLN showed the highest adsorption amount of Cr(VI) and good selectivity in wastewater simulation. According to the Langmuir model, the calculated maximum adsorption amount of Cr(VI) on ELN, BLN, and FS was 801.57, 864.30, and 642.26 mg g-1, respectively. The adsorption of Cr(VI) by industrial lignins was a chemisorption process, during which Cr(VI) was reduced to low-toxic Cr(III). This paper provided a promising application for the effective utilization of industrial lignins.
Highlights
Cr(VI), as a common heavy metal ion, is highly toxic, carcinogenic and non-degradable (Zhang et al 2018)
Enzymolysis lignin was kindly provided by Shandong Longlive Bio-technology CO., Ltd. (Shandong, China)
The black liquor lignin (BLN) or enzymolysis lignin (ELN) was obtained by filtration and dried at 60 °C
Summary
Cr(VI), as a common heavy metal ion, is highly toxic, carcinogenic and non-degradable (Zhang et al 2018). The second largest natural polymer after cellulose, is a highly branched and complex polymer It contains p-hydroxybenzene (H), guaiacyl (G) and syringyl (S) phenylpropane units, while the composition and quantity of the units vary with the species of plants and industrial processes. The potential of industrial lignins for efficient removal of Cr(VI) from aqueous solution were investigated. Three different types of lignins, namely pulping black liquor lignin (BLN), enzymolysis lignin (ELN), and SPORL pretreatment spent liquor (FS), were employed as adsorbents. The removal efficiency and adsorption performance for Cr(VI) of these three lignins were systematacially studied, including: i) the effect of adsorption time, original metal concentration, and temperature on adsorption process; ii) adsorption isotherm, thermodynamics, and kinetics; iii) wastewater simulation, Cr species changes during adsorption, and potential adsorption mechanism
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