Adsorption of Organic Dyes on Lignophenol under Heterogeneous Conditions

抄録

Lignophenol is a phenolic lignin-based polymer with 7,7-bis(aryl)propane-8-O-4'-arylether-9-ol type main structures. This polymer has been synthesized directly from lignocellulosics through the phase-separation system. In order to demonstrate both properties and mechanisms of adsorption on lignophenol and on its derivatives under heterogeneous conditions, investigations for adsorption of three cation-type dyes, Methylene Blue (MB), Brilliant Green (BG) and Crystal Violet (CV) were carried out. Both Hinoki cypress-lignophenol (p-cresol type, HCLC) and composites of HCLC with nano-sized TiO₂ particles (HCLC/ST01) quickly adsorbed these dyes. Isothermal adsorption plots for both HCLC and HCLC/ST01 demonstrated good agreements with a Langmuir plots with r = 0.991 and 0.997, respectively. These results indicated mechanism of these adsorptions followed simple adsorption mechanism with single layer on the surfaces of HCLC and HCLC/ST01. Moreover several HCLC derivatives were demonstrated different behaviors of both adsorption and desorption due to their particular structures. Especially both a second derivative-II of HCLC (HCLC170), which was derived with 170 ℃ treatment in alkaline medium, and Hinoki cypress-lignophenol (pyrogallol type, HCLPyr) demonstrated best adsorptions of MB. Besides, 40-60 % of adsorption of acetylated HCLC indicated that there at least two adsorption sites for dyes such as hydrophilic hydroxyl groups and hydrophobic aromatic groups. In addition, HCLC/ST01 released BG in organic media but other adsorbents included activated carbon has not released at all. These results indicated that control of both adsorption and desorption of various organic compounds can be carried out on demands in aqueous conditions.