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The chemical structures of lignocresols derived from native lignins by the phase-separative treatment with cresol and sulfuric acid were characterized by spectral analyses and chemical degradations. The changes in the structure of lignin during the conversion process were discussed. Lignocresol had few conjugated systems, being pinkish white, its brightness comparable to milled wood lignin. Spruce lignocresol included 0.64mol/C9 of cresolic nuclei in the molecule (0.9mol/C9 in birch lignocresol), 77% of which were linked to lignin Cα-positions through carbon-carbon linkages, 16% possibly to Cy-positions, and the remaining 7% etherified to lignin side chains through its phenolic hydroxyl groups. The molecular weight (Mw) of lignocresol was ca. 3500 in spruce, lower in birch. Most of the β-and γ-positions in the side chains of Cg units remained intact, except the coniferyi alcohol and aldehyde units. These structural features were constant during the reaction time up to 60min. It is concluded that the fragmentation of lignin in the phase-separative reaction system was principally due to the cleavage of benzyl aryl ethers, and the skeleton of lignocresol represents those of lignin subblocks formed by the dehydrogenative polymerization of monolignols.

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Conventional metallurgical processing of precious metals involves the use of large amounts of toxic chemicals. Realizing a need to develop environmentally benign metallurgical technology for precious metals, we prepared two types of adsorption gels, containing primary amine and ethylenediamine functional groups and abbreviated as PA−lignin and EN−lignin, respectively, from wood powder. Both of these adsorption gels were found to be effective for the adsorption of Au(III), Pd(II), and Pt(IV) from weak to strong hydrochloric acid media. In contrast, base metals such as Cu(II), Fe(III), Ni(II), and Zn(II) were almost not adsorbed on either gel. The above-mentioned precious metals were adsorbed on the gels according to the Langmuir adsorption model, and the highest maximum adsorption capacity was observed for Au(III). The formation of ion pairs of metal−chloro complex anions and protonated adsorption gels in acidic media was proposed to be the main adsorption process. However, in the case of Au(III) adsorption, a reductive adsorption mechanism was confirmed to occur by reference to XRD spectra and SEM images of the gels obtained after adsorption.